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[intercellular interactions in swine bone marrow cell culture and ppk-66b cell line infected with african swine fever virus]. 19969081441
classical swine fever virus-specific cytotoxic t lymphocytes and identification of a t cell epitope.classical swine fever virus (csfv)-specific cytotoxic t lymphocytes (ctl) were derived from peripheral blood mononuclear leukocytes of immunized nih-minipigs (mhc d/d haplotype) after in vitro restimulation with infectious csfv. their cytotoxic activity was determined against csfv-infected target cells obtained from simian virus 40 (sv40) large t antigen-transfected immortalized kidney cells of a syngeneic miniature swine. experiments with separated effector cell populations revealed that the cs ...19958847509
evolution of viral dna-dependent rna polymerases.the dna-dependent rna polymerase (ddrp or rnap) is an essential enzyme of transcription of replicating systems of prokaryotic and eukaryotic organisms as well as cytoplasmic dna viruses. ddrps are complex multisubunit enzymes consisting of 8-14 subunits, including two large subunits and several smaller polypeptides (small subunits). an extensive search between the amino acid sequences of the known largest subunit of dna-dependent rna polymerases (rpo1) of different organisms indicates that all t ...19958828152
experimental quantification of transmission of genetically engineered pseudorabies virus.there is concern that live pseudorabies virus (prv) vaccine or prv vector vaccine strains may spread from vaccinated to unvaccinated pigs. moreover, it is feared that recombining prv vaccine strains with related vaccine or wild-type strains may lead to spread and survival of recombinant prv. to learn more about to what extent different prv vaccine strains could spread we used a previously described experimental model to study the transmission of intranasally inoculated prv mutant strains under e ...19958701591
the african swine fever virus iap homolog is a late structural polypeptide.the analysis of the complete nucleotide sequence of the african swine fever virus genome has revealed the existence of a number of genes potentially capable of modifying the host's response to the virus infection. in this report, we describe the results of the characterization of the a224l gene that encodes a novel member of the family of apoptosis inhibitors known as iap proteins. a224l is expressed during the late phase of the infectious cycle, and its polypeptide product is assembled into vir ...19958553574
baculovirus expression and affinity purification of protein e2 of classical swine fever virus strain alfort/187.the genome region encoding the major envelope glycoprotein e2 (gp55) of the classical swine fever virus (csfv) strain alfort/187 was cloned and sequenced. the e2 gene, either with or without additional authentic 5'-terminal sequences coding for two variants of a putative signal sequence, was used to construct recombinant baculoviruses expressing the respective glycosylated and nonglycosylated e2 protein in insect cells. the signal sequences mediated glycosylation in insect cells, but no efficien ...19958560771
characterization of the hog cholera virus 5' terminus.hog cholera virus (hocv) 5' terminus of the ald and gpe(-) strains were analyzed by using rapid amplification of cdna end method (5'race). an additional nine nucleotides were found at the 5' termini of genomic rna in the ald and gpe(-) strains of hocv. these nine nucleotides were also conserved in bvdv and were suggested to form a hairpin structure at the 5' terminus by computer-assisted analysis. it seems possible that the secondary structure and/or the 5' terminus sequence has a significant ro ...19958560779
isolation of bovine viral diarrhea virus-like pestiviruses from roe deer (capreolus capreolus).cytopathogenic pestiviruses were isolated from two seronegative free-ranging roe deer (capreolus capreolus) from northern germany (schleswig-holstein): an adult female and a young buck collected on 6 december 1990 and 26 july 1991, respectively. the two isolates were identified by polymerase chain reaction as pestiviruses. however, they were negative when primers specific for bovine virus diarrhea virus or classical swine fever virus were used, indicating that the two isolates might belong to a ...19958583645
[diagnosis of contagious diseases in animals using pcr].the pcr is used for diagnostic purposes as it allows to detect infections agents within a much shorter time than by cultural isolation. in addition, it can detect non-infectious viruses and bacteria in clinical samples. these advantages are important factors in the diagnosis of highly contagious animal diseases (mainly caused by viruses) since a rapid laboratory diagnosis will allow to take immediate disease control actions. pcr is routinely used at the institute of african and classical swine f ...19958584867
classical swine fever in wild boar (sus scrofa)--experimental infections and viral persistence.a pregnant wild boar and two wild boar weaners were inoculated intranasally with a field isolate of classical swine fever virus (csfv) recently derived from a diseased domestic pig. the clinical, pathological and haematological findings noted in the young wild boars were comparable to those in domestic weaner pigs inoculated with the same virus isolate. both wild boars showed the acute haemorrhagic form of csf, one animal died 18 days post inoculation (p. i.) and the second one had to be euthani ...19958591736
a serological study on infection patterns, control and persistence of classical swine fever in infected farms in the philippines.in 3 farrow-to-finish farms with enzootic classical swine fever (csf) all sick pigs were culled and an intensive vaccination program was introduced. boars and cows were vaccinated every 6 months and piglets at the age of 6 and 8 weeks. the infection was monitored on clinical grounds and by means of serological examination of the farms. serological results reflected well the clinical situation in the farms. high titers and high percentage of animals with positive titers were observed in infected ...19958593302
serological study of pigs for antibody against african swine fever virus in two areas of southern malawi.a serological survey was conducted in july 1991 on domestic pigs in two areas of southern malawi which were severely affected by the african swine fever (asf) epizootic in 1989-1991. sixty-six of the 216 owners questioned reported having witnessed asf in their pigs. forty-seven owners had pigs with antibodies against asf virus, and the overall prevalence of pigs with anti-asf virus antibodies was found to be 12.4%, in 445 pigs sampled in 35 villages. spread of asf was thought to occur principall ...19958593400
evaluation of the enzyme-linked immunosorbent assay for the rapid screening and detection of classical swine fever virus antigens in the blood of pigs.a workshop was convened, at which seven enzyme-linked immunosorbent assays (elisas) were compared with virus isolation for the detection of viraemia in serial blood samples collected from six pigs at up to fourteen days after inoculation with classical swine fever virus. all elisas were of the double antibody sandwich type, using monoclonal and/or polyclonal antibodies to detect a variety of viral proteins in leukocytes, or in anti-coagulated blood or serum. compared to virus isolation, specific ...19958593401
reverse transcription combined with polymerase chain reaction as a detection method for pestiviral infections.an assay based on reverse transcription coupled with the polymerase chain reaction (rt-pcr) was used for the detection of hog cholera virus (hcv) and bovine virus diarrhoea virus (bvdv) in cell culture. in this study, a precipitate of the supernatants derived from cell cultures infected with hcv and bvdv was used in rt reactions, in place of extracted viral rna. both rt and pcr were performed using recombinant thermus thermophilus (rtth) dna polymerase. the specificity of the rt-pcr products was ...19958593411
fusion activity of african swine fever virus towards target membranes: lipid dependence and effect of dehydrating agents.fusion of african swine fever virus (asfv) with model membranes was monitored by a fluorescence dequenching assay. asfv was able to fuse with liposomes of various compositions. fusion was more extensive with liposomes made of negatively charged phospholipids, and reduced in the presence of the neutral phospholipid phosphatidylcholine (pc). fusion activity of asfv was ph-dependent, the extent of fusion increasing with decreasing ph for all target membranes. these results are consistent with the i ...19958595388
differentiation of classical swine fever virus (csfv) strains using monoclonal antibodies against structural glycoproteins.two panels of monoclonal antibodies (mabs) against the classical swine fever virus (csfv) envelope glycoproteins e2 (12 mabs) and e0 (11 mabs) were established and tested by immunoperoxidase binding assay against 135 pestivirus strains and isolates. variability of the binding pattern was demonstrated for csfv and also for bovine viral diarrhea virus (bvdv) strains and isolates. the panels of mabs against e2 and e0 led to very different reactivity patterns. particular mabs against e2 reacted with ...19958604543
application of a monoclonal antibody recognizing protein p30 to detect african swine fever virus-infected cells in peripheral blood.monoclonal antibody (mab) 174f11.8 recognizes an epitope of the african swine fever (asf) virus-induced protein, p30, a protein expressed on the plasma membrane of infected cells. this mab has been used to analyze infected cell populations in peripheral blood of experimentally inoculated pigs with a virulent or attenuated asf virus. flow cytometric analysis of peripheral blood at different days postinfection using this mab, showed expression of p30 mainly in the monocyte/macrophage cell lineage. ...19958609199
a pathological study of the perisinusoidal unit of the liver in acute african swine fever.african swine fever is an acute haemorrhagic disease of pigs which may serve as a model for the study of the pathogenesis of other viral haemorrhagic fevers. this paper describes an ultrastructural study of the sequence of lesions produced in the perisinusoidal functional unit of the liver of pigs inoculated with the malawi '83 strain of african swine fever virus, which is classified as haemadsorbing and highly virulent. virus replication was observed in kupffer cells and monocytes from three da ...19958525104
functional and molecular characterization of african swine fever virus mutants resistant to phosphonoacetic acid.african swine fever virus (asfv) growth and plaque formation were inhibited by phosphonoacetic acid (paa) concentrations of 200 micrograms/ml or more. one spontaneous mutant and two mutants isolated from mutagenized virus were resistant to paa inhibition and showed practically normal viral dna synthesis in the presence of paa. dna polymerase activity present in the cytoplasmic fraction from cells infected with the mutants required 10-fold higher concentrations of paa for inhibition compared to e ...19958525640
improvement of african swine fever virus neutralization assay using recombinant viruses expressing chromogenic marker genes.antibody neutralization of african swine fever (asf) virus measured by a plaque reduction assay presents frequent difficulties because of the absence or delay in plaque formation by many strains, especially low-passage viruses. to overcome this problem, a new asf virus neutralization test has been developed. the new test consists of a conventional plaque reduction assay in which the viral plaques are detected by expression of marker genes. for the development of this neutralization assay 4 mutan ...19958537464
six antigenic groups within the genus pestivirus as identified by cross neutralization assays.antigenic differences between pestivirus isolates of ruminant and porcine origin were characterized by neutralization assays. first, six different clusters of pestiviruses were identified by clustering cross-neutralization results of 13 pestivirus strains tested against 23 sera. cluster i consisted of four strains of bovine viral diarrhoea virus (bvdv) of bovine origin and two bvdv isolates of porcine origin. cluster ii consisted of one sheep isolate and two porcine bdv isolates. cluster iii con ...19958748547
cytocidal infection of hog cholera virus in porcine bone marrow stroma cell cultures.porcine bone marrow stroma cell (bmsc) cultures producing cells of granulocyte-lineage were established. hog cholera (hc) virus ald and alfort strains replicated in the porcine bmsc cultures showing distinct cytopathic effect (cpe). the differentiation of granulocyte-lineage cells in the cultures ceased after infection with hc virus. polyclonal antibody against the ald strain inhibited completely the development of cpe of the both ald and alfort strains. monoclonal antibodies (mabs) specific to ...19958748554
a set of african swine fever virus tandem repeats shares similarities with sar-like sequences.a group of cross-hybridizing dna segments contained within the ecori restriction fragments u', x and j of a vero cell-adapted strain (ba71v) of african swine fever virus (asfv) were mapped and sequenced. analysis of the nucleotide sequence revealed the presence of a set of long internal repeated sequences composed of five types of tandemly repeat units of about 200 bp. these tandem repeats contain a g-rich core of 10-14 nucleotides surrounded by regions with a high a + t content distributed in o ...19959049318
synthesis of substituted 1-norbornylamines with antiviral activity.the reaction of (+/-)-camphor (7) with triflic anhydride (tf2o) yields the bridgehead triflate 8. the nametkin rearrangement of 8 to 3 was realized by treatment with triflic acid (tfoh). the solvolysis of the bridgehead triflates 3 and 8 in acetonitrile affords the n-acetyl-1-norbornylamines 4 and 9. the pd(0)-catalyzed hydrogenation of 4 and 9 gives the amides 5 and 10. the corresponding 1-norbornylamines 2 and 13 and the n-ethyl derivatives 1, 6, 11, and 12 were obtained by basic hydrolysis or ...19957473574
[localizing the major peptides of african swine fever virus and virus-associated enzymes in the virion structure].african swine fever virus polypeptides with molecular weight of 120, 78, 69, 59, 56, 45, 39, 28, 26, 24, 16, and 14 kd are the major proteins in the purified virions, as shown by electrophoresis and immunoblotting. a mixture of proteases and pancreatic lipase hydrolyzed the polypeptides of 120 and 78 kd in viral preparations at low concentrations of enzymes, polypeptides of 69, 56, 45, 39, 28, and 14 kd disappeared after treatment with this mixture at medium concentrations, and 26 kd polypeptide ...19957477038
[apoptosis in the african swine fever virus-swine mononuclear phagocyte system].routine electronmicroscopic examination of interactions between african swine fever virus and mononuclear phagocytes showed signs of apoptosis as a morphological phenomenon and form of cellular death in an infected culture treated with defective interfering virus particles and in target cells under the effect of virus specific cytotoxic t-lymphocytes. the morphology of induced apoptosis in the aforesaid virus-cell system is illustrated and described in detail.19957477039
[natural killers and cytotoxic lymphocytes in classical hog cholera].the formation of immune mechanisms directed at elimination of infected cells and including the activity of natural killers and cytotoxic lymphocytes was assessed in pigs infected with hog cholera virus. in acute disease natural killer activity in the blood is reduced, while in vaccinal process it is increased. vaccination in parallel with cyclophosphamide immunodepression lead to inhibition of natural killer activity. leukocytes and lymphocytes of immunized pigs can cause cytolysis of autologous ...19957483572
characterization of a ubiquitinated protein which is externally located in african swine fever virions.an antiserum was raised against the african swine fever virus (asfv)-encoded ubiquitin-conjugating enzyme (ubcv1) and used to demonstrate by western blotting (immunoblotting) and immunofluorescence that the enzyme is present in purified extracellular virions, is expressed both early and late after infection of cells with asfv, and is cytoplasmically located. antiubiquitin serum was used to identify novel ubiquitin conjugates present during asfv infections. this antiserum stained virus factories ...19957853518
mapping and sequence of the gene encoding protein p17, a major african swine fever virus structural protein.the gene encoding protein p17, a major structural protein of african swine fever virus, has been mapped and sequenced. protein p17 was purified from dissociated virus by reverse-phase hplc and the amino acid sequence of a peptide obtained after digestion of protein p17 with cyanogen bromide was determined by automated edman degradation. to map the gene encoding protein p17, a mixture of 17-mer oligonucleotides based upon a part of the amino acid sequence was hybridized to cloned african swine fe ...19957856088
analysis of the complete nucleotide sequence of african swine fever virus.we present an analysis of the complete genome of african swine fever virus (asfv) strain ba71v, including 80 kbp of novel sequence and 90 kbp previously reported by several authors. the viral dna is 170,101 nucleotides long and contains 151 open reading frames. structural and/or functional information is available on 113 viral proteins. asfv encodes five multigene families, putative membrane and secreted proteins, and enzymes involved in nucleotide and nucleic acid metabolism (including dna repa ...199511831707
partial sequencing of hog cholera virus alfort strain genome and its comparison with other pestivirus strains.after molecular rna cloning of the alfort strain (alfort/lcrv) of hog cholera virus (hcv), the nucleotide sequence of about 70% of the total genome was determined. this sequence was compared with homologous parts of previously published pestivirus genomes. the average homology with another clone of the alfort strain (alfort/frc) was found to be lower (86.1%) than with brescia strain of hcv (94.3%), while, compared with nadl, osloss and sd-1 (3 different strains of bovine viral diarrhea virus, bv ...19957550401
pestivirus diversity. 19957560298
pathological changes in the renal interstitial capillaries of pigs inoculated with two different strains of african swine fever virus.african swine fever is a viral disease of pigs characterized predominantly by haemorrhagic lesions. this paper reports the lesions observed in the renal interstitial capillaries of pigs inoculated with african swine fever virus strains of differing virulence: the malawi'83 strain (haemadsorbent and highly virulent) and the dominican republic'78 strain (haemadsorbent and moderately virulent). in pigs infected with the malawi'83 strain, petechial haemorrhages and microhaemorrhages were observed 5 ...19957560303
experimental african swine fever: apoptosis of lymphocytes and virus replication in other cells.in order to determine the cause of cellular death of lymphocytes in pigs with acute african swine fever and the relationships between african swine fever virus (asfv) and interstitial cells, ten pigs were inoculated with a highly virulent strain of asfv (malawi '83) and samples taken for ultrastructural study of hepatic and renal interstitial tissues. we demonstrated death by apoptosis of lymphocytes and virus replication in fibroblasts, smooth muscle cells and endothelial cells in the interstit ...19957561784
inactivation of viruses in liquid manure.the stability of some viruses and methods of virus inactivation in liquid manure are reviewed. the authors discuss experimental data on the stability of foot and mouth disease virus, classical swine fever virus, aujeszky's disease virus, african swine fever virus, swine influenza virus, porcine paramyxovirus, bovine virus diarrhoea virus and transmissible gastroenteritis of pigs virus. recommendations and practical advice are given for the choice and application of chemical disinfectants for slu ...19957579641
inhibition of il-2r and sla class ii expression on stimulated lymphocytes by a suppressor activity found in homogenates of african swine fever virus infected cultures.virus free supernatants (vfs) obtained by ultracentrifugation of homogenates of african swine fever (asf) virus infected cultures inhibited the proliferative response and the expression in peripheral blood mononuclear cells of two activation molecules, the il-2 receptor (il-2r) and the swine mhc class ii antigens (sla ii), induced by several stimuli (lectins, pma plus the calcium ionophore a23187 or specific antigen). this inhibition was time dependent: no effect was seen on il-2r expression whe ...19957611879
vectors for the genetic manipulation of african swine fever virus.plasmid vectors designed to facilitate the genetic manipulation of african swine fever virus (asfv) are described. our results demonstrate that the beta-glucuronidase enzyme (gus) can be used to follow gene expression in asfv-infected cells. infectious plaques formed by asfv expressing gus are visually detectable, thus providing a simple and highly sensitive method for the selection of asfv recombinants. these and previous results have allowed us to construct two chimeric gene cassettes that con ...19957612241
production and purification of recombinant african swine fever virus attachment protein p12.the conditions for cultivation of spodoptera frugiperda (sf9) insect cells for production of recombinant baculoviruses have been studied, to scale-up and improve the efficiency of the process for production of the african swine fever virus attachment protein p12 in the baculovirus expression system. it was shown that the total virus and recombinant protein production in insect cells infected with the acp12 recombinant baculovirus were slightly dependent on cell density, but largely dependent on ...19957612242
isolation and characterization of tk-deficient mutants of african swine fever virus.african swine fever virus induces the synthesis of thymidine kinase (tk) in bhk tk-negative cells as an immediate early protein. the tk gene is not essential for growth of asfv in cell culture and a stable viral strain deficient in tk has been isolated (e70ntkp). the genetic lesion of this asfv tk- strain was identified by tk gene nucleotide sequencing, showing a nucleotide deletion leading to a -1 frameshift and a nonsense codon residue downstream of the deletion. the availability of this viabl ...19957625127
comparison of the entire nucleotide and deduced amino acid sequences of the attenuated hog cholera vaccine strain gpe- and the wild-type parental strain ald.we have determined the complete nucleotide sequences of a live attenuated hog cholera virus (hcv) and its progenitor strain. the viral rna of each strain consisted of 12,298 nucleotides including untranslated regions of 373 and 228 bases at the 5' and 3' end, respectively. there was a single large open reading frame spanning 11,697 nucleotides which could encode a large protein of 3,899 amino acids with a calculated molecular weight of 438-kda. we have found 225 nucleotide difference between the ...19957661692
classical swine fever virus: independent induction of protective immunity by two structural glycoproteins.to study which proteins of classical swine fever virus (csfv) are able to confer protective immunity in swine, n-terminal autoprotease, viral core protein, and the three structural glycoproteins were expressed via vaccinia virus recombinants (vvr). csfv proteins synthesized in cells infected with vvr showed migration characteristics on sodium dodecyl sulfate gels identical to those of their respective csfv counterparts. apparently authentic dimerization of the recombinant glycoproteins was obser ...19957666549
african swine fever virus gene j13l encodes a 25-27 kda virion protein with variable numbers of amino acid repeats.the african swine fever virus (asfv) j13l gene encodes a 177 amino acid protein (19.0 kda) with a putative transmembrane domain between residues 32 and 52. there is a potential signal peptide cleavage site at residue 54 and several possible motifs for phosphorylation and myristylation. rabbit antisera raised against a synthetic peptide from the c terminus of the j13l orf identified proteins of 25-27 kda in cells infected with a recombinant vaccinia virus expressing the j13l orf, in asfv-infected ...19957730797
ultrastructural study of the renal tubular system in acute experimental african swine fever: virus replication in glomerular mesangial cells and in the collecting ducts.despite the considerable attention given to kidney lesions in african swine fever (asf), a number of questions remain to be answered. structural and ultrastructural examination showed that a highly virulent isolate of asf virus (malawi 83) replicated in glomerular mesangial cells and renal collecting duct epithelial cells, with hyperplasia of the latter in infected pigs. replication in mesangial cells may be due to their contact with the bloodstream, as well as to their phagocytic capacity and h ...19957733828
a proposed division of the pestivirus genus using monoclonal antibodies, supported by cross-neutralisation assays and genetic sequencing.sixty-six pestiviruses from ruminant and porcine hosts were analysed with a panel of 76 monoclonal antibodies raised against 9 different viruses. reactivity was used to construct epitope similarity maps for all of the viruses. four principal virus subgroups were demonstrated. one subgroup equated to classical swine fever virus (csfv) and included most porcine pestiviruses but none from ruminants. a second subgroup contained mainly viruses of bovine origin, including reference bovine viral diarrh ...19957735309
the role of fibrinolysis in the pathogenesis of the haemorrhagic syndrome produced by virulent isolates of african swine fever virus.the activity of several proteins involved in fibrinolysis and the morphological changes in the blood vessel walls of pigs infected with highly virulent (malawi'83) and moderately virulent (dominican republic '78-dr'78) asf virus isolates were determined. pigs infected with the malawi'83 virus developed an increased fibrinolytic activity due to high plasma levels of tissue-plasminogen activator (t-pa) of 71.3 +/- 22.8 iu/ml (mean +/- sd), which correlated well with an increased activation of inte ...19957740481
cytopathogenicity of classical swine fever virus caused by defective interfering particles.for three independent cytopathogenic isolates of classical swine fever virus, defective rnas were found in infected cells in addition to full-length viral genomes. these rnas represent the genomes of typical defective interfering (di) particles because of strict dependence on a complementing helper virus and interference with the replication of the helper virus. analysis of the di genomes revealed internal deletions of 4,764 nucleotides encompassing the complete structural protein-coding region ...19957745717
further characterization of border disease virus isolates: evidence for the presence of more than three species within the genus pestivirus.the molecular analysis of three ovine pestivirus strains revealed the existence of two distinct groups of sheep-derived pestiviruses, namely "true" border disease virus strains (bdv) and bovine viral diarrhea virus (bvdv)-like strains. as an extension of these studies rt-pcr and nucleotide sequencing of the autoprotease (npro) and nucleocapsid protein (c) encoding regions of additional serologically defined ovine pestivirus strains were performed. a comparison of npro and c revealed that three o ...19957747470
promoter analysis of an african swine fever virus gene encoding a putative elongation factor. 19957758704
highly specific confirmatory western blot test for african swine fever virus antibody detection using the recombinant virus protein p54.a western blot technique using a recombinant protein has been developed to confirm positive results obtained in african swine fever (asf)-specific antibody detection by elisa. the new confirmatory western blot is based on the use of protein p54, one of the most antigenic asf virus structural proteins, expressed in escherichia coli fused to the n-terminus of ms2 polymerase. the recombinant western blot assay was highly specific and equally sensitive for asf virus-infected pigs detection as the co ...19957769024
assessment of safety and protective value of a cell culture modified strain "c" vaccine of hog cholera/classical swine fever virus.the protective value of a commercial strain "c" vaccine of classical swine fever (csf) was tested in weaner pigs. vaccinated animals were challenged intranasally with the virulent hog cholera virus (hcv) strain alfort/187 in groups of four pigs each at one to four weeks post vaccination, respectively. non-vaccinated control animals were challenged in the same manner. some vaccinated pigs seroconverted as early as one week post vaccination with all pigs yielding neutralizing antibodies (nab) agai ...19957779071
a comparison of three avidin-biotin complex immunoenzyme systems for detection of african swine fever virus antigen in paraffin-embedded tissues.the sensitivity and specificity of 3 avidin-biotin complex (abc) immunostaining systems were compared on paraffin-embedded tissues from african swine fever virus (asfv)-infected pigs. results were also compared with immunofluorescent detection on cryosections of the same tissue for optimal detection of asfv antigen. the abc-alkaline phosphatase (abc-ap) and abc-peroxidase (abc-po) systems were at least as sensitive as direct fluorescent antibody (fa) and 10-fold more sensitive than the abc-gluco ...19957779959
african swine fever interference with foot-and-mouth disease infection and seroconversion in pigs.initial oral infection of pigs with either highly virulent (l-60) or moderately virulent (dr-2) african swine fever virus (asfv), followed in 3 days with exposure to foot-and-mouth disease virus (fmdv) (tongue inoculation and contact), failed to cause fmdv infection or seroconversion in 18 of 22 l-60-infected pigs and 13 of 34 dr-2-infected pigs. of the 13 dr-2-infected pigs remaining free of foot-and-mouth disease (fmd), 2 pigs survived to 24 days without antibody to fmdv, despite constant cont ...19957779962
african swine fever virus infection of skin-derived dendritic cells in vitro causes interference with subsequent foot-and-mouth disease virus infection.highly purified skin-derived dendritic cells (sddcs) isolated from swine skin by a simple novel method were cultured for 24 hours before independent or sequential inoculation with african swine fever virus (asfv) and foot-and-mouth disease virus (fmdv). by avidin-biotin immunohistochemical staining, asfv antigen was detected in 50% of sddcs as early as 1.5 hours postinfection (hpi) and in 80% by 3 hpi when cytopathic effect was noted. cell lysis was detected with fmdv infection as early as 8 hpi ...19957779963
[isolation of the agent of european swine plague from imported frozen wild boar meat].since july 1993 imported frozen meat of wild boars has to be screened for the presence of hcv. the number of taken samples is given by the ministry of health, sport and consumer protection. until august 1994 the total number of 688 samples from different countries, have been examined. three of them were found positive for hcv. the first one (november 1993) was from china, the other two positive samples were sent in one delivery from romania in may 1994.19957781542
role of viral proteins and concanavalin a in in vitro replication of pseudorabies virus in porcine peripheral blood mononuclear cells.we examined the capability of pseudorabies virus (prv) to replicate in vitro in porcine peripheral blood mononuclear cells (pbmc) and characterized the phenotype of infected cells. in addition, we investigated whether inactivation of various prv proteins or the expression of a foreign gene affected this replication. finally, we studied the replication of prv strains in concanavalin a (con a)-stimulated lymphocytes. the replication of prv mutants with inactivated glycoproteins ge or gg, thymidine ...19957782771
genetic recombination of pseudorabies virus: evidence that homologous recombination between insert sequences is less frequent than between autologous sequences.we studied in vivo recombination between a thymidine kinase (tk) negative, glycoprotein e (ge) negative, attenuated strain and a virulent strain of pseudorabies virus (prv) in pigs. to simplify the detection of recombination we inserted different but overlapping (375 bp) parts of the e1 gene of classical swine fever virus into the gg locus of both virus strains. recombination between the e1 sequences of these viruses results in reconstitution of the complete e1 coding sequence and expression of ...19957794111
replication of transfected plasmid dna by cells infected with african swine fever virus.recombinant plasmids containing african swine fever virus (asfv) dna fragments covering all the virus genome were transfected into infected cells in order to detect viral origins of dna replication. plasmid replication was monitored by sensitivity to mboi, which cleaves only replicated, unmethylated dna, and resistance to dpni, which cleaves only the same methylated sequence. all the recombinants replicated to a similar extent, indicating that asfv does not use a preferred origin for dna replica ...19957886943
unusual folding regions and ribosome landing pad within hepatitis c virus and pestivirus rnas.a statistically significant folding region is identified in the 5' untranslated region (5'-utr) of hepatitis c virus (hcv), bovine viral diarrhea virus and hog cholera virus. this unusual folding region (ufr) detected in hcv encompasses 199 nucleotides (nt) and coincides with the reported internal ribosome entry site or ribosome landing pad (rlp), as determined by the 5' and 3' deletions [tsukiyama-kohara et al., j. virol. 66 (1992) 1476-1483]. the rna structure predicted in the ufr of hcv consi ...19957890155
an african swine fever virus gene with similarity to the t-lymphocyte surface antigen cd2 mediates hemadsorption.an open reading frame, lmw8-dr, in the african swine fever virus (asfv) genome possesses striking similarity to the lymphocyte membrane antigen cd2. all characterized cd2 domains, including the amino-terminal signal sequence, igv, hinge, igc2, stalk, transmembrane, and proline-rich carboxy cytoplasmic domains, are highly conserved in the asfv gene. critical residues for the binding of the lymphocyte function-associated antigen (lfa-3) and cd59 and for t-cell activation are also partially conserv ...19947907198
characterization and molecular basis of heterogeneity of the african swine fever virus envelope protein p54.it has been reported that the propagation of african swine fever virus (asfv) in cell culture generates viral subpopulations differing in protein p54 (c. alcaraz, a. brun, f. ruiz-gonzalvo, and j. m. escribano, virus res. 23:173-182, 1992). a recombinant bacteriophage expressing a 328-bp fragment of the p54 gene was selected in a lambda phage expression library of asfv genomic fragments by immunoscreening with antibodies against p54 protein. the sequence of this recombinant phage allowed the loc ...19947933107
detection of african swine fever virus protein vp73 in tissues of experimentally and naturally infected pigs. 19947948208
[postmortem findings in swine: non-selected submissions from hog cholera protection areas of 1992 versus selected submissions of 1991-1992].this article presents a survey of death-causes of all spontaneously died pigs, n = 851, from a restricted area in the province of south holland during a 2 1/2 months lasting hog-cholera epizoötic in 1992. 23 pigs from 5 submissions showed a positive ift against hog-cholera virus. those animals and pigs from sero-positive farms were excluded from this survey. the results of the post-mortems were compared with the post-mortem findings of the normally submitted, selected, animals in 1991 and 1992, ...19947974450
border disease virus: delineation by monoclonal antibodies.many ovine pestiviruses from britain and a number of atypical porcine isolates are largely unrecognised by monoclonal antibodies (mabs) specific for reference strains of classical swine fever virus and bovine viral diarrhoea virus (bvdv). additional mabs have therefore been produced using some of these "unreactive" pestiviruses. two of the viruses used were atypical porcine isolates (strains 87/6 and vosges), whilst another had been isolated from a sheep (59386). thirty-three mabs were selected, ...19947979965
nucleotide sequence analysis of the structural gene coding region of the pestivirus border disease virus.border disease virus (bdv) of sheep, an important ovine pathogen, is serologically related to the two other well characterized members of the pestivirus genus of the flaviviridae family, namely bovine viral diarrhea virus (bvdv) and hog cholera virus (hocv). to determine its genetic relationship to bvdv and hocv, the genome of bdv strain, bd-78 encompassing the 5' untranslated region (utr) and structural gene coding region was molecularly cloned and the nucleotide sequence determined. the sequen ...19947985409
detection of a cell line contaminated with hog cholera virus.cell lines from the repository of the american type culture collection were examined for possible contamination with bovine viral diarrhea virus. during testing, hog cholera virus (hcv) was detected in the ib-rs-2 d10 porcine kidney cell line. this variant of hcv was avirulent for pigs and seldom induced detectable concentrations of antibody against reference viruses (hcv-ames or bovine viral diarrhea virus-ny1) in serum of inoculated pigs. additionally, this variant of hcv did not confer protec ...19947989247
classical swine fever: genetic detection and analysis of differences between virus isolates.two pairs of oligonucleotide primers were designed that specifically amplified regions of the classical swine fever virus genome. these products, corresponding to a 671 bp portion of the genes encoding the e1 and e2 (gp33 and gp55) proteins and a 1090 bp portion of the putative polymerase gene, were amplified from eight virus isolates which had been responsible for a series of classical swine fever outbreaks in italy involving both domestic pigs and wild boar. for each virus the fragments were p ...19947996138
insect iridescent virus type 6 encodes a polypeptide related to the largest subunit of eukaryotic rna polymerase ii.cytoplasmic dna viruses encode a dna-dependent rna polymerase (ddrp) that is essential for transcription of viral genes. the amino acid sequences of known large subunits of ddrps contain highly conserved regions. oligonucleotide primers, deduced from two conserved domains [rqp(t/s)lh and nadfdgde] were used in pcr experiments for the detection of the corresponding gene of the genome of insect iridescent virus type 6, also known as chilo iridescent virus (civ). a specific dna product of about 150 ...19948021587
nucleotide sequence of a 55 kbp region from the right end of the genome of a pathogenic african swine fever virus isolate (malawi lil20/1).the nucleotide sequence of a 55098 bp region from the right end of the genome of a virulent african swine fever virus (asfv) isolate (malawi lil20/1) has been determined. translation of the sequence identified 67 major open reading frames (orfs) which are closely spaced and read from both dna strands. at six positions intergenic tandem repeat arrays are found. comparison of the predicted amino acid sequences of encoded proteins with protein sequence databases identified a number of homologies. t ...19948021596
two novel multigene families, 530 and 300, in the terminal variable regions of african swine fever virus genome.here, we describe two novel multigene families (mgf) present in the terminal variable regions of the african swine fever virus (asfv) genome. mgf530 includes at least six related orfs (averaging 530 amino acids) containing four well-conserved domains and amino acid identities ranging from 24 to 55%. mgf300 is composed of three orfs (averaging 300 amino acids) containing three highly conserved domains and amino acid identities ranging from 25 to 46%. amino terminal regions of predicted mgf530 and ...19948030263
nucleotide sequence of the telomeric region of the african swine fever virus genome.the 4-kb terminal bcli fragment of african swine fever virus (asfv) dna, including the inverted terminal repetition (itr), was cloned and sequenced. the sequence showed that the 2.1-kb itr is composed of a 301-nucleotide-long unique sequence immediately adjacent to the terminal hairpin loop, a set of 38 tandem direct repeats of a 34-nucleotide degenerate sequence, another unique intervening sequence with no remarkable features, and a set of 5 tandem repeats of a 27-nucleotide unit unrelated in s ...19948030278
[bovine virus diarrhea/mucosal disease: a review].infections with the bovine viral diarrhea/mucosal disease virus (bvdv) are widespread and cause a variety of diseases including reproductive disorders, abortion and malformation, pneumoenteritis, thrombocytopenia and mucosal disease. together with the closely related border disease virus of sheep (bdv) and european swine fever virus (csfv), also referred to as hog cholera virus, bvdv is now classified in the genus pestivirus of the flaviviridae family. the bvdv exists in two biotypes, noncytopat ...19948036482
swine-reconstituted scid mice as a model for african swine fever virus infection.injection of swine peripheral blood mononuclear cells into mice with severe combined immunodeficiency (scid), resulted in the stable long-term establishment of a functional swine immune system (scid-sw). swine immunoglobulins were present in the serum of scid-sw mice and swine cells were detected in the blood as well as in lymph nodes and spleen using monoclonal antibodies raised against cell subpopulations. swine lymphocytes from reconstituted scid mice responded in vitro to specific antigens o ...19948046401
attempted transovarial and venereal transmission of african swine fever virus by the iberian soft tick ornithodoros (pavlovskyella) marocanus (acari: ixodoidea: argasidae).transovarial transmission experiments were conducted with three groups of ornithodoros (pavlovskyella) marocanus velu; one group consisted of 27 pairs of adults that had been fed as larvae on a pig with a viremia of 10(7.4) had50/ml of african swine fever virus (asfv). the second and third groups each consisted of 100 pairs of adults fed on a viremic pig (10(4.5) had50/ml) as adults. the first group underwent five gonotrophic cycles over a 554-d period. the second and third groups underwent thre ...19948057310
congenital infection of pigs with ruminant-type pestiviruses.congenital infections of pigs were induced with two ruminant-type pestiviruses isolated from pigs. one of the viruses was bovine viral diarrhoea virus-like and the other border disease virus-like. both produced symptoms similar to those observed with low virulence strains of classical swine fever virus. a striking effect of persistent virus infection in post-natal life was stunting in viraemic animals. it was also shown that a congenitally infected pig shed virus for 2.5 years and in sufficient ...19947806701
reverse transcriptase-pcr assay for detection of hog cholera virus.a reverse transcriptase-pcr strategy was developed for the detection of hog cholera virus. hog cholera virus template was amplified from tissue culture fluids and from tissues and blood of infected pigs, but not from samples containing other pestiviruses. restriction endonuclease analysis identified samples as historic or recent isolates.19947814509
comparison of pestivirus multiplication in cells of different species.twenty-four pestiviruses, comprising 11 from pigs, eight from cattle and five from sheep, were tested for their ability to replicate in cells of porcine, bovine and ovine origin. seven of the viruses were successfully passaged in all three cell types. four porcine isolates (hog cholera virus) replicated to significant titres only in porcine cells. one bovine virus grew well in bovine cells but only poorly in ovine cells and not at all in porcine cells. the remaining 12 viruses could replicate in ...19947817008
high level expression of the envelope glycoprotein (gp53) of bovine viral diarrhoea virus (singer) and its potential use as diagnostic reagent.a 1.74-kb cdna fragment containing the gp53 coding region has been cloned from bovine viral diarrhoea virus (bvdv) strain singer by reverse transcription polymerase chain reaction (rt-pcr). sequence analysis indicated that gp53 of bvdv strains singer, nadl and sd-1 shared extensive sequence homology at both the rna (85-94%) and protein (82-91%) levels. nineteen cysteine residues and five potential n-linked glycosylation sites were identified within the sequenced region, all of which were conserv ...19947856309
comparative analysis of the 5' non-coding region of pestivirus rna detected from live virus vaccines.comparative analysis of nucleotide sequences in the 5' non-coding region (ncr) of pestivirus rna detected from live porcine and human virus vaccines indicated that the contaminants are of bovine viral diarrhea virus (bvdv), and that there are at least three genotypes, which are distinct from hog cholera virus, among the bvdv strains. most of the nucleotide changes in variable regions of the 5' ncr were covariant, with complementary substitutions at other positions for secondary structures. the p ...19947865600
chilo iridescent virus encodes a putative helicase belonging to a distinct family within the "dead/h" superfamily: implications for the evolution of large dna viruses.the complete nucleotide sequence of the ecori dna fragment m (7099 bp; 0.310-0.345 map units) of the genome of insect iridescent virus type 6--chilo iridescent virus (civ)--was determined. a 606 codon open reading frame located in this region encoded a protein (p69) related to a distinct family of putative dna and/or rna helicases belonging to the "dead/h" superfamily. unique sequence signatures were derived that allowed selective retrieval of the putative helicases of the new family from amino ...19948073636
porcine immune responses to african swine fever virus (asfv) infection.immune responses mediating protection against asfv are poorly understood. anti-asfv antibodies may influence the course of the clinical disease but they have never been found to neutralize the virus. recent developments on cellular defense mechanisms, using swine protection models, and on the induction and role of some cytokines warrant further investigation on these areas.19947856069
[lice and methods of control].the morphology and biology of sucking lice (anoplura) and biting lice (mallophaga) are described. a table shows the main species for given hosts and provides simplified keys for identification. lice have a direct pathogenic effect (damage to skin and cutaneous appendages, fall in productivity) and an indirect effect (transmission of rickettsia prowazeki, r. quintana and borrelia recurrentis in human beings; african and classical swine fever virus, equine infectious anaemia virus and dipylidium c ...19947711304
[glycoproteins from the african swine fever virus].the composition of african swine fever virus (asfv) glycoproteins was studied. isolate-specific major gp 110-140 was identified by radioimmunoprecipitation in lysate of porcine bone marrow cells infected with hemadsorbing virus strains. carbohydrates constitute about 50% of the total mass of gp 110-140. a quantitative method is proposed for identification of the serologic relationships between asfv hemadsorbing strains. a possible role of asfv glycoprotein carbohydrates in the hemadsorption, vir ...19947716925
african swine fever virus structural protein p72 contains a conformational neutralizing epitope.we have previously described a monoclonal antibody (mab 135d4) to an unidentified 70- to 72-kda african swine fever virus (asfv) protein that exhibited high levels of neutralizing activity against various virulent asfv isolates. here, we identify the reactive asfv protein as the major virus structural protein p72. in vitro-translated products of the p72 protein gene were specifically immunoprecipitated by mab 135d4. immunoprecipitation of a nested set of truncated p72 in vitro translation produc ...19947514322
antigenic structure of envelope glycoprotein e1 of hog cholera virus.envelope glycoprotein e1 (gp51 to gp54) is the most antigenic protein of hog cholera virus or classical swine fever virus (csfv). four antigenic domains, a to d, have been mapped on e1 with a panel of monoclonal antibodies (mabs) raised against csfv strain brescia. the boundaries of these domains have been established by extensive studies on binding of mabs to transiently expressed deletion mutants of e1 (p. a. van rijn, e. j. de meijer, h. g. p. van gennip, and r. j. m. moormann, j. gen. virol. ...19947514680
the influence of protease inhibitors of the organism, especially bovine aprotinin, on the production of virulent hog cholera virus in tissue cultures.the influence of biological protease inhibitors, especially aprotinin, on the production of virulent hog cholera virus in cell cultures. production of number and size of fluorescent plaques after infection pk 15 cells with hc virus depended on properties of fetal calf sera added to the medium. by affinity chromatography on bovine alpha-chymotrypsin bound to cm-cellulose inhibitory proteins against chymotrypsin-like proteases could be eliminated from inhibiting sera. the fraction free from inhibi ...19947516855
rapid characterization of new pestivirus strains by direct sequencing of pcr-amplified cdna from the 5' noncoding region.reverse transcription coupled with the polymerase chain reaction (rt-pcr) was used for the rapid laboratory diagnosis of pestivirus infections. a direct dna sequencing method was developed for the analysis of the amplified cdna from the 5' noncoding region of the viral genome. 70 pestivirus strains were compared in this study. sequence analysis allowed the characterization of each isolate as either classical swine fever virus (csfv), bovine viral diarrhea virus, or border disease virus, respecti ...19947529990
uses of flow cytometry in virology.this article reviews some of the published applications of flow cytometry for in vitro and in vivo detection and enumeration of virus-infected cells. sample preparation, fixation, and permeabilization techniques for a number of virus-cell systems are evaluated. the use of flow cytometry for multiparameter analysis of virus-cell interactions for simian virus 40, herpes simplex viruses, human cytomegalovirus, and human immunodeficiency virus and its use for determining the effect of antiviral comp ...19947530594
virulence and pathogenesis of non-virulent and virulent strains of pseudorabies virus expressing envelope glycoprotein e1 of hog cholera virus.pseudorabies virus (prv) expressing the envelope glycoprotein e1 (e1) of hog cholera virus (hcv) was used as a model to study the potential risks connected with the use of a live herpesvirus vaccine expressing a foreign gene. the gene encoding e1 was inserted into the glycoprotein x (gx) locus of both a virulent prv strain and a non-virulent prv strain in which the virulence genes encoding glycoprotein i (gi) and thymidine kinase (tk) had been inactivated. we investigated whether strain m205 (gi ...19948113720
identification of genes encoding zinc finger proteins, non-histone chromosomal hmg protein homologue, and a putative gtp phosphohydrolase in the genome of chilo iridescent virus.five rna transcripts of about 1.2 to 1.7 kilobases were mapped to a part of the genome of insect iridescent virus type 6 (chilo iridescent virus; civ) between genome coordinates 0.832 and 0.856 within the ecori dna fragment f. the nucleotide sequence of this particular region (5702 base pairs) of the civ genome was determined. the dna sequence contains a number of perfect direct, inverted, and palindromic repeats including three clusters of tandemly organized repetitive dna elements located betw ...19948121799
genetic identification and nucleotide sequence of the dna polymerase gene of african swine fever virus.the dna polymerase gene of african swine fever virus (asfv) was mapped by marker rescue experiments using a phosphonoacetic acid-resistant mutant and hybridization with an oligonucleotide probe designed from the most conserved motif of family b dna polymerases. viral dna fragments mapping in this region were cloned and sequenced. an open reading frame coding for a 1244 amino acid long peptide with a molecular mass of 142.5 kda was determined from the sequence. a unique feature of asfv dna polyme ...19948121806
[field infection with bvd virus in swine: epidemiology and diagnosis].in a pig breeding herd in lower saxony infertility of breeding sows had been repeatedly observed. growth retardation and post mortem findings in two piglets gave clinical indication to swine fever/hog cholera. a virus was isolated and typed by monoclonal antibodies as pestivirus not identical with hog cholera virus (hcv). in neutralization tests applying the field isolate, hcv and bovine viral diarrhea (bvd) virus the sera breeding sows and weaner pigs yielded high neutralizing antibody titres a ...19948131728
[prevalence of antibodies against the viruses of european swine fever, aujeszky's disease and "porcine reproductive and respiratory syndrome" in wild boars in the federal states sachsen-anhalt and brandenburg].during the hunting season from 1991/1992 blood samples were collected from wild boar shot in the federal states of sachsen-anhalt (482 samples) and brandenburg (177 samples) which corresponds to 2.1 and 0.4% of the total hunting bag. all sera were screened in a complex trapping blocking (ctb) elisa for antibodies against hog cholera virus (hcv) and in an indirect elisa for antibodies against aujeszky's disease virus (adv). additionally the sera were tested for neutralizing antibodies against hcv ...19948131731
multigene families in african swine fever virus: family 505.sequencing of restriction fragment ecori a-sali c of african swine fever virus has revealed the existence of a multigene family, designated family 505 because of the average number of amino acids in the proteins, composed of seven homologous and tandemly arranged genes. all the genes of family 505 are expressed during infection. primer extension analysis showed that transcription is initiated a short distance (3 to 62 nucleotides) from the start codon of the corresponding open reading frame. the ...19948139051
monoclonal antibodies to bovine viral diarrhea virus: cross-reactivities to field isolates and hog cholera virus strains.monoclonal antibodies to bovine viral diarrhea virus (bvdv) were examined for binding with a large number of north american bvdv isolates and eight strains of the serologically related pestivirus, hog cholera virus (hcv). no single bvdv monoclonal antibody reacted with all bvdv isolates. the most cross-reactive monoclonal antibody was an anti-p80/p125 antibody which showed a positive reaction with 173 of 180 (96%) north american isolates. from a fewer number of isolates tested, one anti-gp53 mon ...19948143258
a rapid and sensitive chemiluminescence dot-immunobinding assay for screening hybridoma supernatants.the present report describes a simple and rapid dot-immunobinding assay combined with a chemiluminescence detection system for screening hybridoma supernatants for specific monoclonal antibodies (mabs). small rectangular nitrocellulose filters dotted with either crude mixtures of antigens, or with control samples, were placed in six well plates, incubated with hybridoma supernatants, then stained with peroxidase-conjugated anti-mouse igg. the reaction was performed with a chemiluminescence detec ...19948157996
epidemiology of classical swine fever in sardinia: a serological survey of wild boar and comparison with african swine fever.a serological survey was carried out to establish the distribution of classical swine fever among wild boar in sardinia, where that disease and african swine fever have been endemic in free-ranging domestic pigs and wild boar living in the mountainous areas of the province of nuoro for several years. blood samples were collected from 4752 wild boar shot during the period december 1988 to january 1992. an overall prevalence of 11 per cent was observed and the almost constant rate of about 9.8 per ...19948171792
glycoprotein e2 of classical swine fever virus: expression in insect cells and identification as a ribonuclease.two regions of amino acids homologous to the ribonuclease catalysis domain of the fungal rnases t2 of aspergillus oryzae and rh of rhizopus niveus and the plant s-glycoproteins of nicotiana alata are perfectly conserved in the amino acid sequence of the envelope glycoprotein e2 of classical swine fever virus (csfv). to analyze the functional significance of these conserved sequences, the gene encoding e2 was inserted into the p10 locus of baculovirus and expressed in insect cells. recombinant vi ...19948178442
nucleotide sequence and variability of the inverted terminal repetitions of african swine fever virus dna.african swine fever virus (asfv) genome is a large (170-190 kb) double-stranded dna molecule with structural features similar to those of poxviruses. prominent among those features are the presence of a hairpin loop structure at the end of the dna molecule and terminal-inverted repeats (tir). the tirs have been previously demonstrated by electron microscopy and cross-hybridization of terminal restriction fragments. we have determined the sequence of both left and right dna ends from the ba71v vi ...19948178480
molecular characterization of border disease virus, a pestivirus from sheep.three serologically different pestivirus strains isolated from sheep were selected for molecular analysis. cdna and deduced amino acid sequences of the genomic regions encoding glycoproteins e1 and e2 were obtained from the three strains. a comparison with amino acid sequences of bovine viral diarrhea virus (bvdv) and classical swine fever virus (csfv) revealed that one of the three ovine pestivirus strains can be grouped together with bvdv. the other two strains, however, were clearly different ...19948291236
long-term persistent infection of swine monocytes/macrophages with african swine fever virus.long-term persistent infection was established in 100% of pigs (n = 19) experimentally infected with african swine fever virus (asfv). viral dna was detected in peripheral blood mononuclear leukocytes (pbml) at greater than 500 days postinfection by a pcr assay. infectious virus was not, however, isolated from the same pbml samples. in cell fractionation studies of pbml, monocytes/macrophages were found to harbor viral dna during the persistent phase of infection. this result indicates that mono ...19948254776
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