| genomes of endogenous and exogenous avian retroviruses. | the endogenous viruses of chickens are closely related to the exogenous avian leukosis viruses (alv) yet as a group differ from these viruses in their host range, growth rate, and oncogenicity. the present study was undertaken to determine the patterns of relationship among the genomes of endogenous and exogenous alvs. complete or partial t1 oligonucleotide maps were prepared from the genomes of endogenous viruses that reside at eight distinct loci in chickens. selected endogenous viruses and re ... | 1983 | 6302996 |
| studies of reticuloendotheliosis virus-induced lymphomagenesis in chickens. | seventy-three percent of chickens inoculated with the chick syncytial strain of reticuloendotheliosis virus (rev) at hatching developed lymphomas by 39 weeks of age. neonatal treatment with cyclophosphamide or surgical bursectomy at 2, 4, 8, or 12 weeks of age significantly (p less than 0.01) reduced lymphoma development. in a further experiment, surgical bursectomy of rev-infected chickens followed by intravenous inoculation of the chickens with a single cell suspension of their own bursa cells ... | 1983 | 6303293 |
| b5 and b15 associated with progressive marek's disease, rous sarcoma, and avian leukosis virus-induced tumors in inbred 15i4 chickens. | rprl 15i4 inbred chickens are nearly histocompatible except for the b5 and b15 haplotypes that determine the major transplantation antigens. b5b5 and b15b15 15i4 chickens were equally and highly susceptible to tumors induced by marek's disease, rous sarcoma, or avian leukosis viruses (alv), suggesting both of these haplotypes may determine a general influence leading to tumor development. the 15i4 birds were highly susceptible to erythroblastosis, and most developed immunological tolerance to th ... | 1983 | 6306630 |
| immunological phenotype of lymphomas induced by avian leukosis viruses. | the production of immunoglobulin by six cell lines derived from bursal tumors induced by avian leukosis virus follows two general patterns: (i) three cell lines that have been extensively passaged in culture synthesize and secrete light chains only; (ii) three cell lines that are recently isolated produce and secrete monomeric immunoglobulin m in addition to free light chains. all six cell lines synthesize and secrete both glycosylated and unglycosylated forms of light chain. we conclude that th ... | 1983 | 6308424 |
| evidence that avian tumour virus-immune chicken sera recognize only viral structural antigens on the surface of avian tumour virus-infected cells. | the specificity of the humoral response of chickens to avian tumour viruses (atv) was investigated by reacting atv-immune sera with triton x-100 extracts of uninfected, infected and transformed chicken embryo fibroblasts. analysis of these immune reactions by polyacrylamide gel electrophoresis revealed that avian leukosis virus-challenged and rous sarcoma virus-challenged chickens recognized only two major cell surface antigens of 100000 and 29000 mol. wt. which were present on transformed and n ... | 1983 | 6315863 |
| proviral deletions and oncogene base-substitutions in insertionally mutagenized c-myc alleles may contribute to the progression of avian bursal tumors. | bursal lymphomas induced in chickens by avian leukosis viruses (alvs) harbor proviral insertions that augment expression of an adjacent cellular oncogene, c-myc. to analyze such insertionally mutagenized c-myc genes in greater detail, we isolated molecular clones from two independent tumors. precise proviral integration has occurred within the transcribed region of the c-myc gene in both mutant alleles. the proviruses bear different internal deletions that preclude the expression of the gag, pol ... | 1984 | 6322173 |
| specificity of avian leukosis virus-induced hyperlipidemia. | rous-associated virus 7 (rav-7) is a subgroup c avian leukosis virus which does not transform cells in vitro or carry an oncogene. when injected into 1-day-old hatched chicks, rav-7 causes a low incidence of lymphoid leukosis after a latent period of several months. in contrast, infection of 10-day-old chicken embryos with rav-7 leads to a disease syndrome characterized by stunting, obesity, atrophy of the bursa and the thymus, high triglyceride and cholesterol levels, reduced thyroxine levels, ... | 1984 | 6323732 |
| avian leukosis virus infection: analysis of viremia and dna integration in susceptible and resistant chicken lines. | avian leukosis viruses induce lymphoid leukosis, a lymphoma which develops within the bursa of fabricius several months after virus infection. chickens from the hyline sc and fp lines are, respectively, susceptible and resistant to avian leukosis virus-induced lymphoid leukosis. we examined plasma and cellular dna obtained from avian leukosis virus-infected chickens for the presence of viremia and integrated viral sequences to determine whether the extent of virus infection is comparable in indi ... | 1984 | 6328031 |
| characterization of a rous sarcoma virus mutant defective in packaging its own genomic rna: biological properties of mutant tk15 and mutant-induced transformants. | a mutant derived from a temperature-sensitive mutant of rous sarcoma virus ( tsny68 ) which showed extremely low infectivity was characterized. infection of chicken embryo fibroblast cells with the mutant, tk15 , induced two types of transformants, mutant-producing 15c (+) and nonvirus -producing 15c (-) transformants. 15c (+) cells expressed all four viral genes normally and produced a normal level of virus particles. no complementation was observed between the mutant and avian leukosis viruses ... | 1984 | 6328034 |
| nonspecific integration of the htlv provirus genome into adult t-cell leukaemia cells. | human t-cell leukaemia virus (htlv), previously also reported as atlv, is a recently identified retrovirus which is closely associated with adult t-cell leukaemia (atl) endemic in southwestern japan and the caribbean. determination of the total nucleotide sequence of the htlv genome has revealed no typical onc gene acquired from the cellular sequence. screening of the htlv provirus genome in tumour cells has shown that in all cases of atl examined, the primary tumour cells contained the provirus ... | 1984 | 6328324 |
| differential response to avian leukosis virus infection exhibited by two chicken lines. | infection of susceptible chickens with avian leukosis virus (alv) results in the development of bursal lymphomas. these neoplasms develop within the bursa of fabricius following a latent period of several months. the response exhibited by two previously uncharacterized chicken lines to alv infection has been examined. the two lines, hyline sc and fp, responded differently to alv infection. during a 24-week period following intravenous alv infection, 27 of 50 sc chickens developed bursal lymphoma ... | 1984 | 6328748 |
| yellow fever vaccine and avian leukosis virus. | | 1984 | 6329052 |
| new findings on the congenital transmission of avian leukosis viruses. | rav-0, an endogenous avian leukosis virus, does not undergo congenital transmission in infected k28 chickens. in contrast, avian leukosis viruses of exogenous origin undergo highly efficient congenital transmission. the relative abilities of endogenous and exogenous viruses to undergo congenital transmission appear to be determined by the p27 capsid proteins of these viruses. | 1984 | 6330893 |
| common site of integration of htlv in cells of three patients with mature t-cell leukaemia-lymphoma. | human t-cell leukaemia-lymphoma virus (htlv) was first isolated in the united states from a patient with an aggressive form of cutaneous t-cell lymphoma (ctcl) and was later found associated with clusters of adult t-cell leukaemia-lymphomas (atl) in various parts of the world, including japan and the caribbean. leukaemic cells of the htlv-positive patients seem to be clonal expansions of single infected cells since the provirus(es) are found at the same sites in a given patient. in avian leukosi ... | 1983 | 6341859 |
| transcriptional interference in avian retroviruses--implications for the promoter insertion model of leukaemogenesis. | the downstream (3') long terminal repeat (ltr) of an avian retroviral provirus is unable to act as an efficient promoter of transcription when a transcriptionally active upstream (5') ltr is present. this transcriptional interference may explain the observation that only deleted proviruses have been observed inserted adjacent to c-myc in avian leukosis virus induced lymphomas of chickens. | 1984 | 6363938 |
| characterization of a solitary long terminal repeat of avian endogenous virus origin. | a recombinant lambda phage library constructed with a partial ecor1 digest of dna from a normal rprl line 15b chicken was screened using 32p-labeled plasmid containing rous-associated virus (prav-2). nucleotide sequence analyses of a fragment of one subclone revealed the presence of a solitary long terminal repeat (ltr) that is similar to the ltrs of avian endogenous retroviruses ev1 and ev2. this ltr is flanked by unique 6 bp direct repeats characteristic of the target site for duplication of a ... | 1984 | 6545075 |
| using retroviruses as insertional mutagens to identify cellular oncogenes. | three criteria have been used to identify cellular genes that might play a role in oncogenesis: (i) homology with known viral transforming genes (v-onc's); (ii) activated expression in tumor cells; and (iii) transforming activity in cultured mouse cells. we have been exploring the hypothesis that retroviruses lacking oncogenes activate cellular oncogenes by insertional mutagenesis. our approach is to locate proviruses within the chromosomal dna of clonal populations of tumor cells, and to identi ... | 1983 | 6867028 |
| surface antigens on marek's disease lymphoblastoid tumor cell lines. | a total of 32 marek's disease virus (mdv)-induced cell lines, 1 avian leukosis virus-induced cell line, and 1 reticuloendotheliosis virus (rev)-induced lymphoblastoid cell line were investigated for the presence of fc receptors, surface igm, and ia-like antigen. surface igm and fc receptors could not be demonstrated on any of the cell lines. ia-like antigen was detected on all mdv-induced cell lines and on the 1 rev-induced cell line. ia-like antigen was unrelated to other antigens reported to b ... | 1982 | 6955560 |
| effect of gene dosage on cell-surface expression of thy-1 antigen in somatic cell hybrids between thy-1- abelson-leukemia-virus induced lymphomas and thy-1+ mouse lymphomas. | hybrids between pseudodiploid thy-1.1+ lymphomas and thy 1.2- pseudodiploid abelson-leukemia-virus-induced-(alv-induced) lymphomas express thy-1 glycoprotein on their cell surface. these thy-1+ hybrids invariably express the thy 1.1 allelic form of the glycoprotein and may be either thy 1.2+ or thy 1.2-. sublines expressing both thy 1.1 and thy 1.2 can be isolated from thy 1.1+, thy 1.2- hybrids by cell sorting. in contrast to hybrids with pseudodiploid alv-induced lymphomas, hybrids between thy ... | 1981 | 7203562 |
| proteolytic cleavage at the gag-pol junction in avian leukosis virus: differences in vitro and in vivo. | in avian leukosis virus, processing by the viral protease (pr) appears to activate reverse transcriptase (rt), since pr-defective virions have extremely feeble reverse transcriptase activity. we showed previously that when such detergent-treated virions are digested in vitro with pr, the gag precursor is completely and properly matured, but the gag-pol precursor is not. in particular, the junction between gag and pol, i.e., between the pr and rt domains in gag-pol, remains refractory to cleavage ... | 1994 | 7522375 |
| replication of avian leukosis viruses with mutations at the primer binding site: use of alternative trnas as primers. | we have tested whether avian leukosis viruses (alvs) can use trnas other than trnatrp to initiate reverse transcription. the primer binding site (pbs) of a wild-type alv provirus, which is complementary to the 3' end of trna(trp), was replaced with sequences homologous to the 3' ends of six different chicken trnas (trn(apro), trna(lys), trna(met), trna(ile), trna(phe), and trna(ser)). transfection of these proviruses into chicken embryo fibroblasts resulted in the production of infectious viruse ... | 1995 | 7545245 |
| germline transmission of exogenous genes in chickens using helper-free ecotropic avian leukosis virus-based vectors. | we have used vectors derived from avian leukosis viruses to transduce exogenous genes into early somatic stem cells of chicken embryos. the ecotropic helper cell line, isolde, was used to generate stocks of nl-b vector carrying the neo(r) selectable marker and the escherichia coli lacz gene. microinjection of the nl-b vector directly beneath unincubated chicken embryo blastoderms resulted in infection of germline stem cells. one of the 16 male birds hatched (6.25%) from the injected embryos cont ... | 1995 | 7581517 |
| influence of the alv6 recombinant avian leukosis virus transgene on production traits and infection with avian tumor viruses in chickens. | the biological costs of the alv6 recombinant transgene that in chickens induces dominant resistance to the subgroup a avian leukosis virus (alv), in terms of effects on production traits, were studied. four generations of white leghorn chickens of line tr, segregating for alv6 but free of endogenous viral genes, as well as two generations of crosses between tr and ottawa line wg (wgtr) were tested under a specific-pathogen-free environment. in the birds studied, the transgene appeared unchanged ... | 1995 | 7603962 |
| functional analysis of avian class i (bfiv) glycoproteins by epitope tagging and mutagenesis in vitro. | similarities between the physical structures of avian and mammalian major histocompatibility complex (mhc) class i glycoproteins have been proposed based on comparative alignment of their amino acid sequences. to investigate the physical structure of the chicken class i glycoprotein, we cloned the cdna representing the bfiv locus of the b21 haplotype. a unique, chimeric class i glycoprotein was constructed by incorporating an epitope tag (flag) at the n terminus. monoclonal antibodies to the fla ... | 1995 | 7621880 |
| virofection: a one-step procedure for using replication-defective retrovirus vectors. | virofection is a simple new way to use replication-defective vectors. it consists of the cotransfection of two plasmids: one plasmid bearing the genome of the replication-defective retrovirus vector and a second "helper" plasmid expressing the gag, pol, and env retrovirus sequences. it provides stable integration into the chromosome and long-term expression of only vector-borne sequences. we present here several helper plasmids derived from avian leukosis viruses, which we have used for the viro ... | 1995 | 7645216 |
| in vitro analysis of a primary, major histocompatibility complex (mhc)-restricted, cytotoxic t-lymphocyte response to avian leukosis virus (alv), using target cells expressing mhc class i cdna inserted into a recombinant alv vector. | the interaction between the major histocompatibility complex (mhc) and cytotoxic t lymphocytes (ctls) is an important component of the host's resistance to viral infections and tumor formation. in this study, an avian leukosis virus (alv) vector system, rcasbp, expressing mhc chicken class i (b-f) cdna was used to develop target cells expressing the chicken class i glycoproteins complexed with alv antigens on the cell surface. peripheral blood from chickens inoculated with alv was shown to conta ... | 1995 | 7666545 |
| influence of expression and cis-acting sequences from avian leukosis viruses (alvs) on stability of (alv)-based retrovirus vectors. | defective avian leukosis virus (alv)-based vectors expressing the neo and lacz genes were constructed under the control of cis-acting elements originated from 4 avian retroviruses: avian erythroblastosis virus (aev), rous associated viruses 1 (rav-1) and 2 (rav-2), and the schmidt ruppin strain of rous sarcoma virus subgroup d (sr-rsv-d). we used these vectors to study the long-term stability of beta-galactosidase expression (encoded by the lacz gene) in a permanent cell line from quail fibrobla ... | 1995 | 7671000 |
| influence of sequences in the long terminal repeat and flanking cell dna on polyadenylation of retroviral transcripts. | readthrough transcripts are formed during retrovirus infection by polyadenylation of viral rna in cellular sequences adjacent to the provirus. we have studied such transcripts in avian leukosis virus-infected cell clones containing a single provirus, either the wild type or one with an inactivating mutation in the poly(a) addition signal. all individual wild-type proviruses produced readthrough transcripts, implying that this property is not restricted to a few integration sites. the range of si ... | 1993 | 7690423 |
| latency and reactivation of marek's disease virus in b lymphocytes transformed by avian leukosis virus. | the physical and biological state of the marek's disease virus (mdv) genome in avian leukosis virus (alv)-transformed cells is characterized using cell lines established from alv tumours co-infected with the sb-1 strain of mdv. the mdv genome within the alv-transformed cells was found to be methylated at 5' cpg 3' dinucleotides. less than 2% of the tumour cells expressed mdv antigen and only one virus plaque that was characteristic of an mdv infection was noted when tumour cells were cocultured ... | 1993 | 7691987 |
| reverse transcriptase and protease activities of avian leukosis virus gag-pol fusion proteins expressed in insect cells. | protease (pr)-defective avian leukosis virus particles display 300-fold-reduced levels of reverse transcriptase (rt) activity relative to wild-type particles. this observation suggests that during virion assembly rt is activated by proteolytic maturation of the gag-pol polyprotein precursor. to study the relationship between proteolytic cleavage and rt activation, we subjected pr-defective virion cores to digestion with purified viral pr and analyzed the structure of the major polypeptides produ ... | 1993 | 7693975 |
| characterization of a unique retroviral recombinant containing 7s l sequences. | using a recently described system to generate recombinants between avian leukosis viruses (alv) and cellular neo mrna (a.m. hajjar and m.l. linial, j. virol. 67:3845-3853, 1993), we isolated a recombinant containing 7s l sequences. analysis of this recombinant revealed that it most likely arose during reverse transcription of three copackaged rnas: 7s l rna, neo rna, and alv genomic rna. reverse transcription appears to have initiated on the 7s l rna. a model for the generation of this recombina ... | 1993 | 7693977 |
| mutations in the dna-binding and dimerization domains of v-rel are responsible for altered kappa b dna-binding complexes in transformed cells. | the c-rel proto-oncogene encodes a member of the rel/nf-kappa b family of transcription factors. the oncogenic viral form, v-rel, transduced by avian reticuloendotheliosis virus t, induces lymphoid tumors. v-rel transformation may be mediated directly by binding of v-rel to cognate dna sites, resulting in altered gene expression, and/or indirectly by releasing rel/nf-kappa b transcription factors from cytoplasmic retention molecules, resulting in their translocation to the nucleus and the inappr ... | 1995 | 7745683 |
| identification and characterization of the viral interaction determinant of the subgroup a avian leukosis virus receptor. | the cellular receptor for subgroup a avian leukosis viruses (alv-a) has a small, 83-amino-acid extracellular domain containing a motif that is related in sequence to the ligand binding repeats of the low-density lipoprotein receptor. extensive mutagenesis of the alv-a receptor has identified two acidic amino acids (asp-46 and glu-47) and an adjacent aromatic amino acid (trp-48) in the carboxy-terminal portion of this low-density lipoprotein receptor-related motif that are crucial for efficient v ... | 1995 | 7769686 |
| analysis of alv-based packaging cell lines for production of contaminant defective viruses. | we have previously described avian leukosis virus-based packaging cell lines that express gag, pol, and env proteins from two transcomplementing genomes and produce helper-free stocks of retroviral vectors with different host ranges. in this report, we demonstrated that (i) despite the deletion of the psi packaging sequence, the packaging-defective transcomplementing retroviral transcripts were packaged into virions at a level that could reach 2.3% of a wild-type virus packaging level and (ii) d ... | 1995 | 7778301 |
| hprs-103 (exogenous avian leukosis virus, subgroup j) has an env gene related to those of endogenous elements eav-0 and e51 and an e element found previously only in sarcoma viruses. | the avian leukosis and sarcoma virus (alsv) group comprises eight subgroups based on envelope properties. hprs-103, an exogenous retrovirus recently isolated from meat-type chicken lines, is similar to the viruses of these subgroups in group antigen but differs from them in envelope properties and has been assigned to a new subgroup, j. hprs-103 has a wide host range in birds, and unlike other nontransforming alsvs which cause late-onset b-cell lymphomas, hprs-103 causes late-onset myelocytomas. ... | 1995 | 7815543 |
| a serosurvey using enzyme-linked immunosorbent assay for antibodies against poultry pathogens in ostriches (struthio camelus) from zimbabwe. | horseradish peroxidase-conjugated goat anti-ostrich igg was raised and used in commercial enzyme-linked immunosorbent assay kits to detect antibodies reactive with 11 poultry pathogens in sera from 149 ostriches from nine farms around zimbabwe. antibodies were detected to turkey rhinotracheitis virus (99%), newcastle disease virus (23%), avian reovirus (19%), infectious bursal disease virus (15%), avian encephalomyelitis virus (15%), mycoplasma gallisepticum and/or m. synoviae (11%), reticuloend ... | 1994 | 7832718 |
| diseases and management of backyard chicken flocks in chitungwiza, zimbabwe. | to gather information on backyard chicken flocks in chitungwiza, an urban center in zimbabwe, 85 flock owners were interviewed. the mean flock size was 53 birds (range 1-650), and most birds were kept for meat, for either domestic consumption or local sale. mean age at slaughter was 12.4 weeks (range 8-24). none of the owners vaccinated their birds, and reported mortality rates were high (mean 25%), most commonly being associated with diseases causing eye and respiratory problems. most owners co ... | 1994 | 7832719 |
| sequence of host-range determinants in the env gene of a full-length, infectious proviral clone of exogenous avian leukosis virus hprs-103 confirms that it represents a new subgroup (designated j). | a genomic dna library was constructed, in a bacteriophage lambda vector, from line 0 chick embryo fibroblasts (cefs) infected with hprs-103, an exogenous avian leukosis virus (alv; envelope subgroup j) recently isolated from meat-type chickens. the library was screened at high stringency using a full length rav-1 (subgroup a) proviral probe. from 10(6) plaques, two clones which hybridized strongly to the rav-1 probe were isolated; one contained a full-length copy of the proviral genome of hprs-1 ... | 1995 | 7844530 |
| reflections on the pathogenesis of diseases caused by the acute avian leukosis/sarcoma viruses with special reference to avian erythroblastosis. | the various diseases that follow experimental infection with the acute and non-acute avian oncoviruses are discussed with special reference to the pathogenesis of avian erythroblastosis. one view, based on in vitro studies, sees erythroblastosis as the product of a failure in the differentiation of virus-infected stem cells to mature erythrocytes, as a result of cell 'transformation'. the results of some in vivo studies, however, point to a resemblance of the disease to a haemolytic anaemia, whe ... | 1994 | 7863611 |
| defective retroviral endogenous rna is efficiently transmitted by infectious particles produced on an avian retroviral vector packaging cell line. | this report describes the contamination of "helper-free" stocks of defective retroviral vector with particles bearing retroviral endogenous rna. an avian leukosis virus-based packaging cell line was developed from lmh cells that bear the ev1, ev3, and ev6 retroviral endogenous loci. the results show that an endogenous retroviral transcript (ev3) was packaged into virions produced by this packaging cell line and was efficiently transferred along with the vector to target cells. the titer of the e ... | 1995 | 7871738 |
| proteolytic processing of particle-associated retroviral polyproteins by homologous and heterologous viral proteinases. | retroviral proteinase(pr)-catalyzed cleavage of the viral gag and gag-pol polyproteins within the nascent virus particle is required for productive viral infection. kinetic characterization and specificity analyses have been reported for several retroviral pr using oligopeptide substrates. in this study, we performed a comparative analysis of pr from avian, bovine, simian and human retroviruses using polyproteins of human immunodeficiency virus (hiv) type 1 or avian leukosis virus as substrates. ... | 1995 | 7883003 |
| structure and expression of endogenous retroviral sequences in the permanent lmh chicken cell line. | from dna mapping data, four endogenous proviral loci have been observed in the chicken permanent cell line lmh. the locus corresponding to endogenous virus (ev) ev1 is present in duplicate whereas the locus corresponding to ev3 is present in one copy. the other loci are probably ev6 and a solitary long terminal repeat. a rna northern blot analysis revealed both ev3 and ev6 transcripts but no ev1 transcript was detected. using avian leukosis virus (alv)-based vectors, transcomplementing assays we ... | 1995 | 7899200 |
| art-ch: a vl30 in chickens? | the complete sequence of art-ch, a recently found chicken retrotransposon (a. v. gudkov, e. a. komarova, m. a. nikiforov, and t. e. zaitsevskaya, j. virol. 66:1726-1736, 1992), was characterized. art-ch has the structure of a 3,300-bp-long provirus, including two 388-bp long terminal repeats (ltrs) (u3, 245 bp; r region, 17 bp; and u5, 126 bp), a trna(trp)-binding site, and a polypurine tract, similar to avian leukosis viruses. at least some of the approximately 50 genomic copies of art-ch are t ... | 1994 | 7904657 |
| distribution of targets for avian retrovirus dna integration in vivo. | the targeting of dna integration in retrovirus-infected cells is a central yet very poorly understood aspect of the biology of the virus. to investigate this problem, we have assessed the use of specific sites for integration targets of avian leukosis virus (alv) dna within defined regions of turkey embryo fibroblast (tef) cellular dna. for this purpose, we developed an assay of sufficient sensitivity and specificity to allow detection and location of single integration events in a population of ... | 1994 | 7926746 |
| a system for tissue-specific gene targeting: transgenic mice susceptible to subgroup a avian leukosis virus-based retroviral vectors. | avian leukosis viruses (alvs) have been used extensively as genetic vectors in avian systems, but their utility in mammals or mammalian cell lines is compromised by inefficient viral entry. we have overcome this limitation by generating transgenic mice that express the receptor for the subgroup a alv under the control of the chicken alpha sk-actin promoter. the skeletal muscles of these transgenic animals are susceptible to efficient infection by subgroup a alv. because infection is restricted t ... | 1994 | 7972042 |
| replication of an osteopetrosis-inducing avian leukosis virus in fibroblasts, osteoblasts, and osteopetrotic bone. | avian leukosis virus (alv)-induced osteopetrosis is caused by the abnormal growth and differentiation of osteoblasts. to evaluate the role of infection in osteopetrosis induction, the replication of an osteopetrosis-inducing virus (br21) has been compared in osteopetrotic bone, calvarial-derived osteoblasts, and chick embryo fibroblasts. much higher levels of infection occurred in diseased bone than in the cultures. severe cases of osteopetrosis contained 10 times more viral dna, 30 times more m ... | 1994 | 7975214 |
| establishment of interference in osteoblasts by an osteopetrosis-inducing avian leukosis virus. | avian leukosis virus (alv)-induced osteopetrosis is characterized by the presence of unintegrated viral dna is diseased bone. to learn more about this phenomenon, alvs with high (br21) and low (rav-1) osteopetrotic potential have been compared for the ability to establish superinfection resistance in cultures of calvarial-derived osteoblasts. both viruses could establish interference in osteoblast cultures that were maintained as growing cells. this interference was maintained when cultures were ... | 1994 | 7975235 |
| integration of multiple chicken retroviruses into multiple chicken herpesviruses: herpesviral gd as a common target of integration. | integration of two different avian retroviruses, reticuloendotheliosis virus (rev) and avian leukosis virus (alv), into the genome of two different avian herpesviruses, the herpesvirus of turkeys (hvt) and marek's disease virus (mdv), was investigated. integration events occurred by the fourth and sixth in vitro passage of cells coinfected with rev/hvt and alv/mdv, respectively. in order to further characterize the integration events, integrated proviruses and surrounding herpesviral genetic mat ... | 1994 | 8030268 |
| characterization of a molecular clone of a highly infectious avian leukosis virus. | a highly infectious avian leukosis virus (alv) has been molecularly cloned in a lambda phage and sequenced. in order to manipulate the genome of this alv and characterize the genetic determinants responsible for the high infectivity phenotype, a recombinant plasmid dna with the two ltr provirus was constructed. upon transfection of avian cells with this alv dna construct infectious viruses were produced as soon as 4 h after transfection and virus titer was 10(5) iu/ml after 24 h while that of th ... | 1993 | 8044699 |
| patterns of integration and expression of retroviral, non-replicative vectors in avian embryos: embryo developmental stage and virus subgroup envelope modulate tissue-tropism. | we previously demonstrated that avian leukemia viruses (alv) carrying the v-myc gene specifically induce two types of tumors, cardiomyocytic tumors when the virus is injected before embryonic day 3 (e3), skin tumors when the virus is injected at e3 or e5. aiming to elucidate the mechanisms which determine this time-dependent change in target, we infected chick and quail embryos at e3 and e5 with replication-deficient, lacz gene-carrying, alv-based viruses produced by a packaging cell line. three ... | 1993 | 8081875 |
| significance of t cell apoptosis for macrophages in hiv infection. | apoptosis is a major form of cell death in hiv infection. this review presents current ideas on the role of apoptosis in the development of aids. hiv may cause apoptosis either directly in individual cd4+ t cells through cellular infection and through the release of gp120 envelope protein, or indirectly by initiating systemic disturbances in the immune system. furthermore, although apoptosis is often assumed to be a biological dead end, linear, unintegrated retroviral dna survives apoptosis in a ... | 1994 | 8083597 |
| the vbp and a1/ebp leucine zipper factors bind overlapping subsets of avian retroviral long terminal repeat ccaat/enhancer elements. | two long terminal repeat (ltr) enhancer-binding proteins which may regulate high rates of avian leukosis virus (alv) ltr-enhanced c-myc transcription during bursal lymphomagenesis have been identified (a. ruddell, m. linial, and m. groudine, mol. cell. biol. 9:5660-5668, 1989). the genes encoding the a1/ebp and a3/ebp binding factors were cloned by expression screening of a lambda gt11 cdna library from chicken bursal lymphoma cells. the a1/ebp cdna encodes a novel leucine zipper transcription f ... | 1994 | 8083963 |
| gene conversion in the chicken immunoglobulin locus: a paradigm of homologous recombination in higher eukaryotes. | gene conversion was first defined in yeast as a type of homologous recombination in which the donor sequence does not change. in chicken b cells, gene conversion builds the antigen receptor repertoire by introducing sequence diversity into the immunoglobulin genes. immunoglobulin gene conversion continues at high frequency in an avian leukosis virus induced chicken b cell line. this cell line can be modified by homologous integration of transfected dna constructs offering a model system for stud ... | 1994 | 8143801 |
| transcriptional regulation of alv bursal lymphomagenesis. | avian leukosis virus (alv) induces bursal lymphoma in chickens after rare integration of proviral long terminal repeat (ltr) sequences next to the c-myc proto-oncogene. labile ltr-binding proteins are essential for c-myc hyperexpression, since ltr-enhanced transcription, as well as the activity of the ltr-binding proteins, is specifically decreased following protein synthesis inhibition. this lability is restricted to hematopoetic cells of alv-susceptible chicken strains, suggesting that the lab ... | 1994 | 8152295 |
| male-mediated venereal transmission of endogenous avian leukosis virus. | congenital transmission of avian leukosis viruses (alv) occurs readily through the egg, but transmission of alv through male seminal fluid is considered to be nonexistent or rare. progeny from mating endogenous late-feathering (lf), k/k+ males carrying an endogenous virus gene (ev21) with virgin early-feathering (ef) k+/w females were examined for the presence of infectious endogenous virus ev21 using an enzyme-labeled immunoassay for viral capsid antigen p27. all 177 lf chicks expressed ev21, p ... | 1994 | 8202427 |
| modifications in the binding domain of avian retrovirus envelope protein to redirect the host range of retroviral vectors. | on the basis of theoretical structural and comparative studies of various avian leukosis virus su (surface) envelope proteins, we have identified four small regions (i, ii, iii, and iv) in their receptor-binding domains that could potentially be involved in binding to receptors. from the envelope gene of an avian leukosis virus of subgroup a, we have constructed a set of su mutants in which these regions were replaced by the coding sequence of fla16, a 16-amino-acid rgd-containing peptide known ... | 1994 | 8207835 |
| importance of 3' non-coding sequences for efficient retrovirus-mediated gene transfer in avian cells revealed by self-inactivating vectors. | avian leukosis virus-derived vectors were constructed with an internal transcriptional promoter and various 3' non-coding sequences. deletions were introduced into the downstream u3 long terminal repeat (ltr) to obtain self-inactivation of ltr-mediated transcription after one round of replication. however, 3' non-coding sequences appeared to determine not only self-inactivation of the vectors but also gene transfer efficiency. further analysis revealed the influence of these sequences on both in ... | 1993 | 8380836 |
| functional and defective components of avian endogenous virus long terminal repeat enhancer sequences. | oncogenic avian retroviruses, such as rous sarcoma virus (rsv) and the avian leukosis viruses, contain a strong enhancer in the u3 portion of the proviral long terminal repeat (ltr). the ltrs of a second class of avian retroviruses, the endogenous viruses (ev) lack detectable enhancer activity. by creating ev-rsv hybrid ltrs, we previously demonstrated that, despite the lack of independent enhancer activity in the ev u3 region, ev ltrs contain sequences that are able to functionally replace esse ... | 1993 | 8382309 |
| use of helper cells with two host ranges to generate high-titer retroviral vectors. | we have recently described avian leukosis virus (alv)-based packaging cell lines that can produce helper-free alv-based retrovirus vectors with a, b, c, and e envelope host ranges. here, we report that lacz retroviral vectors of subgroup c or e can infect helper cells of subgroup a (isolde) which are then able to produce high titers of lacz recombinant viruses of subgroup a. superinfection of helper cells by lacz recombinant virus was performed by cocultivating packaging cells with two subgroup ... | 1993 | 8382402 |
| tissue tropism of avian leukosis viruses: analyses for viral dna and proteins. | analyses of six tissues from rous-associated virus type 1-infected chickens have revealed a number of tissue-specific differences in virus synthesis and distribution. chicks were infected at 1 day of age. tissue (bursa, thymus, liver, kidney, muscle, and brain) were harvested 1 month later. each of the tissues contained an average of 1.8 to 4 copies of viral dna per cell. most of this dna was integrated. in brain, about one-third of the total viral dna was in an unintegrated, linear form. bursa, ... | 1993 | 8382407 |
| synergism between the endogenous viral loci ev6 and ev9 in inducing immunological tolerance to avian leukosis virus. | 1. the course of infection by exogenous avian leukosis virus was followed in a commercial strain of white leghorn domestic fowls by measuring viral antigen in feather pulp and egg albumin. ten days after hatching, 2 out of 360 birds tested positive and at 286 days of age about 60% of the birds had been antigen positive at least once. 2. among the antigen positive birds, two groups could be distinguished: those which permanently and those which transiently expressed viral antigen. permanent antig ... | 1993 | 8385543 |
| consistent chromosomal aberration in cell lines transformed with marek's disease herpesvirus: evidence of genomic dna amplification. | a specific chromosomal aberration was observed in 14 of 15 avian lymphoblastoid cell lines transformed with marek's disease herpesvirus. this aberration, designated dup(1p)(p22-p23), appeared as an extra g-positive band and interband on the short arm of one chromosome i homolog. using fluorescent in situ hybridization, we identified amplified genomic dna sequences in this region. this amplification involves sequences linked to an endogenous retrovirus locus and genes in the histone multigene fam ... | 1993 | 8390410 |
| recovery of acutely transforming viruses from myeloid leukosis induced by the hprs-103 strain of avian leukosis virus. | viruses rapidly able to transform cultured chicken bone marrow cells have been isolated from cases of myelocytic myeloid leukosis (mml) induced experimentally by the hprs-103 strain of avian leukosis virus, and from field cases of mml. hprs-103 virus itself did not acutely transform cultured bone-marrow cells. these findings suggest that during myeloid leukemogenesis by hprs-103 virus, recombinant viruses are generated with transduced cellular oncogenes. the transformed cell appeared to be a mac ... | 1993 | 8395801 |
| research note: a rapid method for the detection of the rous-associated endogenous solitary long terminal repeat, ev15. | a rapid method has been developed for the detection of the solitary long terminal repeat ev15, a member of the avian leukosis virus (alv) family of endogenous viral elements (ev genes) in chickens. detection is accomplished by a polymerase chain reaction (pcr) assay that can be performed on purified genomic dna samples or crude preparations of partially purified whole blood lysates. the test discriminates unambiguously between birds that are homozygous ev15-, homozygous ev15+, or heterozygous ev ... | 1993 | 8397393 |
| identification of efiv, a stable factor present in many avian cell types that transactivates sequences in the 5' portion of the rous sarcoma virus long terminal repeat enhancer. | we define a protein complex present in avian nuclear extracts that interacts with the schmidt-ruppin strain of the rous sarcoma virus (rsv) long terminal repeat (ltr) between positions -197 and -168 relative to the transcriptional start site. we call this complex efiv and demonstrate that the efiv protein(s) is present in several avian cell types examined, including b cells (s13 and dt40), t cells (msb), and chicken embryo fibroblasts. we also report that the efiv binding site activates transcri ... | 1996 | 8523553 |
| production of avian leukosis virus particles in mammalian cells can be mediated by the interaction of the human immunodeficiency virus protein rev and the rev-responsive element. | in human immunodeficiency virus type 1-infected cells, the efficient expression of viral proteins from unspliced and singly spliced rnas is dependent on two factors: the presence in the cell of the viral protein rev and the presence in the viral rna of the rev-responsive element (rre). we show here that the hiv-1 rev/rre system can increase the expression of avian leukosis virus (alv) structural proteins in mammalian cells (d-17 canine osteosarcoma) and promote the release of mature alv virions ... | 1995 | 8524879 |
| a recombinant fowlpox virus expressing the envelope antigen of subgroup a avian leukosis/sarcoma virus. | a recombinant fowlpox virus (fpv) was constructed by inserting cloned sequences from schmidt-ruppin subgroup a avian sarcoma virus coding for the viral envelope (env) antigen into a nonessential region of fpv dna downstream from a synthetic promoter. sera from chickens hyperimmunized with the recombinant fpv neutralized the infectivity of the homologous subgroup a virus (rcasbp/ap) but only weakly neutralized the infectivity of rous sarcoma virus, another subgroup a avian leukosis virus. similar ... | 1995 | 8561735 |
| genomic analysis of collagen and endogenous virus loci in the ucd-200 and 206 lines of chickens, animal models for scleroderma. | university of california at davis (ucd) lines 200 and 206 chickens develop a hereditary systemic scleroderma-like connective tissue disease characterized by severe lymphocytic infiltration and excessive accumulation of collagen in skin and internal organs. the immune system seems to play an important role in the development and/or perpetuation of this condition. the main goal of our work with this strain is the investigation of interactions between endothelial cells, lymphocytes, macrophages and ... | 1995 | 8579730 |
| amino acid investigations of tumor-associated antigen of mc31 transformed cells. | there are numerous evidences (mainly indirect) for the presence of tumor-associated surface antigens (tasa) in cells transformed by avian oncornaviruses. hayami, et al. (1977) and ignjatovic et al. (1978) established that such antigens on avian leukosis virus (alv) cells have neither virus, nor oncofetal origin. on leukosis virus strain mc31-transformed turkey cells, filchev and ivanov (1986) and wesselinova (1989, 1991) also describe a tasa. but there are only a few studies on the nature and pr ... | 1995 | 8590434 |
| activation of homologous complement via the alternative complement pathway by quail cells transformed by rous sarcoma virus. | after incubation of the cells with fresh quail serum, deposition of the third component of complement (c3) was demonstrated on the cell surface of various quail cell lines transformed by rous sarcoma virus (rsv) as well as on that of primary quail embryo (qe) cells transformed by rsv. the c3 deposition occurred irrespective of virus production. on the other hand, the c-3 deposition was not observed on two quail cell lines transformed by a chemical carcinogen, qe cells infected with avian leukosi ... | 1995 | 8593301 |
| regulation of avian leukosis virus long terminal repeat-enhanced transcription by c/ebp-rel interactions. | the avian leukosis and sarcoma virus long terminal repeat (ltr) enhancers feature directly repeated ccaat/enhancer element sequences which are also found in many viral and cellular gene enhancers. while most members of the ccaat/enhancer element-binding protein (c/ebp) transcription factor family exhibit tissue-restricted expression, there may be ubiquitously expressed c/ebp-like factors that regulate widespread ccaat/enhancer element-driven transcription. an avian c/ebp-related factor designate ... | 1996 | 8627783 |
| expression of transduced genes in mice generated by infecting blastocysts with avian leukosis virus-based retroviral vectors. | transgenic mouse lines have been developed that express the tv-a receptor under the control of the chicken beta-actin promoter. these mice express the tv-a receptor in most or all tissues and in the early embryo. an avian leukosis virus (alv)-based retroviral vector system was used for the efficient delivery of genes into preimplantation mouse embryos from these transgenic lines. experimental animals could be generated quickly and easily by infecting susceptible blastocysts with alv-based retrov ... | 1996 | 8643506 |
| effect of serotype 2 and 3 marek's disease vaccines on the development of avian leukosis virus-induced pre-neoplastic bursal follicles. | the effect of serotype 2 and 3 marek's disease virus (mdv) vaccines on the development of pre-neoplastic bursal lesions induced by two strains of subgroup a avian leukosis virus (alv) was studied. chickens of line 15i5 x 7(1) susceptible to alv-induced lymphoma were inoculated at hatch with rous-associated virus-1 (rav-1) or strain rpl-40 of subgroup a alv. all chickens, except for negative controls, were also inoculated at hatch with strain 301b/1 of serotype 2 mdv or strain fc126 of turkey her ... | 1995 | 8719208 |
| activation of complement in quails bearing rous sarcoma virus-induced tumors. | the concentration of serum c3 in quails bearing tumors induced by rous sarcoma virus (rsv) was elevated in parallel with tumor growth, whereas serum c3 levels in quails inoculated with avian leukosis virus, which lacks transforming activity, showed a pattern similar to that in mock-infected quails. c3 deposition was also observed in almost all tumor cells at the tumor developing stage. these findings obtained in vivo suggest that the cells transformed by rsv activated the c3 on their surfaces. | 1995 | 8720051 |
| occupational exposure to poultry and prevalence of antibodies against marek's disease virus and avian leukosis retroviruses. | to compare the prevalence of antibodies against marek's disease herpes virus (mdv) and against avian leukosis viruses type c (alv) in groups of workers exposed to poultry and in unexposed groups. | 1996 | 8758036 |
| homologous and nonhomologous retroviral recombinations are both involved in the transfer by infectious particles of defective avian leukosis virus-derived transcomplementing genomes. | we previously described avian leukosis virus-based packaging cell lines that produce stocks of retroviral vectors in which replication-competent viruses were not detectable. however, following infection of target cells with these retroviral stocks, we recently obtained colonies resulting from the transmission of recombinant genomes. here, we have analyzed their genetic structure and shown that (i) each of them results from recombination between the packaging- and integration-defective transcompl ... | 1996 | 8764082 |
| infectious agents and environmental factors in lymphoid malignancies. | a strong association was found to exist between patterns of lymphoid malignancies and socioeconomic status. b-cell lymphomas and t-acute lymphoblastic leukemia are much more prevalent in developing countries where the chances of acquiring infections especially at a younger age are high. b-cell precursor acute lymphatic leukemia, however, are much more prevalent in the western world. many infectious agents are associated with lymphatic malignancies. epstein-barr virus is involved in african burki ... | 1996 | 8813340 |
| intratesticular inoculation of avian leukosis virus (alv) in chickens--production of neutralizing antibodies and lack of virus shedding into semen. | in order to investigate the possibility of producing transgenic chickens by injection of avian leukosis virus-based vectors into testis, we have analyzed the infection rate of testicular cells following inoculation of rous-associated virus type 1 (rav-1) into the gonads of adult and 1-wk-old brown leghorn males. viroproduction, neutralizing antibody production, and vital dna presence in testis, blood, muscle, and semen were analyzed at various times after infection. inoculation of rav-1 into the ... | 1996 | 8980816 |
| frequent detection of reviraemia in ducks persistently infected with avian leukosis retroviruses. | ducks intraembryonally infected with avian leukosis viruses of subgroup c (alv-c) were followed for a long period (up to 6.8 years), and the viraemia and production of virus-neutralizing antibodies were measured. in three independent experiments comprising ducks inoculated with uncloned and/or molecularly cloned alv-c, we found that after the elimination of primary post-hatching viraemia, reviraemia could be detected in 60-70% of infected animals. based on the course of viraemia, the individual ... | 1996 | 8997643 |
| bic, a novel gene activated by proviral insertions in avian leukosis virus-induced lymphomas, is likely to function through its noncoding rna. | the bic locus is a common retroviral integration site in avian leukosis virus (alv)-induced b-cell lymphomas originally identified by infection of chickens with alvs of two different subgroups (clurman and hayward, mol. cell. biol. 9:2657-2664, 1989). based on its frequent association with c-myc activation and its preferential activation in metastatic tumors, the bic locus is thought to harbor a gene that can collaborate with c-myc in lymphomagenesis and presumably plays a role in late stages of ... | 1997 | 9032277 |
| tissue tropism of the hprs-103 strain of j subgroup avian leukosis virus and of a derivative acutely transforming virus. | the tissue tropism was studied for the hprs-103 strain of avian leukosis virus, which belongs to a new envelope subgroup, designated j. studies were conducted in blood monocyte and bone marrow cell cultures and in chickens from six lines that had been shown previously to differ in susceptibility to induction by this virus of myeloid leukosis and other tumors. using an immunohistochemical technique to detect expression of viral group-specific antigen (gag) in various tissues, we detected no major ... | 1997 | 9066079 |
| avian retroviruses. | avian leukosis virus (alv) and reticuloendotheliosis virus (rev) are the most common naturally occurring avian retroviruses associated with neoplastic disease conditions in domesticated poultry. avian leukosis virus infects primarily chickens, whereas rev infects chickens, turkeys, and other avian species. in addition to causing tumors, both alv and rev can reduce productivity and induce immunosuppression and other production problems in affected flocks. | 1997 | 9071747 |
| the avian c/ebpgamma gene encodes a highly conserved leucine zipper transcription factor. | the c/ebp family of transcription factors regulates viral and cellular ccaat/enhancer element-mediated transcription. we report the isolation and characterization of genomic and cdna clones encoding avian ccaat/enhancer-binding protein-gamma (c/ebp gamma). a partial cdna clone for a c/ebp-related gene was previously identified by expression library screening for proteins binding the a1 ccaat/enhancer motif from the avian leukosis virus long terminal repeat [w. bowers and a. ruddell (1992) j. vir ... | 1997 | 9197547 |
| role of contact and genetic transmission of endogenous virus-21 in the susceptibility of chickens to avian leukosis virus infection and tumors. | the role of contact and genetic transmission of endogenous virus-21 (ev21) on response of chickens to avian leukosis virus (alv) infection and tumors was studied. f1 progeny of a cross between rprl late-feathering (lf) line ev21+ males and rprl early feathering (ef) line 15b1 females harboring or lacking ev21 were used. the ef chicks lacking ev21 were inoculated with a field strain of subgroup a alv at hatch and contact exposed to lf, ev21+ hatchmates for various time intervals. in a second expe ... | 1997 | 9200232 |
| recombinant env-gp85 of hprs-103 (subgroup j) avian leukosis virus: antigenic characteristics and usefulness as a diagnostic reagent. | we describe the construction of a recombinant baculovirus containing the cloned dna encoding the gp85 envelope glycoprotein of hprs-103 (subgroup j) avian leukosis virus fused to the carboxy-terminus of the affinity tag glutathione-s-transferase. the fusion protein was efficiently secreted into the supernatant medium of the infected insect cell culture and could be purified in a single step using immobilized glutathione. an enzyme-linked immunosorbent assay using the recombinant protein was foun ... | 1997 | 9201389 |
| rapid induction of b-cell lymphomas by avian leukosis virus. | avian leukosis viruses (alvs) that induce rapid b-cell lymphomas integrate into the c-myb gene and produce an alv-myb read-through rna, which is spliced to produce a truncated myb protein. the genetic determinants of such recombinant alvs have been mapped to a 42-nt deletion within the gag gene. this deletion increases splicing efficiency since it is located within a negative regulator of splicing. we propose that the deletion leads to increased production of myb protein by increasing splicing o ... | 1997 | 9209336 |
| use of reverse transcriptase polymerase chain reaction for detection of vaccine contamination by avian leukosis virus. | a reverse transcriptase polymerase chain reaction (rt-pcr) for avian leukosis virus (alv) was developed for the detection of contamination of vaccines produced in embryonated eggs and cell cultures derived from chicken. alv is highly pathogenic and induces a wide spectrum of disease in infected animals. alv can be divided into five subgroups (a-e). the envelope glycoprotein (env gp85) is the main antigen determinant and responsible for subgroup classification. viral rna of all subgroups (a-e) wa ... | 1997 | 9220392 |
| vbp and rela regulate avian leukosis virus long terminal repeat-enhanced transcription in b cells. | the avian leukosis virus (alv) long terminal repeat (ltr) contains a compact transcription enhancer that is active in many cell types. a major feature of the enhancer is multiple ccaat/enhancer element motifs that could be important for the strong transcriptional activity of this unit. the contributions of the three ccaat/enhancer elements to ltr function were examined in b cells, as this cell type is targeted for alv tumor induction following integration of ltr sequences next to the c-myc proto ... | 1997 | 9223487 |
| insertion of tandem direct repeats consisting of avian leukosis virus ltr sequences into the inverted repeat region of marek's disease virus type 1 dna. | the bc-1 strain dna of marek's disease virus type 1 (mdv1) at high-passage in culture was found to contain tandem direct repeats of the complete long terminal repeat (ltr) sequence of avian leukosis virus rav0 strain as the repeat unit within the short inverted repeats of the mdv1 dna. since the attenuated bc-1 strain grows well in cultured cells, the insertion site for retroviral dna sequence within the short inverted repeat of mdv1 dna is not essential for viral growth in culture. | 1997 | 9237356 |
| homologous modification of human chromosomal genes in chicken b-cell x human microcell hybrids | chicken cell lines derived from avian leukosis virus-induced b-cell tumors are highly recombination-proficient. in these cells, homologous recombination between transfected dna sequences and the corresponding chromosomal alleles occurs at high frequency, and targeting efficiencies of 10-90% can be obtained. we previously described a chromosome shuttle approach in which these cells can be used to modify human chromosomal alleles at high efficiency. in this method, marked human chromosomes are tra ... | 1996 | 9245343 |
| minimal truncation of the c-myb gene product in rapid-onset b-cell lymphoma. | oncogenic activation of c-myb by insertional mutagenesis has been implicated in rapid-onset b-cell lymphomas induced by the nonacute avian leukosis virus eu-8. in these tumors, proviruses are integrated either upstream of the c-myb coding region or within the first intron of c-myb. tumors with either type of integration contained identical chimeric mrnas in which the viral 5' splice site was juxtaposed to the 3' splice site of c-myb exon 2 and myb exon 1 was eliminated. both classes of integrati ... | 1997 | 9261372 |
| genetic determinant of rapid-onset b-cell lymphoma by avian leukosis virus. | infection of 10 day-old chicken embryos with the recombinant avian leukosis virus (alv) eu-8 induces a high incidence of rapid-onset b-cell lymphoma by insertional activation of the c-myb gene. lr-9, a related alv with differences from eu-8 in the gag and pol genes, induces rapid-onset lymphoma at only a low incidence. to localize the viral determinant(s) responsible for this biologic difference, we constructed and tested a series of reciprocal chimeras between eu-8 and lr-9 alvs. the ability to ... | 1997 | 9261373 |
| placement of trna primer on the primer-binding site requires pol gene expression in avian but not murine retroviruses. | in an early step in the retroviral infectious process, reverse transcriptase copies the genomic rna of the virus into complementary minus-strand dna. the primer for this synthetic event is a molecule of cellular trna, which is annealed by its 3' 18 nucleotides to a region of the genomic rna termed the primer-binding site (pbs); the sequence of the pbs and hence the identity of the trna depend upon the retrovirus species. in addition to the primer trna, retrovirus particles contain a substantial ... | 1997 | 9261422 |
| viral diseases of the immune system and strategies to control infectious bursal disease by vaccination. | viral infections which are immunosuppressive can affect the economics of poultry production, often as a result of the chicken's increased susceptibility to secondary infections and sub-optimal response to vaccinations. the mechanism of this immunosuppression has been studied in detail for certain chicken viruses. the replicating virus can have both direct and indirect effects on the cells of the immune system. the special role of the bursa of fabricius, as a lympho-epithelial organ, will be ment ... | 1997 | 9276986 |
| avian tumor viruses: persistent and evolving pathogens. | most neoplasias of lymphoid and other hematopoietic cells in commercial poultry are caused by viruses which belong to one of four distinct groups. marek's disease virus (mdv) is an oncogenic herpesvirus. avian leukosis virus (alv), reticuloendotheliosis virus (rev) and lymphoproliferative disease virus (lpdv) are oncogenic retroviruses. each group is distinguished by nucleic acid type, molecular structure, antigenicity, epidemiology, host range and other characteristics. however, most of these v ... | 1997 | 9276987 |
| selection of an avian retrovirus mutant with extended receptor usage. | receptor recognition by avian retroviruses is thought to involve the interaction of two regions of the su protein, hr1 and hr2, with the host cell surface receptor. these regions exhibit considerable variation, concordant with differences in receptor usage among the many avian leukosis virus subgroups. we hypothesize that some retroviruses have altered receptor usage in response to selective pressures imposed by receptor polymorphisms in their hosts. to test this hypothesis, we passaged td-pr-rs ... | 1997 | 9311868 |
| identification of a cellular receptor for subgroup e avian leukosis virus. | genetic studies in chickens and receptor interference experiments have indicated that avian leukosis virus (alv)-e may utilize a cellular receptor related to the receptor for alv-b and alv-d. recently, we cloned car1, a tumor necrosis factor receptor (tnfr)-related protein, that serves as a cellular receptor for alv-b and alv-d. to determine whether the cellular receptor for alv-e is a car1-like protein, a cdna library was made from turkey embryo fibroblasts (tefs), which are susceptible to alv- ... | 1997 | 9326659 |
| some chickens which are viraemic with subgroup j avian leukosis virus have antibody-forming cells but no circulating antibody. | new immunoperoxidase-based assays for splenic igg -antibody-forming cells (afc) and serum igg-antibody were used to look for antibody to hprs-103 in meat-type birds. meat type birds are known to be less likely to produce neutralising antibody and to be less likely to clear virus from their serum than layer-type birds after infection at hatch. in this work all 12 of the brown leghorn layer-type birds and 5/12 of the line 21 meat-type birds had produced afc and serum antibody and had cleared serum ... | 1997 | 9368962 |
| basic fibroblast growth factor induces cell migration and proliferation after glia-specific gene transfer in mice. | basic fibroblast growth factor (bfgf) is overexpressed in most high-grade human gliomas, implying that it is involved in the pathogenesis of these tumors. to assess the biological effect of inappropriate production of bfgf in normal astrocytes, we developed a system for glia-specific gene transfer in transgenic mice. a transgene encoding the receptor for subgroup a avian leukosis virus and controlled by the astrocyte-specific glial fibrillary acidic protein promoter permits efficient glia-specif ... | 1998 | 9448312 |
| a low incidence of histiocytic sarcomatosis associated with infection of chickens with the hprs-103 strain of subgroup j avian leukosis virus. | ten cases of histiocytic proliferative lesions in meat-type chickens associated in low incidence with infection by subgroup j avian leukosis virus (alv) are described. six were field cases in adult chickens from naturally infected flocks and four were from younger birds from transmission experiments with hprs-103 alv or the related acutely transforming alv strains 17 and 879. the lesions were observed mostly in the spleen and in some cases in other organs. microscopically, the lesions were compr ... | 1997 | 9454931 |