| efficient insertion from an internal long terminal repeat (ltr)-ltr sequence on a reticuloendotheliosis virus vector is imprecise and cell specific. | to examine the fidelity and efficiency of integration from a covalently closed long terminal repeat (ltr)-ltr sequence in vivo, we isolated individual spleen necrosis virus proviruses that arose following infection of chicken embryo fibroblasts (cefs) and sequenced the provirus-cell dna junctions. some but not all cef preparations allowed efficient insertion from the internal sequence. moreover, in contrast to integration from the normal ends of the viral dna, which occurs with precision with re ... | 1993 | 8382311 |
| fowlpox virus recombinants expressing the envelope glycoprotein of an avian reticuloendotheliosis retrovirus induce neutralizing antibodies and reduce viremia in chickens. | eight stable fowlpox virus (fpv) recombinants which express the envelope glycoprotein of the spleen necrosis virus (snv) strain of reticuloendotheliosis virus (rev), an avian retrovirus, were constructed. these recombinants differ in the genomic location of the inserted genes, in the orientation of the insert relative to flanking viral sequences, and in the promoter used to drive expression of the env gene. of these variables, promoter strength seems to be the most crucial. the p7.5 promoter of ... | 1993 | 8388488 |
| alteration of location of dimer linkage sequence in retroviral rna: little effect on replication or homologous recombination. | retrovirus particles contain a dimer of retroviral genomic rna. a defined region of the retrovirus genome has previously been shown to be important for both dimerization and encapsidation. to study the importance of the position of this encapsidation and dimerization signal for retroviral replication and homologous recombination, we used a previously described spleen necrosis virus-based helper cell system. this system allows retroviral vectors with multiple genetic markers to be studied after a ... | 1993 | 8388494 |
| the matrix region is responsible for the differential ability of two retroviruses to function as helpers for vector propagation. | we have investigated the ability of two related reticuloendotheliosis viruses to propagate a spleen necrosis virus (snv) based retroviral vector in canine osticosarcoma (d17) cells. reticuloendotheliosis virus strain a (rev-a) consistently propagated the vector more efficiently than snv in cell culture. to identify the area of the viral genome responsible for the superior helper function of rev-a, we constructed chimeric viruses between snv and rev-a. analysis of helper function indicated that a ... | 1993 | 8421894 |
| efficient initiation and strand transfer of polypurine tract-primed plus-strand dna prevent strand transfer of internally initiated plus-strand dna. | a critical step in retroviral reverse transcription is the initiation of plus-strand dna synthesis at the polypurine tract (ppt) and strand transfer of the ppt-primed strong-stop dna to the 5' end of the viral dna. an attachment site (att) immediately 3' to the ppt is essential for proper integration of proviral dna into the host chromosome. plus-strand dna synthesis is discontinuous in many retroviruses, indicating that sequences upstream of the ppt are also used to initiate plus-strand dna syn ... | 1996 | 8627689 |
| mutational analysis of the envelope protein of spleen necrosis virus. | spleen necrosis virus (snv) is an amphotropic type c retrovirus originally isolated from a duck. the envelope protein is related to that of type d retroviruses, and snv appears to use the same receptor as do simian retroviruses. however, little is known about envelope-receptor interactions of snv. we constructed a series of envelope mutants to characterize the su peptide of snv. point mutations were introduced throughout su in regions that are conserved among all retroviruses belonging to the sa ... | 1996 | 8709226 |
| retroviral mutation rates and a-to-g hypermutations during different stages of retroviral replication. | retroviruses mutate at a high rate in vivo during viral replication. mutations may occur during proviral transcription by rna polymerase ii, during minus-strand dna synthesis (rna template) by viral reverse transcriptase, or during plus-strand dna synthesis (dna template) by reverse transcriptase. to determine the contributions of different stages of replication to the retroviral mutation rates, we developed a spleen necrosis virus-based in vivo system to selectively identify mutations occurring ... | 1996 | 8892879 |
| partial reconstitution of a replication-competent retrovirus in helper cells with partial overlaps between vector and helper cell genomes. | contamination of retroviral vector preparations with replication-competent retroviruses is a major safety concern in human gene therapy. these can arise by recombination between retroviral vectors and packaging cell sequences. recently, we constructed new packaging lines, derived from spleen necrosis virus (snv) that do not contain overlapping regions of homology between these two components (dsh134g and dsh29b cells). these cell lines were tested for the presence of recombination products and r ... | 1996 | 8919592 |
| toward highly efficient cell-type-specific gene transfer with retroviral vectors displaying single-chain antibodies. | recently, we constructed retroviral vector particles derived from spleen necrosis virus (snv) that display a single-chain antibody (sca) on the viral surface. by transient transfection protocols, we showed that such particles are competent for infection and cell type specific. efficient infection was dependent on the presence of wild-type envelope, although wild-type snv was not infectious on target cells (t.-h. t. chu and r. dornburg, j. virol. 69:2659-2663, 1995; t.-h. t. chu, i. martinez, w. ... | 1997 | 8985404 |
| utilization of nonhomologous minus-strand dna transfer to generate recombinant retroviruses. | during reverse transcription, minus-strand dna transfer connects the sequences located at the two ends of the viral rna to generate a long terminal repeat. it is thought that the homology in the repeat (r) regions located at the two ends of the viral rna sequences facilitate minus-strand dna transfer. in this report, the effects of diminished r-region homology on dna synthesis and virus titer were examined. a retrovirus vector, py31, was constructed to contain the 5' and 3' cis-acting elements f ... | 1997 | 9032388 |
| the antiretrovirus drug 3'-azido-3'-deoxythymidine increases the retrovirus mutation rate. | it was previously observed that the nucleoside analog 5-azacytidine increased the spleen necrosis virus (snv) mutation rate 13-fold in one cycle of retrovirus replication (v. k. pathak and h. m. temin, j. virol. 66:3093-3100, 1992). based on this observation, we hypothesized that nucleoside analogs used as antiviral drugs may also increase retrovirus mutation rates. we sought to determine if 3'-azido-3'-deoxythymidine (azt), the primary treatment for human immunodeficiency virus type 1 (hiv-1) i ... | 1997 | 9151812 |
| homologous recombination occurs in a distinct retroviral subpopulation and exhibits high negative interference. | homologous recombination and deletions occur during retroviral replication when reverse transcriptase switches templates. while recombination occurs solely by intermolecular template switching (between copackaged rnas), deletions can occur by an intermolecular or an intramolecular template switch (within the same rna). to directly compare the rates of intramolecular and intermolecular template switching, two spleen necrosis virus-based vectors were constructed. each vector contained a 110-bp dir ... | 1997 | 9223494 |
| psi- vectors: murine leukemia virus-based self-inactivating and self-activating retroviral vectors. | we have developed murine leukemia virus (mlv)-based self-inactivating and self-activating vectors to show that the previously demonstrated high-frequency direct repeat deletions are not unique to spleen necrosis virus (snv) or the neomycin drug resistance gene. retroviral vectors pkd-httk and pkd-htptk containing direct repeats composed of segments of the herpes simplex virus type 1 thymidine kinase (htk) gene were constructed; in pkd-htptk, the direct repeat flanked the mlv packaging signal. th ... | 1997 | 9223521 |
| rnas from genetically distinct retroviruses can copackage and exchange genetic information in vivo. | sequence analysis suggests that ancient recombination events may have occurred between genetically distinct retroviruses. an experimental system was utilized to explore the genetic interaction between different viruses. moloney murine sarcoma virus and spleen necrosis virus are type c retroviruses that belong to different subgenera. with vectors containing packaging signals from these two viruses, dna proviruses containing genetic information from both rnas can be generated. this is the first ex ... | 1997 | 9223525 |
| characterization of an internal ribosomal entry segment within the 5' leader of avian reticuloendotheliosis virus type a rna and development of novel mlv-rev-based retroviral vectors. | the murine leukemia virus (mlv)-related type c viruses constitute a major class of retroviruses that includes numerous endogenous and exogenous mammalian viruses and the related avian spleen necrosis virus (snv). the mlv-related viruses possess a long and multifunctional 5' untranslated leader involved in key steps of the viral life cycle--splicing, translation, rna dimerization, encapsidation, and reverse transcription. recent studies have shown that the 5' leader of friend murine leukemia viru ... | 1997 | 9382952 |
| retroviral recombination rates do not increase linearly with marker distance and are limited by the size of the recombining subpopulation. | recombination occurs at high frequencies in all examined retroviruses. the previously determined homologous recombination rate in one retroviral replication cycle is 4% for markers 1.0 kb apart in spleen necrosis virus (snv). this has often been used to suggest that approximately 30 to 40% of the replication-competent viruses with 7- to 10-kb genomes undergo recombination. these estimates were based on the untested assumption that a linear relationship exists between recombination rates and mark ... | 1998 | 9445018 |
| retroviral recombination is nonrandom and sequence dependent. | sequence variation plays a significant role in the pathogenesis and persistence of retroviral infections and is a major obstacle in the development of vaccines as well as therapies against lethal diseases caused by retroviruses. recombination is one means by which sequence variation is generated. however, the basic molecular mechanisms of recombination are not adequately understood. in the present study, a spleen necrosis virus (snv) recombination system was used to ask whether a known hot spot ... | 1998 | 9527932 |
| relative rates of retroviral reverse transcriptase template switching during rna- and dna-dependent dna synthesis. | retroviral reverse transcriptases (rts) frequently switch templates during dna synthesis, which can result in mutations and recombination. the relative rates of in vivo rt template switching during rna- and dna-dependent dna synthesis are unknown. to determine the relative rates of rt template switching during copying of rna and dna templates, we constructed spleen necrosis virus-based retroviral vectors containing a 400-bp direct repeat. the directly repeated sequences were upstream of the poly ... | 1998 | 9573292 |
| the first strand transfer during hiv-1 reverse transcription can occur either intramolecularly or intermolecularly. | reverse transcription is a complicated process that involves at least two cdna transfer reactions to produce a full-length copy dna of the retroviral rna genome. because one retrovirus particle contains two identical genomic rna molecules, the transfers can occur in an intramolecular or intermolecular manner. the mechanism of the first transfer step (minus-strand strong-stop cdna transfer) has been studied previously in detail in transduction experiments with spleen necrosis virus vectors contai ... | 1998 | 9601495 |
| nonreciprocal pseudotyping: murine leukemia virus proteins cannot efficiently package spleen necrosis virus-based vector rna. | it has been documented that spleen necrosis virus (snv) can package murine leukemia virus (mlv) rna efficiently and propagate mlv vectors to the same titers as it propagates snv-based vectors. although the snv packaging signal (e) and mlv packaging signal (psi) have little sequence homology, similar double-hairpin rna structures were predicted and supported by experimental evidence. to test whether snv rna can be packaged by mlv proteins, we modified an snv vector to be expressed in an mlv-based ... | 1998 | 9620995 |
| deoxyribonucleoside triphosphate pool imbalances in vivo are associated with an increased retroviral mutation rate. | deoxyribonucleoside triphosphate (dntp) pool imbalances are associated with an increase in the rate of misincorporation and hypermutation during in vitro reverse transcription reactions. however, the effects of in vivo dntp pool imbalances on the accuracy of reverse transcription are unknown. we sought to determine the effects of in vivo dntp pool imbalances on retroviral mutation rates and to test our hypothesis that 3'-azido-3'-deoxythymidine (azt) increases the retroviral mutation rates throu ... | 1998 | 9733832 |
| cell-type-specific gene transfer into human cells with retroviral vectors that display single-chain antibodies. | the successful application of human gene therapy protocols on a broad clinical basis will depend on the availability of in vivo cell-type-specific gene delivery systems. we have developed retroviral vector particles, derived from spleen necrosis virus (snv), that display the antigen binding site of an antibody on the viral surface. using retroviral vectors derived from snv that displayed single-chain antibodies (scas) directed against a carcinoembryonic antigen-cross-reacting cell surface protei ... | 1998 | 9811755 |
| the rd114/simian type d retrovirus receptor is a neutral amino acid transporter. | the rd114/simian type d retroviruses, which include the feline endogenous retrovirus rd114, all strains of simian immunosuppressive type d retroviruses, the avian reticuloendotheliosis group including spleen necrosis virus, and baboon endogenous virus, use a common cell-surface receptor for cell entry. we have used a retroviral cdna library approach, involving transfer and expression of cdnas from highly infectable hela cells to nonpermissive nih 3t3 mouse cells, to clone and identify this recep ... | 1999 | 10051606 |
| insertion of sequences into the 3' untranslated region of a replication-competent spleen necrosis virus vector disrupts env gene expression. | the genomes of all replication-competent retroviruses contain cis-acting elements that regulate gene expression. however, the identities of many of these elements remain to be characterized. inserting sequences into the 3' untranslated region of a replication-competent spleen necrosis virus (snv) vector disrupted its ability to replicate. inserts varying in sequences and sizes (0.4-kb to 1.6-kb) all resulted in this defect. genetic compensation experiments and immunostaining revealed that env ge ... | 1999 | 10076510 |
| the 5' rna terminus of spleen necrosis virus contains a novel posttranscriptional control element that facilitates human immunodeficiency virus rev/rre-independent gag production. | previous work has shown that spleen necrosis virus (snv) long terminal repeats (ltrs) are associated with rex/rex-responsive element-independent expression of bovine leukemia virus rna and supports the hypothesis that snv rna contains a cis-acting element that interacts with cellular rex-like proteins. to test this hypothesis, the human immunodeficiency virus type 1 (hiv) rev/rre-dependent gag gene was used as a reporter to analyze various snv sequences. gag enzyme-linked immunosorbent assay and ... | 1999 | 10233946 |
| the nucleocapsid domain is responsible for the ability of spleen necrosis virus (snv) gag polyprotein to package both snv and murine leukemia virus rna. | murine leukemia virus (mlv)-based vector rna can be packaged and propagated by the proteins of spleen necrosis virus (snv). we recently demonstrated that mlv proteins cannot support the replication of an snv-based vector; rna analysis revealed that mlv proteins cannot efficiently package snv-based vector rna. the domain in gag responsible for the specificity of rna packaging was identified using chimeric gag-pol expression constructs. a competitive packaging system was established by generating ... | 1999 | 10516024 |
| a genetically engineered spleen necrosis virus-derived retroviral vector that displays the hiv type 1 glycoprotein 120 envelope peptide. | we reported that snv-derived retroviral vectors, which display single-chain antibodies on the viral surface, enable cell type-specific gene delivery into various human cells. in particular, the snv cell type-specific gene delivery vector system appears to be well suited to transduce genes into cells of the human hematopoietic system (jiang et al., j. virol. 72:10148-10156, 1998). here, we report the construction of snv vector particles that display the complete gp120 surface unit of the envelope ... | 1999 | 10566890 |
| avian reticuloendotheliosis virus strain a and spleen necrosis virus do not infect human cells. | spleen necrosis virus (snv) and reticuloendotheliosis virus strain a (rev-a) belong to the family of reticuloendotheliosis viruses and are 90% sequence related. snv-derived retroviral vectors produced by the rev-a-based d17.2g packaging cell line were shown to infect human cells (h.-m. koo, a. m. c. brown, y. ron, and j. p. dougherty, j. virol. 65:4769-4776, 1991), while similar vectors produced by another snv-based packaging cell line, dsh134g, are not infectious in human cells (reviewed by r. ... | 2000 | 10590142 |
| in vivo cell type-specific gene delivery with retroviral vectors that display single chain antibodies. | cell type-specific gene delivery will be essential for in vivo gene therapy. our laboratory has previously developed retroviral vector particles, derived from spleen necrosis virus, snv, which display the antigen-binding site of an antibody on the viral surface. such particles infected only human cells in vitro, which expressed a receptor recognized by the antibody. to test cell type-specific gene delivery in vivo, a mouse model system has been developed. antibiotic resistant human target and no ... | 1999 | 10637449 |
| targeting human t cells by retroviral vectors displaying antibody domains selected from a phage display library. | to generate t cell-specific retroviral vectors an scfv phage display library derived from immunized mice was selected for binding to the human t cell line molt-4/8. the scfv cdnas recovered from the selected phages were transiently expressed as an n-terminal fusion of the spleen necrosis virus (snv) transmembrane protein (tm) subunit of the viral envelope protein (env) in the cell line dsh-cxl, which packages the beta-galactosidase gene into snv particles. screening of supernatants from about 15 ... | 2000 | 10680843 |
| spleen necrosis virus-derived c-type retroviral vectors for gene transfer to quiescent cells. | gene therapy applications of retroviral vectors derived from c-type retroviruses have been limited to introducing genes into dividing target cells. here, we report genetically engineered c-type retroviral vectors derived from spleen necrosis virus (snv), which are capable of infecting nondividing cells. this has been achieved by introducing a nuclear localization signal (nls) sequence into the matrix protein (ma) of snv by site-directed mutagenesis. this increased the efficiency of infecting non ... | 2000 | 10835599 |
| effect of the murine leukemia virus extended packaging signal on the rates and locations of retroviral recombination. | reverse transcriptase (rt) switches templates frequently during dna synthesis; the acceptor template can be the same rna (intramolecular) or the copackaged rna (intermolecular). previous results indicated that intramolecular template switching occurred far more frequently than intermolecular template switching. we hypothesized that intermolecular template-switching events (recombination) occurred at a lower efficiency because the copackaged rna was not accessible to the rt. to test our hypothesi ... | 2000 | 10888634 |
| the 5' rna terminus of spleen necrosis virus stimulates translation of nonviral mrna. | the ru5 region at the 5' rna terminus of spleen necrosis virus (snv) has been shown to facilitate expression of human immunodeficiency virus type 1 (hiv) unspliced rna independently of the rev-responsive element (rre) and rev. the snv sequences act as a distinct posttranscriptional control element to stimulate gag rna nuclear export and association with polyribosomes. here we sought to determine whether ru5 functions to neutralize the cis-acting inhibitory sequences (inss) in hiv rna that confer ... | 2000 | 10933721 |
| development of an rev-independent, minimal simian immunodeficiency virus-derived vector system. | lentiviral vectors are attractive candidates for gene therapy because of their ability to integrate into nondividing cells. to date, conventional hiv-1-based vectors can be produced at higher titers, but concerns regarding their safety for human use exist because of the possibility of recombination leading to production of infectious virions with pathogenic potential. development of lentivirus vectors based on nonhuman lentiviruses constitutes an active area of research. we described a novel hiv ... | 2001 | 11339901 |
| the r region found in the human foamy virus long terminal repeat is critical for both gag and pol protein expression. | it has been suggested that sequences located within the 5' noncoding region of human foamy virus (hfv) are critical for expression of the viral gag and pol structural proteins. here, we identify a discrete approximately 151-nucleotide sequence, located within the r region of the hfv long terminal repeat, that activates hfv gag and pol expression when present in the 5' noncoding region but that is inactive when inverted or when placed in the 3' noncoding region. sequences that are critical for th ... | 2001 | 11435560 |
| frequency of direct repeat deletion in a human immunodeficiency virus type 1 vector during reverse transcription in human cells. | retroviral genetic rearrangements can result from reverse transcriptase template switching. most published data suggest that errors such as base misincorporation occur at similar frequencies for hiv-1 and for simple retroviruses such as spleen necrosis virus (snv) and murine leukemia virus (mulv). however, previous reports have suggested that template switch-mediated recombination is much more frequent for hiv-1 than for simple retroviruses. in this report, direct repeat deletion vectors similar ... | 2001 | 11485415 |
| targeted gene transfer to lymphocytes using murine leukaemia virus vectors pseudotyped with spleen necrosis virus envelope proteins. | in contrast to murine leukaemia virus (mlv)-derived vector systems, vector particles derived from the avian spleen necrosis virus (snv) have been successfully targeted to subsets of human cells by envelope modification with antibody fragments (scfv). however, an in vivo application of the snv vector system in gene transfer protocols is hampered by its lack of resistance against human complement. to overcome this limitation we established pseudotyping of mlv vector particles produced in human pac ... | 2001 | 11509952 |
| retroviral rna elements integrate components of post-transcriptional gene expression. | retroviruses vary widely in their ability to cause neoplastic transformation or immunodeficiency, and may even lack pathogenicity, but all retroviruses require cytoplasmic expression of intron-containing mrna. in the cytoplasm, the primary viral transcript has two essential roles as mrna template for protein synthesis and as genomic rna for packaging into progeny virions. cellular proteins are used by the virus to modulate synthesis, processing, and translation of the viral rna. to subvert the n ... | 2001 | 11720075 |
| improved retroviral packaging lines derived from spleen necrosis virus. | using highly efficient gene expression vectors, we constructed new retroviral packaging lines derived from spleen necrosis virus. core proteins are expressed from the murine leukemia virus promoter and enhancer followed by the tripartite leader sequence of an adenovirus. using different plasmids for envelope expression, we found that the efficiency of vector transduction is dependent on the level of gag-pol expression. the level of envelope expression did not have a measurable impact on vector v ... | 1995 | 11831705 |
| nuclear interactions are necessary for translational enhancement by spleen necrosis virus ru5. | the 5' long terminal repeat of spleen necrosis virus (snv) facilitates rev/rev-responsive element (rre)-independent expression of intron-containing human immunodeficiency virus type 1 (hiv-1) gag. the snv ru5 region, which corresponds to the 165-nucleotide 5' rna terminus, functions in a position- and orientation-dependent manner to enhance polysome association of intron-containing hiv-1 gag rna and also nonviral luc rna. evidence is mounting that association with nuclear factors during intron r ... | 2002 | 11884554 |
| cis-acting elements important for retroviral rna packaging specificity. | spleen necrosis virus (snv) proteins can package rna from distantly related murine leukemia virus (mlv), whereas mlv proteins cannot package snv rna efficiently. we used this nonreciprocal recognition to investigate regions of packaging signals that influence viral rna encapsidation specificity. although the mlv and snv packaging signals (psi and e, respectively) do not contain significant sequence homology, they both contain a pair of hairpins. this hairpin pair was previously proposed to be th ... | 2002 | 11967312 |
| identification of r-peptides in envelope proteins of c-type retroviruses. | activation of the murine leukaemia virus (mlv) envelope protein (env) requires proteolytic cleavage of the r-peptide, a 16 amino acid c-terminal part of the cytoplasmic tail (c-tail) of env. this paper demonstrates the presence of r-peptides in env proteins of c-type retroviruses of simian, avian and porcine origin. sequence alignment with the mlv c-tail led to the identification of a conserved hydrophobic protease cleavage motif located in the centre of retroviral env protein c-tails. expressio ... | 2002 | 12185279 |
| high fidelity of homologous retroviral recombination in cell culture. | genetic variation continues to be a major obstacle in the development of therapies and vaccines against retroviral infections and contributes extensively to viral pathogenesis and persistence. recombination is one mechanism that increases retroviral variation by shuffling mutations from different genomes. recent studies suggest that recombination not only shuffles the mutations but also generates them at high rates during reverse transcription. in contrast to these recent studies, this investiga ... | 2002 | 12209308 |
| ru5 of mason-pfizer monkey virus 5' long terminal repeat enhances cytoplasmic expression of human immunodeficiency virus type 1 gag-pol and nonviral reporter rna. | retroviruses utilize an unspliced version of their primary transcription product as an rna template for synthesis of viral gag and pol structural and enzymatic proteins. cytoplasmic expression of the gag-pol rna is achieved despite the lack of intron removal and the presence of a long and highly structured 5' untranslated region that inhibits efficient ribosome scanning. in this study, we have identified for the first time that the 5' long terminal repeat (ltr) of mason-pfizer monkey virus (mpmv ... | 2002 | 12239296 |
| functional replacement of nucleocapsid flanking regions by heterologous counterparts with divergent primary sequences: effects of chimeric nucleocapsid on the retroviral replication cycle. | nucleocapsid (nc) proteins in most retroviruses have a well-conserved cys-his box(es) as well as more divergent flanking regions that are rich in basic residues. mutations in the flanking regions can affect rna packaging, virus assembly, and reverse transcription of the viral rna. to gain a further understanding of the roles of nc flanking regions in the retroviral replication cycle, we generated and characterized chimeric gag-pol expression constructs derived from murine leukemia virus and sple ... | 2003 | 12477882 |
| displaying epidermal growth factor on spleen necrosis virus-derived targeting vectors. | targeted gene transfer into human cells has previously been achieved with spleen necrosis virus (snv)-derived vector particles harboring envelope (env) proteins which carry single chain fv (scfv) domains derived from antibodies. such cell targeting vectors have been found to directly transduce human cells expressing the cell surface molecules recognized by the respective scfv. in an attempt to achieve targeted gene transfer into epidermal growth factor receptor (egfr)-positive human cells, snv v ... | 2003 | 12504545 |
| the envelope glycoprotein of human endogenous retrovirus herv-w induces cellular resistance to spleen necrosis virus. | human endogenous retrovirus type w (herv-w) envelope glycoprotein (env) has recently been reported to induce fusion in cells expressing the rd-114 and type d retrovirus receptor (rdr) and to serve as a functional retroviral envelope protein. in this report, another biological function for herv-w was demonstrated by testing its ability to protect cells against retroviral infection. spleen necrosis virus (snv), a gammaretrovirus was chosen for testing resistance because it uses rdr to enter cells. ... | 2003 | 12664292 |
| reticuloendotheliosis viruses and derived vectors for human gene therapy. | the reticuloendotheliosis viruses (rev) spleen necrosis virus (snv) and reticuloendotheliosis virus strain-a (rev-a) are amphotropic retroviruses which infect a large variety of cells of avian and some mammalian species. they normally do not infect primate or rodent cells. however, they efficiently infect and integrate their genome into that of human cells when they are pseudotyped with the envelope protein of other mammalian retroviruses or the g protein of vesicular stomatitis virus (vsv) or r ... | 2003 | 12700113 |
| retroviral packaging cells encapsulated in theracyte immunoisolation devices enable long-term in vivo gene delivery. | the method of delivering a therapeutic gene into a patient is still one of the major obstacles towards successful human gene therapy. here we describe a novel gene delivery approach using theracyte immunoisolation devices. retroviral vector producing cells, derived from the avian retrovirus spleen necrosis virus, snv, were encapsulated in theracyte devices and tested for the release of retroviral vectors. in vitro experiments show that such devices release infectious retroviral vectors into the ... | 2003 | 12700116 |
| charged assembly helix motif in murine leukemia virus capsid: an important region for virus assembly and particle size determination. | we have identified a region near the c terminus of capsid (ca) of murine leukemia virus (mlv) that contains many charged residues. this motif is conserved in various lengths in most mlv-like viruses. one exception is that spleen necrosis virus (snv) does not contain a well-defined domain of charged residues. when 33 amino acids of the mlv motif were deleted to mimic snv ca, the resulting mutant produced drastically reduced amounts of virions and the virions were noninfectious. furthermore, these ... | 2003 | 12768025 |
| frequent dual initiation of reverse transcription in murine leukemia virus-based vectors containing two primer-binding sites. | retroviruses package two copies of viral rna into each virion. although each rna contains a primer-binding site for initiation of dna synthesis, it is unknown whether reverse transcription is initiated on both rnas. to determine whether a single virion is capable of initiating reverse transcription more than once, we constructed a murine leukemia virus-based vector containing a second primer-binding site (pbs) derived from spleen necrosis virus and inserted the green fluorescent protein gene (gf ... | 2003 | 12919734 |
| high rates of human immunodeficiency virus type 1 recombination: near-random segregation of markers one kilobase apart in one round of viral replication. | one of the genetic consequences of packaging two copies of full-length viral rna into a single retroviral virion is frequent recombination during reverse transcription. many of the currently circulating strains of human immunodeficiency virus type 1 (hiv-1) are recombinants. recombination can also accelerate the generation of multidrug-resistant hiv-1 and therefore presents challenges to effective antiviral therapy. in this study, we determined that hiv-1 recombination rates with markers 1.0, 1. ... | 2003 | 14512567 |
| cell-type-specific gene delivery into neuronal cells in vitro and in vivo. | the avian retroviruses reticuloendotheliosis virus strain a (rev-a) and spleen necrosis virus (snv) are not naturally infectious in human cells. however, rev-a-derived viral vectors efficiently infect human cells when they are pseudotyped with envelope proteins displaying targeting ligands specific for human cell-surface receptors. here we report that vectors containing the gag region of rev-a and pol of snv can be pseudotyped with the envelope protein of vesicular stomatitis virus (vsv) and the ... | 2003 | 14517061 |
| primary sequence and secondary structure motifs in spleen necrosis virus ru5 confer translational utilization of unspliced human immunodeficiency virus type 1 reporter rna. | the 5' long terminal repeat (ltr) of spleen necrosis virus (snv) contains a unique posttranscriptional control element that facilitates rev/rev-responsive element-independent expression of unspliced human immunodeficiency virus type 1 (hiv-1) gag reporter rna. hiv-1 gag expression is eliminated when snv ltr is repositioned to the 3' untranslated region or when the ru5 region is positioned in the antisense orientation. ru5 corresponds to the 5' rna terminus, and results presented here indicate th ... | 2003 | 14581534 |
| analysis of synergy between divergent simple retrovirus posttranscriptional control elements. | mason-pfizer monkey virus (mpmv) and spleen necrosis virus (snv) are simple retroviruses that encode functionally divergent cis-acting rna elements that use cellular proteins to facilitate nuclear export and translation of unspliced viral rna. we tested the hypothesis that a combination of mpmv constitutive transport element (cte) and snv or mpmv ru5 translational enhancer on unspliced hiv-1 gag-pol reporter rna synergistically augments gag production. results of transient transfection assays va ... | 2003 | 14675633 |
| spliced spleen necrosis virus vector rna is not encapsidated: implications for retroviral replication and vector design. | rna splicing is a complex event in the retroviral life cycle and can involve multiple steps, as well as cis-acting sequences, to maintain a proper balance of spliced and unspliced viral rna for translation and encapsidation. the retroviral rna can be processed by cellular machinery and enables the removal of intronic sequences. we aimed to utilize the removal of a synthetic intron for targeted gene expression. to analyze intron removal and gene expression, we have constructed a novel self-inacti ... | 2004 | 15093186 |
| cross-packaging of human immunodeficiency virus type 1 vector rna by spleen necrosis virus proteins: construction of a new generation of spleen necrosis virus-derived retroviral vectors. | the ability of the nonlentiviral retrovirus spleen necrosis virus (snv) to cross-package the genomic rna of the distantly related human immunodeficiency virus type 1 (hiv-1) and vice versa was analyzed. such a model may allow us to further study hiv-1 replication and pathogenesis, as well as to develop safe gene therapy vectors. our results suggest that snv can cross-package hiv-1 genomic rna but with lower efficiency than hiv-1 proteins. however, hiv-1-specific proteins were unable to cross-pac ... | 2004 | 15163741 |
| spleen necrosis virus-based vector delivery of anti-hiv-1 genes potently protects human hematopoietic cells from hiv-1 infection. | in this study, we report on the efficacy of using a spleen necrosis virus (snv)-based vector delivery system to block human immunodeficiency virus type i (hiv-1) replication in human hematopoietic cells. these efforts were directed towards the development of human immune system cell resistance to hiv-1 infection, based on the strategy of "intracellular immunization" via generation of a series of anti-hiv-1 therapeutic constructs carrying scfvs, single-chain variable fragments, against hiv-1 inte ... | 2005 | 15661158 |
| cooperative effect of gag proteins p12 and capsid during early events of murine leukemia virus replication. | the gag polyprotein of murine leukemia virus (mlv) is processed into matrix (ma), p12, capsid (ca), and nucleocapsid (nc) proteins. p12 affects early events of virus replication and contains a pppy motif important for virus release. to probe the functions of p12 in the early steps of mlv replication, we tested whether p12 can be replaced by spleen necrosis virus (snv) p18, human immunodeficiency virus type 1 p6, or rous sarcoma virus p2b. analyses revealed that all chimeras generated virions at ... | 2005 | 15767417 |
| human immunodeficiency virus type 1 nef potently induces apoptosis in primary human brain microvascular endothelial cells via the activation of caspases. | the lentiviral protein nef plays a major role in the pathogenesis of human immunodeficiency virus type i (hiv-1) infection. although the exact mechanisms of its actions are not fully understood, nef has been shown to be essential for the maintenance of high-titer viral replication and disease pathogenesis in in vivo models of simian immunodeficiency virus infection of monkeys. nef has also been suggested to play a pivotal role in the depletion of t cells by promoting apoptosis in bystander cells ... | 2005 | 15767427 |
| a nuclear localization signal in the matrix of spleen necrosis virus (snv) does not allow efficient gene transfer into quiescent cells with snv-derived vectors. | a major limitation in gene therapy for vectors derived from moloney murine leukemia virus (mlv) is that they only deliver genes into dividing cells. in this study, a careful comparison of spleen necrosis virus (snv)-derived vectors with mlv and human immunodeficiency virus (hiv)-1 retroviral vectors indicated that snv vectors can deliver genes 4-fold more efficiently than mlv vectors into aphidicolin-arrested cells, although at a 25-fold lower efficiency than hiv-1-derived vectors. furthermore, ... | 2005 | 15961134 |
| coordinate enhancement of transgene transcription and translation in a lentiviral vector. | coordinate enhancement of transgene transcription and translation would be a potent approach to significantly improve protein output in a broad array of viral vectors and nonviral expression systems. many vector transgenes are complementary dna (cdna). the lack of splicing can significantly reduce the efficiency of their translation. some retroviruses contain a 5' terminal post-transcriptional control element (pce) that facilitates translation of unspliced mrna. here we evaluated the potential f ... | 2006 | 16480517 |
| phylogenetic analyses indicate little variation among reticuloendotheliosis viruses infecting avian species, including the endangered attwater's prairie chicken. | reticuloendotheliosis virus infection, which typically causes systemic lymphomas and high mortality in the endangered attwater's prairie chicken, has been described as a major obstacle in repopulation efforts of captive breeding facilities in texas. although antigenic relationships among reticuloendotheliosis virus (rev) strains have been previously determined, phylogenetic relationships have not been reported. the pol and env of rev proviral dna from prairie chickens (pc-r92 and pc-2404), from ... | 2006 | 16497405 |
| envelope proteins of spleen necrosis virus form infectious human immunodeficiency virus type 1 pseudotype vector particles, but fail to incorporate upon substitution of the cytoplasmic domain with that of gibbon ape leukemia virus. | the wild-type (wt) envelope (env) proteins of spleen necrosis virus (snv), together with the transmembrane (tm) protein fused to antibody domains (scfv), have been used for the generation of stable packaging cell lines releasing pseudotyped cell targeting vectors derived from snv and murine leukemia virus (mlv). as a first step towards assessing whether hiv-1(snv/tm-scfv) packaging cells could be established for the production of lentiviral cell targeting vectors, it is reported here that infect ... | 2006 | 16690921 |
| survival of early preimplantation porcine embryos after co-culture with cells producing an avian retrovirus. | to determine the relative survival of porcine embryos after co-culture with cells producing an avian retrovirus, four-cell stage embryos were obtained from sows following synchronization with altrenogest and superovulation with gonadotropins. these embryos were randomly assigned to the following treatments: no manipulation (zona-intact); zona removed with acidified tyrode's solution (zona-free); and zona removed followed by co-culture with d-17 canine cells producing an avian retrovirus vector d ... | 1991 | 16726921 |
| high frequency of genetic recombination is a common feature of primate lentivirus replication. | recent studies indicate that human immunodeficiency virus type 1 (hiv-1) recombines at exceedingly high rates, approximately 1 order of magnitude more frequently than simple gammaretroviruses such as murine leukemia virus and spleen necrosis virus. we hypothesize that this high frequency of genetic recombination is a common feature of primate lentiviruses. alternatively, it is possible that hiv-1 is unique among primate lentiviruses in possessing high recombination rates. among other primate len ... | 2006 | 16973569 |
| full genome sequence and some biological properties of reticuloendotheliosis virus strain apc-566 isolated from endangered attwater's prairie chickens. | reticuloendotheliosis virus (rev) causes runting, high mortality, immunosuppression, and chronic neoplasia associated with t and/or b cell lymphomas in a variety of domestic and wild birds, including attwater's prairie chickens (apc) (tympanuchus cupido attwateri). the complete proviral sequence of a recent rev isolate from apc (rev apc-566) was determined. this virus was isolated from an apc maintained in captivity in a reproduction program intended to avoid its extinction. rev apc-566 was dete ... | 2007 | 17098316 |
| capsid is an important determinant for functional complementation of murine leukemia virus and spleen necrosis virus gag proteins. | in this report, we examined the abilities and requirements of heterologous gag proteins to functionally complement each other to support viral replication. two distantly related gammaretroviruses, murine leukemia virus (mlv) and spleen necrosis virus (snv), were used as a model system because snv proteins can support mlv vector replication. using chimeric or mutant gag proteins that could not efficiently support mlv vector replication, we determined that a homologous capsid (ca) domain was neces ... | 2007 | 17156810 |
| hiv-1 vpr potently induces programmed cell death in the cns in vivo. | the human immunodeficiency virus type i (hiv-1) accessory protein vpr has been associated with the induction of programmed cell death (apoptosis) and cell-cycle arrest. studies have shown the apoptotic effect of vpr on primary and established cell lines and on diverse tissues including the central nervous system (cns) in vitro. however, the relevance of the effect of vpr observed in vitro to hiv-1 neuropathogenesis in vivo, remains unknown. due to the narrow host range of hiv-1 infection, no ani ... | 2007 | 17328670 |
| rna helicase a interacts with divergent lymphotropic retroviruses and promotes translation of human t-cell leukemia virus type 1. | the 5' untranslated region (utr) of retroviruses contain structured replication motifs that impose barriers to efficient ribosome scanning. two rna structural motifs that facilitate efficient translation initiation despite a complex 5' utr are internal ribosome entry site (ires) and 5' proximal post-transcriptional control element (pce). here, stringent rna and protein analyses determined the 5' utr of spleen necrosis virus (snv), reticuloendotheliosis virus a (rev-a) and human t-cell leukemia v ... | 2007 | 17426138 |
| enhanced gene expression conferred by stepwise modification of a nonprimate lentiviral vector. | the practical application of gene transfer as a treatment for genetic diseases such as cystic fibrosis or hemophilia has been hindered, in part, by low efficiencies of vector delivery and transgene expression. we demonstrated that a feline immunodeficiency virus (fiv)-based lentiviral vector pseudotyped with the envelope glycoprotein from the baculovirus autographa californica (gp64) efficiently transduces and persistently expresses a reporter gene in respiratory epithelium in the absence of age ... | 2007 | 18052720 |
| use of the polymerase chain reaction for the diagnosis of natural infection of chickens and turkeys with marek's disease virus and reticuloendotheliosis virus. | marek's disease (md) is a highly contagious lymphoproliferative disease of chickens caused by a herpesvirus, while reticuloendotheliosis (rev) virus is an avian c-type retrovirus that causes bursal and nonbursal lymphomas which often closely resemble mdv lymphomas. to provide a rapid and sensitive means of diagnosing and differentiating between these two neoplastic conditions, we have applied the pcr. the primers chosen to detect mdv sequences flank the 132 bp tandem repeat of the bamhi-h fragme ... | 1995 | 18645767 |
| enhancement of reticuloendotheliosis virus-induced bursal lymphomas by serotype 2 marek's disease virus. | the effect of serotype 2 and 3 marek's disease virus (mdv) vaccines on the pathogenesis of reticuloendotheliosis virus (rev)-induced bursal and non-bursal lymphomas was examined in chickens of rprl lines 15i(5) x 7(1) and 6(3) x 0, respectively. at hatch, chickens were vaccinated with strain 301b/1 of serotype 2 mdv or strain fc126 of turkey herpesvirus (hvt), a serotype 3 mdv and inoculated with spleen necrosis virus (snv), a non-defective strain of rev. in another experiment, bursas from 14-we ... | 1996 | 18645839 |
| detection of reticuloendotheliosis virus infection using the polymerase chain reaction. | the polymerase chain reaction (pcr) was shown to be a sensitive and useful method for detection of infection by members of the group of avian reticuloendotheliosis virus (rev). genomic dna extracted from chick embryo fibroblasts (cefs), blood and tumours of chickens experimentally infected with the spleen necrosis virus (snv) strain of rev was used as the target for chain elongation. deoxyoligonucleotide primers that encompass a portion of the unique 3', repeat and unique 5' region of the long t ... | 1993 | 18671039 |
| murine retroviruses re-engineered for lineage tracing and expression of toxic genes in the developing chick embryo. | we describe two replication incompetent retroviral vectors that co-express green fluorescent protein (gfp) and beta-galactosidase. these vectors incorporate either the avian reticuloendotheliosis (spleen necrosis virus; snv) promoter or the chick beta-actin promoter, into the backbone of the murine leukemia (mlv) viral vector. the additional promoters drive transgene expression in avian tissue. the remainder of the vector is mlv-like, allowing high titer viral particle production by means of tra ... | 2008 | 18942139 |
| generation of retroviral particles for the spleen necrosis virus (snv)-based vector system and their use in transduction of various cell types. | genetically engineered retroviruses are widely used for gene delivery into human cells. a number of investigators have studied spleen necrosis virus (snv) as a vehicle for gene delivery. vectors developed from snv and its closely associated avian reticuloendotheliosis virus strain a (rev-a) can be used for gene transfer into a variety of cells, including primary hematopoietic cells and human brain and post-mitotic neuronal cells that are difficult to transduce with other vector systems. snv-base ... | 2010 | 20516173 |
| characterization of reticuloendotheliosis virus isolates obtained from broiler breeders, turkeys, and prairie chickens located in various geographical regions in the united states. | nine reticuloendotheliosis virus (rev) isolates obtained from broiler breeders, turkeys, and prairie chickens located in three different geographical regions in the usa, and three isolates obtained from known contaminated live-virus vaccines were characterized using polymerase chain reaction (pcr) and indirect immunofluorescence (ifa) assays. all isolates were propagated in chicken embryo fibroblasts obtained from a specific pathogen free breeder flock. pcr analysis of all 12 isolates resulted i ... | 2010 | 20954015 |
| in vivo diversification and migrations of chick embryo heart muscle cells: a morphometric analysis with alv- and snv-based non-replicative vectors. | by means of a reporter gene we previously demonstrated that non-replicative avian leukemia virus- and spleen necrosis virus-based retroviral vectors were preferentially expressed in the heart of avian embryos from different species. using a computer-assisted approach, we now compare clones tagged by the two types of vectors, for volume, anatomical and subanatomical localisation, number of hoechst-stained cell nuclei and mean cell division time during the period of heart morphogenesis, i.e. from ... | 1996 | 24173519 |
| heart targeting of retroviral expression in avian embryos: a species-independent phenomenon. | a replication-incompetent retroviral vector derived from spleen necrosis virus (snv), in which the viral structural genes gag, pol, and env were replaced with the bacterial β-galactosidase gene lacz, was used to infect embryos from outbred and inbred chicken lines, japanese quail and duck between embryonic day 0 and 13. lacz expression was restricted to a few organs or cell types, and this distribution was not influenced by the different routes of inoculation tested but was specified by the age ... | 1995 | 28305962 |
| molecular characterization and expression pattern of tumor suppressor protein p53 in mandarin fish, siniperca chuatsi following virus challenge. | in recent years, the tumor suppressor protein p53, which is crucial for cellular defense against tumor development, has also been implicated in host antiviral defense. in the present study, a 1555 bp full-length cdna of p53 from mandarin fish (siniperca chuatsi) (sc-p53) was cloned and characterized. quantitative real-time pcr assays revealed that sc-p53 was expressed in all tissues examined, and it was most abundant in the gill and kidney. recombinant sc-p53 fused with a his·tag was expressed i ... | 2016 | 26980610 |
| hiv-1 and two avian retroviral 5' untranslated regions bind orthologous human and chicken rna binding proteins. | essential host cofactors in retrovirus replication bind cis-acting sequences in the 5'untranslated region (utr). although host rbps are crucial to all aspects of virus biology, elucidating their roles in replication remains a challenge to the field. here rna affinity-coupled-proteomics generated a comprehensive, unbiased inventory of human and avian rna binding proteins (rbps) co-isolating with 5'utrs of hiv-1, spleen necrosis virus and rous sarcoma virus. applying stringent biochemical and stat ... | 2015 | 26584240 |
| [immunogenicity of co-expressed p30-gp90 against reticuloendotheliosis virus]. | to study the immunogenicity of co-expression of p30, one of a group specific antigens, and glycoprotein gp90 genes of reticuloendotheliosis virus (rev). | 2014 | 24984528 |
| autophagy promoted infectious kidney and spleen necrosis virus replication and decreased infectious virus yields in cpb cell line. | autophagy plays important functions in viral replication and pathogenesis. in this study, we investigated the role of autophagy in the replication of infectious kidney and spleen necrosis virus (isknv), an agent that has caused devastating losses in chinese perch (siniperca chuatsi) industry. we found that isknv infection triggered the complete autophagic process, as demonstrated by microtubule-associated protein 1 light chain 3b ii (lc3b-ii) conversion, an increased accumulation of punctate gfp ... | 2017 | 27856327 |
| transcriptional analysis of host responses related to immunity in chicken spleen tissues infected with reticuloendotheliosis virus strain snv. | in avian species, the reticuloendotheliosis virus (rev) causes severe immunosuppression and other symptoms, including avian dwarfing syndrome, and chronic tumors in lymphoid and other tissues. the pathogenesis of rev and its interaction with the host have yet to be fully elucidated with transcriptional studies on the changes in host gene expression after rev infection at the body level. in this study, the spleen necrosis virus (snv) was used to inoculate the one-day-old specific pathogen free (s ... | 2019 | 31228642 |
| integrated analysis of mirna and mrna expression profiles in spleen of specific pathogen-free chicken infected with avian reticuloendotheliosis virus strain snv. | the reticuloendotheliosis virus (rev) primarily causes avian severe immunosuppression, in addition to other symptoms, which include avian dwarfing syndrome and chronic tumors in lymphoid and other tissue. to date, rev's molecular mechanisms leading to immunosuppression have not been fully elucidated. in the current study, we aimed to elucidate the role of micrornas (mirna) in regulating gene expression during rev infections. therefore, we used a high-dose spleen necrosis virus (snv) model of rev ... | 2019 | 30818863 |