Antibody recognition of SIVmac envelope peptides in plasma from macaques experimentally infected with SIV/Mne

Four stretches of amino acid sequences encoded in conserved HIV-1 env domains and four parallel regions of the SIVmac env (two from gp120 and two from gp41/p32E) were fused to the NH2 terminus of beta-galactosidase by recombinant DNA techniques and used to analyze sera from three macaque species experimentally infected with SIV/Mne. All SIVmac env sequences were recognized by sera from the SIV/Mne-inoculated macaques. Western blot analysis performed with whole SIV/Mne, SIVmac, SIVagm, and HIV-1 antigens and sera from SIV/Mne-infected macaques also demonstrates that SIV/Mne is immunologically more closely related to SIVmac than to SIVagm or to HIV-1. Antibody levels to the gp120 NH2-terminal SIV-88 epitope appear to decrease in the infected Macaca nemestrina with progression of disease, as was also reported for the parallel HIV-1 epitope in HIV-1-infected individuals. Sera from all infected macaques reacted with the p32E-SIV-582 epitope (EKYLEDQAQLNAWGCAFRQVC). High titers to this immunodominant epitope could be detected at least 9 weeks postinfection and at a time when primarily the p28 and p32E antibodies were detectable in Western blots performed with whole disrupted SIV/Mne virus. In the majority of animals, antibody titers of 1:100,000 to SIV-582 develop during the infection and persist until death. Antibody responses to the SIV env epitopes in SIV/Mne-infected macaques thus resemble in many aspects (prevalence and immunogenicity) those observed previously for the corresponding HIV-1 env epitopes in HIV-1-infected humans.

Selective replication of simian immunodeficiency virus in a subset of CD4+ lymphocytes

Although all CD4+ cells theoretically are at risk for infection by human immunodeficiency viruses or the related simian immunodeficiency viruses found in Old World monkeys, only a small proportion of CD4+ lymphocytes from infected individuals have detectable virus. This suggests that immunodeficiency viruses may replicate predominantly in a minor subset or activated form of CD4+ T cells, a possibility we examined in macaques infected with a simian immunodeficiency virus isolate, SIV/Mne. Macaque CD4+ lymphocytes could be divided into two subtypes that differed in their level [high (hi) or low (lo)] of expression of a class of heterotypic adhesion receptors (HARs). In blood from animals infected with SIV/Mne, HARhi CD4+ T cells were lost selectively compared to HARlo CD4+ cells and, when cultured, exhibited 50-fold more recoverable reverse transcriptase activity. The HARhi CD4+ subset was also markedly more susceptible to productive infection following exposure to SIV/Mne in vitro. Both subsets are composed primarily of small resting lymphocytes. However, HARhi cells respond differentially to mitogenic stimulation and may thus be more likely to provide the cellular factors necessary to initiate or enhance virus replication. Thus, HAR expression may prove useful both as a prognostic indicator in immunodeficiency virus infection and as a tool to analyze pathogenesis of immunodeficiency viruses.

Antiviral effects of 3'-azido-3'-deoxythymidine, 2',3'-dideoxycytidine, and 2',3'-dideoxyadenosine against simian acquired immunodeficiency syndrome-associated type D retrovirus in vitro

The simian acquired immunodeficiency syndrome (SAIDS) in macaques at the Washington Regional Primate Research Center is associated with a type D retrovirus known as SAIDS-D/WA. We tested the ability of 3'-azido-3'-deoxythymidine (AZT), 2',3'-dideoxycytidine (ddC), and 2',3'-dideoxyadenosine (ddA) to inhibit the in vitro cytopathic effect (syncytium formation) and infectivity of the SAIDS-D/WA virus. Raji cell cultures were infected with virus and treated with various concentrations of AZT, ddC, and ddA. The ability of these drugs to inhibit replication of the SAIDS-D/WA virus in Raji cells was monitored by syncytium formation, expression of viral antigen, and reverse transcriptase assay. At concentrations of 4, 40, and 400 microM, AZT completely blocked the viral infectivity and inhibited the cytopathic effect of SAIDS-D/WA. Likewise, ddC was inhibitory at concentrations of 5 and 50 microM and ddA was inhibitory at 100 and 200 microM. AZT, ddC, and ddA became cytostatic to Raji cells with increasing drug concentrations. AZT also partially inhibited SAIDS-D/WA replication in previously infected Raji cell cultures, and viral inhibition increased in response to the concentration of AZT. These data indicate that AZT, ddC, and ddA are effective antiretroviral agents that merit further evaluation, including clinical trials, in animal models with AIDS-like diseases.

Molecular characterization of gag proteins from simian immunodeficiency virus (SIVMne)

A simian immunodeficiency virus (SIV) designated SIVMne was isolated from a pig-tailed macaque with lymphoma housed at the University of Washington Regional Primate Research Center, Seattle. To better establish the relationship of SIVMne to other immunodeficiency viruses, we purified and determined the partial amino acid sequences of six structural proteins (p1, p2, p6, p8, p16, and p28) from SIVMne and compared these amino acid sequences to the translated nucleotide sequences of SIVMac and human immunodeficiency virus types 1 and 2 (HIV-1 and HIV-2). A total of 125 residues of SIVMne amino acid sequence were compared to the predicted amino acid sequences of the gag precursors of SIV and HIVs. In the compared regions 92% of the SIVMne amino acids were identical to predicted residues of SIVMac, 83% were identical to predicted residues of HIV-2, and 41% were identical to predicted residues of HIV-1. These data reveal that the six SIVMne proteins are proteolytic cleavage products of the gag precursor (Pr60gag) and that their order in the structure of Pr60gag is p16-p28-p2-p8-p1-p6. Rabbit antisera prepared against purified p28 and p16 were shown to cross-react with proteins of 60, 54, and 47 kilodaltons present in the viral preparation and believed to be SIVMne Pr60gag and intermediate cleavage products, respectively. SIVMne p16 was shown to contain covalently bound myristic acid, and p8 was identified as a nucleic acid-binding protein. The high degree of amino acid sequence homology between SIVs and HIV-2 around proven proteolytic cleavage sites in SIV Pr60gag suggests that proteolytic processing of the HIV-2 gag precursor is probably very similar to processing of the SIV gag precursor. Peptide bonds cleaved during proteolytic processing of the SIV gag precursor were similar to bonds cleaved during processing of HIV-1 gag precursors, suggesting that the SIV and HIV viral proteases have similar cleavage site specificities.

Isolation and characterization of a novel protein (X-ORF product) from SIV and HIV-2

A protein designated p14 was purified from a simian immunodeficiency virus (SIVMne) and was shown by amino acid sequence analysis to be nearly identical to the predicted translational product of a unique open reading frame (X-ORF) in the nucleotide sequences of SIVmac and human immunodeficiency virus type 2 (HIV-2). Thus the X-ORF is proven to be a new retroviral gene. The p14 is present in SIVMne in molar amounts equivalent to those of the gag proteins. This is the first example of a retrovirus that contains a substantial quantity of a viral protein that is not a product of the gag, pro, pol, or env genes. SIV p14 and its homolog in HIV-2 may function as nucleic acid binding proteins since purified p14 binds to single-stranded nucleic acids in vitro. Antisera to the purified protein detected p14 in SIVMne, SIVmac, and a homologous protein (16 kilodaltons) in HIV-2 but did not react with HIV-1. Diagnostic procedures based on this novel protein will distinguish between HIV-1 and HIV-2.

Inoculation of baboons and macaques with simian immunodeficiency virus/Mne, a primate lentivirus closely related to human immunodeficiency virus type 2

A primate lymphotropic lentivirus was isolated on the human T-cell line HuT 78 after cocultivation of a lymph node from a pig-tailed macaque (Macaca nemestrina) that had died with malignant lymphoma. This isolate, originally designated M. nemestrina immunodeficiency virus (MnIV) and now classified as simian immunodeficiency virus (SIV/Mne), was inoculated intravenously into three juvenile rhesus monkeys (Macaca mulatta), three juvenile pig-tailed macaques (M. nemestrina), and two juvenile baboons (Papio cynocephalus). All six macaques became viremic by 3 weeks after inoculation, whereas neither of the baboons developed viremia. One pig-tailed macaque died at 15 weeks with suppurative peritonitis secondary to ulcerative, necrotizing colitis. Immunologic abnormalities included a marked decrease in CD4+ peripheral blood lymphocytes. Although five macaques mounted an antibody response to SIV/Mne, the animal that died at 15 weeks remained antibody negative. Three other macaques (two rhesus and one pig-tailed) died 66 to 87 weeks after inoculation after exhibiting progressive weight loss, anemia, and diarrhea. Histopathologic findings at necropsy included various manifestations of immune deficiency, nephropathy, subacute encephalitis, pancreatitis, adenocarcinoma, and lymphoid atrophy. SIV/Mne could be readily isolated from the spleens and lymph nodes of all necropsied macaques, and from the cerebrospinal fluid, brains, bone marrow, livers, and pancreas of some of the animals. SIV antigens were localized by avidin-biotin immunohistochemistry to pancreatic islet cells and to bone marrow endothelial cells. The data suggest that African baboons may be resistant to infection by SIV/Mne, whereas Asian macaques are susceptible to infection with this pathogenic primate lentivirus.

Isolation of a lentivirus from a macaque with lymphoma: comparison with HTLV-III/LAV and other lentiviruses

A retrovirus has been isolated on the human T-cell line HuT 78 after cocultivation of a lymph node from a pig-tailed macaque (Macaca nemestrina) that had died with malignant lymphoma in 1982 at the University of Washington primate center. This isolate, designated MnIV (WPRC-1) (M. nemestrina immunodeficiency virus, Washington Primate Research Center) shows the characteristic morphology of a lentivirus and replicates to high titers in various lymphocyte lines of human and primate origin. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of purified MnIV revealed multiple bands of structural proteins, including a major viral gag protein of 28 kilodaltons, that did not comigrate with the viral proteins of a human immunodeficiency virus (HIV [FRE-1]) that was also isolated on HuT 78 cells. The relatedness of MnIV to other lentiviruses (HTLV-III/LAV, EIAV, and visna) was examined in radioimmunoassays, by immunoblot techniques, and by N-terminal amino acid sequence analysis of the viral p28 gag protein. The immunoassays revealed cross-reactivity only between MnIV p28 and HTLV-III/LAV p24, and sequence analysis showed that 14 of the 24 N-terminal residues of MnIV p28 and HTLV-III/LAV p24 are identical. These results indicate that MnIV belongs to the same lentivirus family as HTLV-III/LAV but is only partially related to these human acquired immune deficiency syndrome retroviruses.

Retroperitoneal fibromatosis and acquired immunodeficiency syndrome in macaques: clinical and immunologic studies

A simian acquired immunodeficiency syndrome (SAIDS) associated with retroperitoneal fibromatosis (RF) has been observed in several species of macaque at the Washington Regional Primate Research Center. Clinical signs were recurrent diarrhea, weight loss, mesenteric lymphadenopathy, and opportunistic infections. Most affected macaques in the later stages of illness showed marked immunodeficiency. Response of peripheral blood mononuclear cells to mitogens was impaired significantly. There was sharply depressed primary and secondary antibody response to the T-cell dependent antigen, bacteriophage phi X174. Affected monkeys did not switch from IgM to IgG antibody following a secondary immunization, as did normal macaques. Twenty-four (67%) of 36 affected animals with progressive RF or deteriorated stages of illness had hypoproteinemia and hypoalbuminemia. Quantitative serum immunoglobulins of 23 cases showed that eight (35%) had hypogammaglobulinemia, six (26%) had hypergammaglobulinemia, and the remainder (39%) were within the normal range. Opportunistic infections were predominantly bacterial pathogens. Type D retrovirus appeared to be closely associated with RF-affected macaques (12/12 or 100%). The case fatality rate (including animals sacrificed after prolonged illness) was 98%. The leading cause of death was due directly to RF lesions in 43%, to enterocolitis in 36%, septicemia in 12%, amyloidosis in 5%, and malignant lymphoma (2%). Clinical, immunologic and pathologic changes reveal an acquired immunodeficiency syndrome that has many similarities to human AIDS. SAIDS and RF may be a useful model for studying human AIDS.

Retroperitoneal fibromatosis and acquired immunodeficiency syndrome in macaques: epidemiologic studies

At the University of Washington Regional Primate Research Center, a simian acquired immunodeficiency syndrome (SAIDS) associated with retroperitoneal fibromatosis (RF) has been observed in 82 macaques since 1976, including 77 pigtailed macaques (Macaca nemestrina), two long-tailed macaques (M. fascicularis), one Japanese macaque (M. fuscata) and two rhesus macaques (M. mulatta). The syndrome is characterized by immunodeficiency accompanied by a fibroproliferative lesion, primarily affects young monkeys (1-3 years) and has a high case fatality rate. Based on the occurrence of RF in colony-born and non-colony-born monkeys, the minimum incubation period for natural exposure is believed to be about 9 months. The incidence of RF was 0.9% in M. nemestrina, 0.1% in M. fascicularis, 1.0% in M. fuscata and 0.4% in M. mulatta. There were no significant differences in the incidence of RF by sex or seasonality. Epidemiologic studies were focused on 42 juvenile M. nemestrina that developed RF between January 1980 and June 1983, and the results were compared with 42 age- and sex-matched controls. The incidence of RF was 5.7% in monkeys 12-24 months old and 3.4% in monkeys 24-36 months old, but less than 1.0% in age groups of under 1 year and over 3 years. No significant associations were found for housing history, parentage, generations or ancestral origins. Epidemiologic information and preliminary viral studies suggest a type D retrovirus may be the causative agent in RF and SAIDS. RF associated with SAIDS appears to be an excellent model for Kaposi's sarcoma associated with human AIDS.

A molecular solution to the riddle of the giant panda's phylogeny

Although it is generally agreed that the giant panda (Ailuropoda melanoleuca) is a member of the order Carnivora, there has long been disagreement over whether it should be classified with bears, raccoons or as a single member of its own family. Four independent molecular and genetic measures lead to a consensus phylogeny for the giant and lesser pandas. The lesser panda diverged from New World procyonids at approximately the same time as their departure from ursids, while ancestors of the giant panda split from the ursid lineage much later, just before the radiation which led to modern bears. The giant panda's divergence was accompanied by a chromosomal reorganization which can be partially reconstructed from the ursid karyotype, but not from that of procyonids or the lesser panda. The apparently dramatic, but actually limited, distinctions between the giant panda and the bears in chromosomal and anatomical morphology provide a graphic mammalian example of the discordance of molecular and morphological (and chromosomal) evolutionary change.

Purification and N-terminal amino acid sequence comparisons of structural proteins from retrovirus-D/Washington and Mason-Pfizer monkey virus

A new D-type retrovirus originally designated SAIDS-D/Washington and here referred to as retrovirus-D/Washington (R-D/W) was recently isolated at the University of Washington Primate Center, Seattle, Wash., from a rhesus monkey with an acquired immunodeficiency syndrome and retroperitoneal fibromatosis. To better establish the relationship of this new D-type virus to the prototype D-type virus, Mason-Pfizer monkey virus (MPMV), we have purified and compared six structural proteins from each virus. The proteins purified from each D-type retrovirus include p4, p10, p12, p14, p27, and a phosphoprotein designated pp18 for MPMV and pp20 for R-D/W. Amino acid analysis and N-terminal amino acid sequence analysis show that the p4, p12, p14, and p27 proteins of R-D/W are distinct from the homologous proteins of MPMV but that these proteins from the two different viruses share a high degree of amino acid sequence homology. The p10 proteins from the two viruses have similar amino acid compositions, and both are blocked to N-terminal Edman degradation. The phosphoproteins from the two viruses each contain phosphoserine but are different from each other in amino acid composition, molecular weight, and N-terminal amino acid sequence. The data thus show that each of the R-D/W proteins examined is distinguishable from its MPMV homolog and that a major difference between these two D-type retroviruses is found in the viral phosphoproteins. The N-terminal amino acid sequences of D-type retroviral proteins were used to search for sequence homologies between D-type and other retroviral amino acid sequences. An unexpected amino acid sequence homology was found between R-D/W pp20 (a gag protein) and a 28-residue segment of the env precursor polyprotein of Rous sarcoma virus. The N-terminal amino acid sequences of the D-type major gag protein (p27) and the nucleic acid-binding protein (p14) show only limited amino acid sequence homology to functionally homologous proteins of C-type retroviruses.

Characterization of exogenous type D retrovirus from a fibroma of a macaque with simian AIDS and fibromatosis

A novel type D retrovirus was isolated by cocultivation of explants of fibromatous tissue from a rhesus monkey (Macaca mulatta) with immunodeficiency and retroperitoneal fibromatosis. This type D virus, isolated from a macaque with simian acquired immunodeficiency syndrome (SAIDS-D/Washington), is exogenous and is partially related to the Mason-Pfizer and the langur monkey type D viruses. The SAiDS-D virus can be distinguished from all other primate retroviruses by antigenicity and molecular hybridization. Nucleic acid hybridization studies reveal that the origin of the SAIDS-D isolate may reside in Old World monkey (subfamily Colobinae) cellular DNA.

A gene (Bevi) on human chromosome 6 is an integration site for baboon type C DNA provirus in human cells

Human VA-2 cells infected with baboon type C virus were cloned and fused to Syrian hamster cells, and 33 primary hybrid colonies were obtained. These cells segregated human chromosomes and retained the complete hamster genome. Assays for type C viral p30 antigen and reverse transcriptase were performed in conjunction with analyses of 30 gene-enzyme systems representing 22 different human chromosomes. The results comfirmed that a gene, Bevi, previously assigned to human chromosome 6, dominantly controls baboon type C virus expression in hybrid cells. Representative hybrid colones were studied by nucleic acid hybridization techniques for the presence of integrated proviral DNA using complementary 3H-DNA transcripts of the baboon viral RNA genome. For each of 12 clones examined, there was a concordance between the presence of human chromosome 6, the presence of baboon type C proviral DNA sequences and virus expression. Clones which segregated chromosome 6 as judged by isozyme and karyological analyses lost detectable proviral DNA sequences and failed to produce virus. No syntenic association between the replication of baboon virus and the presence of 21 other human chromosomes was deteced. We conclude that Bevi is a preferred integration site for the baboon type C provirus in the human genome.

Rescue of endogenous 30S retroviral sequences from mouse cells by baboon type C virus

Mus musculus SC-1 cells were infected with M7 baboon type C virus. The progeny of this infection included viral pseudotypes that contained M7 helper virus and endogenous 30S retrovirus-associated sequences derived from SC-1 cells (RAS). The RAS sequences are unrelated by nucleic acid hybridization criteria to previously described types of murine retroviruses and do not code for known murine viral structural proteins. The RAS genome is present in multiple copies in the DNA of laboratory (M. musculus) and Asian (M. caroli and M. cervicolor) mice, is expressed in the RNA of uninfected mouse cells, and can be efficiently rescued by type C, but not type B, viruses. RAS is closely related to 30S virus-associated RNA in NIH/3T3 and BALB/c JLSV-9 cells and may be analogous to the defective 30S RNA sequences found in rats.

MAC-1, a new genetically transmitted type C virus of primates: "low frequency" activation from stumptail monkey cell cultures

A new class of endogenous primate type C virus has been isolated from a continuous tissue culture line of Macaca arctoides cells by co-cultivation with a human cell line. The virus, designated MAC-1, can be transmitted to human and feline cells in tissue culture, and is unrelated, by immunological and nucleic acid hybridization criteria, to previously characterized retroviral isolates of primates. In particular, MAC-1 shows no detectable homology to the baboon type C viruses, even though viral genes related to the latter group are readily detected in M. arctoides cellular DNA. Viral gene sequences related to the MAC-1 genome are present in multiple copies (50-150 per haploid genome) in Old World primates, and are expressed in the cellular RNAs of uninfected and "virus-free" primate cells and tissues. Thus there are at least two distinct sets of genetically transmitted Old World primate type C viral genes, each of which is found in multiple copies in normal primate cellular DNA. With the description of this new retrovirus, there are now a minimum of five distinct genetically transmitted viruses of primates, three type C and type D, each represented in multiple copies in the normal cellular DNA.

Endogenous mink (Mustela vison) type C virus isolated from sarcoma virus-transformed mink cells

A previously described type virus stock (designated PP-1R), isolated by cocultivating baboon cells with mink cells transformed by Kirsten sarcoma virus (64J1), has been further cloned and characterized. End point-diluted stocks of PP-1R have been obtained that are free of focus-forming activity and lack both Kirsten sarcoma and primate type C viral sequences. Nucleic acid hybridization experiments show that the cloned virus (MiLV) is an endogenous, genetically transmitted virus of the mink (Mustela vison). MiLV replicates in canine, feline, and 64J1 mink cells but not in an untransformed mink cell line. Multiple viral gene copies can be detected in the DNA of normal mink cells in culture and in normal mink tissues; related endogenous viral genes are also detected in several related Mustela species. The virus codes for a p30 protein very closely related antigenically to that of feline leukemia virus but contains p15 and p12 proteins that are antigenically distinct. The mink cell line, Mv1Lu, and its Kirsten sarcoma-transformed derivatives, 64J1, express relatively low levels of type C viral RNA related to MiLV and normally do not produce detectable levels of MiLV p30 protein or complete, infectious viral particles. Infection of sarcoma virus-transformed mink cells with baboon type C virus, however, can augment the level of expression of endogenous mink viral RNA and can result in the synthesis and packaging of mink viral RNA and p30 antigen in extracellular virions. Since the Mv1Lu cell line and its tranformed derivatives have become widely used in studies of retroviruses, the possibility of activating endogenous mink viral genes should be considered by investigators working with these cells.

Two distinct endogenous type C viruses isolated from the asian rodent Mus cervicolor: conservation of virogene sequences in related rodent species

The cocultivation of a lung cell line from the Southeast Asian mouse Mus cervicolor with cells from heterologous species has resulted in the isolation of two new distinct type C viruses. Both viruses are endogenous to M. cervicolor and are present in multiple copies in the cellular DNA of these mice. One of the viruses, designated M. cervicolor type CI, replicates readily in the SIRC rabbit cell line and is antigenically related to the infectious primate type C viruses isolated from a woolly monkey (simian sarcoma-associated virus) and gibbon apes (gibbon ape leukemia virus). This virus is also closely related by both immunological and nucleic acid hybridization criteria to a type C virus previously isolated from a second Asian murine species, Mus caroli. The isolation of the M. cervicolor type C I virus thus provides further evidence that the infectious primate type C viruses originated by trans-species infection of primates by an endogenous virus of mice. The second virus, designated M. cervicolor type C II, replicates well in various cell lines derived from the laboratory mouse Mus musculus. While antigenically related to type C viruses derived from M. musculus, the M. cervicolor type C II virus isolate can be readily distinguished from standard murine leukemia viruses. Both new type C viruses from M. cervicolor are unrelated to the previously described retrovirus (M432) isolated from the same Mus species. The DNA of M. cervicolor therefore contains multiple copies of at least three distinct classes of endogenous viral genes. An examination of the cellular DNA of other rodent species for nucleic acid sequences related to the genomes of both M. cervicolor type C I and II reveals that both viruses have been highly conserved evolutionarily, and that other species of rodents, such as laboratory mice and rats, contain endogenous virogenes related to those in the DNA of M. cervicolor.

A new class of genetically transmitted retravirus isolated from Mus cervicolor

The cocultivation of spleen cells from the Southeast Asian mouse, Mus cervicolor, with heterologous cell lines has permitted the isolation of a new retravirus (designated M432) that can be transmitted to tissue culture cells of the laboratory mouse, M. musculus. Cells infected with M432 contain cytoplasmic type A particles and budding forms with compact,spherical nucleoids; extracellular virions lack surface spikes and have a condensed, central core surrounded by an intermediate line. Like other retraviruses, M432 bands isopycnically in sucrose at 1.16-1.17 g/cm3 and contains a 70S RNA genome composed of 35S subunits and an RNA-dependent DNA polymerase (RNA-dependent DNA nucleotidyltransferase). The viral reverse transcriptase requires magnesium as a cofactor and transcribes the synthetic template:primer poly(rC)-oligo(dG) more efficiently than poly(rA)-oligo(dT). [3H]DNA transcripts of the viral RNA genome detect multiple copies of endogenous virogene sequences in the cellular DNA of normal M. cervicolor, and fewer copies in heterologous cells infected with M432. Partially related nucleic acid sequences are also detected in the DNA of M. caroli and M. musculus as well as in more distantly related species (rat and hamster), reflecting the evolutionary conservation of these gene sequences in rodents. Although the virus from M. cervicolor shares certain morphologic and biochemical properties with murine type B viruses, the new isolate is unrelated by nucleic acid hybridization criteria to the mouse mammary tumor virus, the bovine leukemia virus, the Mason-Pfizer monkey virus, or known murine type C viruses, including endogenous type C viruses isolated from M. cervicolor.

Type C viruses from Kirsten sarcoma-transformed mink cells co-cultivated with primate cells and expressing p30 antigens related to feline leukemia virus

Two type C viruses with new antigenic and biological properties were isolated by co-cultivating secondary cell strains established from the kidneys of a baboon (Papio papio) and a patas monkey (Erythrocebus patas) with mink cells non-productively transformed by Kirsten sarcoma virus. Both new isolates (designated PP-1R and EP-1R) contain major structural proteins (p30) that are immunologically most closely related to the p30 proteins of feline leukemia viruses. The reverse transcriptases of both viruses, although antigenically related to polymerases of murine and rat type C viruses, are distinct from those of previously described type C viral groups. Both PP-1R and EP-1R can be transmitted to canine and feline cells and to sarcoma virus-transformed, but not normal, mink cells. Both viruses contain RNA genomes partially homologous to those of endogenous mouse and rat type C viruses and the Kirsten sarcoma virus. In addition, the RNA of PP-1R contains a portion of the nucleic acid sequences found in a type C virus isolated from the baboon species P. papio. We propose that both new isolates are genetic recombinants formed between endogenous primate type C viral genomes and sequences found in Kirsten sarcoma-transformed mink cells.