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V M Hirsch

Publications and source records attributed to V M Hirsch.

At least 73 records · Page 4Linked to original sources
PubMed1992

Genetic variation of simian immunodeficiency viruses in nonhuman primates.

The generation of biologically active proviral DNA clones of simian immunodeficiency virus (SIV) that give rise to infectious virions has allowed the detailed examination of genetic variation in experimentally inoculated monkeys. Studies of nucleotide sequences derived directly from circulating leukocytes of infected monkeys show that the SIV genome undergoes rapid and dramatic variation during the course of infection. The env gene is a major site for variation, and within the Env protein, hypervariable regions analogous to those previously defined for the human immunodeficiency virus type 1 (HIV-1) env gene are apparent. A major exception is the region corresponding to the V3 domain in HIV-1, which has been highly conserved in all SIV studies to date. These data notwithstanding, the role of SIV genetic variation in the pathogenesis of AIDS in monkeys remains unclear. Genetic variation within the env gene does not appear to be sufficient for the development of AIDS since significant variation is observed in both pathogenic and nonpathogenic SIV infections. Furthermore, although it generally is believed that env gene variation might allow HIV and SIV to avoid recognition and elimination by host immune responses, this premise has not been rigorously proven. The use of molecularly cloned SIV in monkey models has provided important quantitative and qualitative information on in vivo sequence variation, and these data, in turn, have laid the groundwork for addressing the undoubtedly complex functional significance of this variation.

Amino Acid Sequence↗
PubMed1992

Coexpression of the simian immunodeficiency virus Env and Rev proteins by a recombinant human adenovirus host range mutant.

Recombinant human adenoviruses (Ads) that replicate in the intestinal tract offer a novel, yet practical, means of immunoprophylaxis against a wide variety of viral and bacterial pathogens. For some infectious agents such as human immunodeficiency virus (HIV), the potential for residual infectious material in vaccine preparations must be eliminated. Therefore, recombinant human Ads that express noninfectious HIV or other microbial proteins are attractive vaccine candidates. To test such an approach for HIV, we chose an experimental model of AIDS based on simian immunodeficiency virus (SIV) infection of macaques. Our data demonstrate that the SIV Env gene products are expressed in cultured cells after infection with a recombinant Ad containing both SIV env and rev genes. An E3 deletion vector derived from a mutant of human Ad serotype 5 that efficiently replicates in both human and monkey cells was used to bypass the usual host range restriction of Ad infection. In addition, we show that the SIV rev gene is properly spliced from a single SIV subgenomic DNA fragment and that the Rev protein is expressed in recombinant Ad-SIV-infected human as well as monkey cells. The expression of SIV gene products in suitable live Ad vectors provides an excellent system for studying the regulation of SIV gene expression in cultured cells and evaluating the immunogenicity and protective efficacy of SIV proteins in macaques.

Adenoviridae↗
PubMed1992

SIV infection of macaques as a model for AIDS pathogenesis.

Simian immunodeficiency virus (SIV) infection of macaques is the best available animal model for studying the pathogenesis of AIDS. Experimental inoculation of macaques with SIV results in a persistent infection that leads to immunodeficiency, opportunistic infections, and death. Most aspects of the illness, including immunologic and virologic parameters, are easily quantified. Furthermore, pathologic processes can be evaluated throughout the course of experimental infection. Recently, molecular clones of SIV proviral DNA have been used to study genetic variation and specific viral determinants of pathogenesis. Considered together, these observations support the continued detailed study of SIV infection of macaques as a model for human AIDS.

Acquired Immunodeficiency Syndrome↗
PubMed1991

A highly divergent proviral DNA clone of SIV from a distinct species of African green monkey.

Simian immunodeficiency viruses from African green monkeys (SIVagm) are the most genetically heterogeneous type of non-human primate lentivirus. To further examine the extent of genetic divergence within the SIVagm type, we generated and sequenced a biologically active proviral DNA clone representing a lentivirus isolated from a distinct African green monkey species (grivet). Overall, this clone (gri-1/lambda II) was highly divergent from previously characterized SIVagm clones. Specifically, the difference between gri-1/lambda II and other SIVagm clones approximated the difference between the caprine arthritis encephalitis virus and visna virus (two biologically and genetically distinct ruminant lentiviruses). Our data suggest that lentiviruses from African green monkeys may have evolved in concert with speciation of the genus and support the concept that SIVagm may be the oldest primate lentivirus type in existence.

Amino Acid Sequence↗
PubMed1991

The genetic fate of molecularly cloned simian immunodeficiency virus in experimentally infected macaques.

We have examined genetic variation of the simian immunodeficiency virus (SIV) in four macaques inoculated with virions derived from molecular clones of proviral DNA. Our data demonstrated that the SIV genome is capable of rapid and extensive genetic variation. This variation was especially large in the env gene, where nucleotide substitution frequencies were as high as 10(-1)/site/year. In some env clones, a high G to A transition rate was observed that accounted for up to 79% of the observed nucleotide substitutions. Moreover, in env clones with a high G to A transition rate, multiple in-frame stop codons were generated exclusively at tryptophan codons. Another interesting observation was the lack of variation in the region analogous to the V3 loop in the HIV-1 Env protein. Considered together, these data have important implications for studies of pathogenesis and vaccine development in the SIV model system.

Amino Acid Sequence↗
PubMed1991

Simian immunodeficiency virus infection of macaques: end-stage disease is characterized by widespread distribution of proviral DNA in tissues.

Four simian immunodeficiency virus (SIV)-infected macaques in the terminal stages of AIDS were studied. Easily detectable unintegrated proviral DNA was present in nearly every tissue (lymphoid and nonlymphoid) examined. SIV-specific immunohistochemistry revealed that macrophages or macrophage-like cells were the predominant reservoirs for SIV. High burdens of infectious SIV were also characteristic of end-stage disease. At the molecular level, sequence analyses of molecular clones derived directly from tissue demonstrated that SIV, like other RNA viruses, exists as a mixture of closely related genomes. Viruses derived by cocultivation seemed to be selected for their ability to grow in tissue culture and did not represent the wide spectrum of genotypes in tissues. These data indicate that SIV-induced immunodeficiency is a complex, multisystem disease and that SIV replication, in addition to impairing the immune system, may have direct deleterious effects on multiple organ systems.

Amino Acid Sequence↗
PubMed1991

Species-specific diversity among simian immunodeficiency viruses from African green monkeys.

The prevalence, natural history, and genetic characteristics of simian immunodeficiency virus (SIV) infections in most feral African monkey species are presently unknown, yet this information is essential to elucidate their origin and relationship to other simian and human immunodeficiency viruses. In this study, a combination of classical and molecular approaches were used to identify and characterize SIV isolates from West African green monkeys (Cercopithecus sabaeus) (SIVagm isolates). Four SIVagm viruses from wild-caught West African green monkeys were isolated and analyzed biologically and molecularly. Amplification, cloning, and sequencing of a 279-bp polymerase fragment directly from uncultured peripheral blood mononuclear cells was facilitated by the use of nested polymerase chain reaction. The results indicated that West African green monkeys are naturally infected with SIVs which are closely related to East African SIVagm isolates. However, structural, antigenic, and genetic differences were observed which strongly suggest that the West African green monkey viruses comprise a phylogenetically distinct subgroup of SIVagm. These findings support our previous hypothesis that SIVagm viruses may have evolved and diverged coincident with the evolution and divergence of their African green monkey host. In addition, this study describes a polymerase chain reaction-based approach that allows the identification and molecular analysis of divergent SIV strains directly from primary monkey tissue. This approach, which does not depend on virus isolation methods, should facilitate future studies aimed at elucidating the origins and natural history of SIVs in feral African green monkey populations.

Amino Acid Sequence↗
PubMed1991

Molecular diversity of SIVsmm/PBj and a cognate variant, SIVsmm/PGg.

The molecular diversity of SIVsmm/PBj proviral genomes in tissues of an infected macaque was analyzed. Molecular clones derived directly from intestinal tissue DNA were heterogenous, and contained LTRs with one or two NF-kB binding sites. LTRs with one NF-kB site predominated (approximately 75%). Virions derived from biologically active chimeric DNA clones with one or two NF-kB sites did not induce the acute death syndrome characteristic of PBj infection. These results suggest that either the duplicated NF-kB site acts in concert with other important viral determinants, or plays no role in producing the PBj syndrome.

Amino Acid Sequence↗
PubMed1990

Coexpression of biologically active simian immunodeficiency virus (SIV) Rev and Env in an SV40 system: the SIV rev gene regulates env expression.

The coexpression of biologically active simian immunodeficiency virus (SIV) Rev and Env gene products was obtained in COS-1 cells from a single SIV subgenomic segment (which contains both exons of rev and the entire env gene) cloned into a SV40-directed vector. The SIVsm Rev trans-activated the expression of the full-length env mRNA and was required for the production of envelope glycoproteins. Furthermore, the alignment of the structural conservation of the Rev functional domains among all HIV and SIV was analyzed.

Amino Acid Sequence↗
PubMed1990

Antibody-dependent enhancement of simian immunodeficiency virus (SIV) infection in vitro by plasma from SIV-infected rhesus macaques.

Plasma from two rhesus macaques (Macaca mulatta) experimentally infected with the simian immunodeficiency virus (SIV; isolate SIVmac251) enhanced SIVmac infection of a human CD4+ lymphoblastoid cell line, MT-2. Prechallenge plasma samples from these animals and serum from SIV-negative macaques did not enhance infection. Compared with controls, infection enhancement was characterized by the rapid appearance of syncytium formation (3 to 4 days sooner), reverse transcriptase release (10-fold increase), and cytopathic effect (60% cell killing). Enhancement of activity was dependent on the presence of diluted, fresh SIV-negative macaque serum as a source of complement. A requirement for complement was shown by the absence of enhancement in heat-inactivated serum and by dose-dependent inhibition of enhancement in the presence of polyclonal antibody to monkey complement component C3. Monoclonal antibody to CD4 (OKT4a) blocked enhancement completely, while monoclonal antibody to the human complement component C3d receptor CR2 (OKB7) reduced enhancement by greater than 50%, indicating a requirement for CD4 and CR2 in mediating this phenomenon. SIV infection-enhancing activity appeared in macaques soon after experimental inoculation (28 days). The titer increased over time and peaked just prior to the death of both macaques from opportunistic infections and lymphoma. In vitro SIV infection enhancement is nearly identical to the in vitro complement-mediated, antibody-dependent enhancing (C'-ADE) activity observed in human immunodeficiency virus-positive human sera (Robinson et al., Lancet i:790-794, 1988; Robinson et al., J. Acq. Immun. Def. Synd. 2:33-42, 1989). These observations validate the macaque-SIV model for studies of C'-ADE.

Animals↗
PubMed1990

Simian immunodeficiency viruses from African green monkeys display unusual genetic diversity.

African green monkeys are asymptomatic carriers of simian immunodeficiency viruses (SIV), commonly called SIVagm. As many as 50% of African green monkeys in the wild may be SIV seropositive. This high seroprevalence rate and the potential for genetic variation of lentiviruses suggested to us that African green monkeys may harbor widely differing genotypes of SIVagm. To investigate this hypothesis, we determined the entire nucleotide sequence of an infectious proviral molecular clone of SIVagm (155-4) and partial sequences (long terminal repeat and Gag) of three other distinct SIVagm isolates (90, gri-1, and ver-1). Comparisons among the SIVagm isolates revealed extreme diversity at the nucleotide and amino acid levels. Long terminal repeat nucleotide sequences varied up to 35% and Gag protein sequences varied up to 30%. The variability among SIVagm isolates exceeded the variability among any other group of primate lentiviruses. Our data suggest that SIVagm has been in the African green monkey population for a long time and may be the oldest primate lentivirus group in existence.

Amino Acids↗
PubMed1990

Detection of SIV antigens by HIV-1 antigen capture immunoassays.

We tested three commercially available HIV-1 antigen capture systems for their ability to detect simian immunodeficiency viruses (SIV). All three kits detected antigens from six distinct SIV isolates, but with varying degrees of sensitivity. For the overall detection of SIV in cell culture, our assay for reverse transcriptase was more sensitive than HIV-1 antigen capture. HIV-1 antigen capture systems were useful for the detection of SIV antigenemia in experimentally infected macaques. The limited sensitivity of HIV-1-specific antigen capture suggests that SIV-specific antigen capture reagents should be developed.

Animals↗
PubMed1990

Molecular clones of SIVsm and SIVagm: experimental infection of macaques and African green monkeys.

We have investigated the ability of biologically-active proviral molecular clones of SIVsm and SIVagm to infect rhesus macaques, pig-tail macaques, and African green monkeys. Two clones of SIVsm were individually inoculated into four rhesus and four pig-tail macaques. All eight macaques became infected, and two have experienced a significant decline in absolute numbers of circulating CD4+ cells. None of three African green monkeys were infected by an SIVsm molecular clone. However, one of four African green monkeys did become infected by SIVsm after receiving lymphocytes directly from an SIVsm-infected rhesus macaque. A molecular clone of SIVagm infected three of four macaques and three of three African green monkeys. None of the three infected macaques had a significant decline in circulating CD4+ cells. Interestingly, infection of pig-tail macaques (but not rhesus macaques) with uncloned SIVagm induced a significant drop in circulating CD4+ cells. These data suggest that molecular clones of SIVsm and SIVagm can be used in experimental models of AIDS for the evaluation of viral gene functions and for the study of in vivo genetic variation.

Acquired Immunodeficiency Syndrome↗
PubMed1990

The simian immunodeficiency virus (SIV) rev gene regulates env expression.

The rev gene product is a trans-acting nuclear regulatory protein that is essential for AIDS virus replication. To define the effect of the SIV rev gene on its gp160 expression, two SV40 constructs have been made: pBC17 is a rev+env+ construct, and pBD21 is a rev-env+ construct. After transfecting the constructs into COS-1 cells, RNA, protein, syncytium formation, and monoclonal antibody blocking assays were performed. The results indicated that the SIV rev gene positively influenced the level of full-length env mRNA and was required for expression of SIV gp160.

Antibodies, Monoclonal↗
PubMed1990

Antibody-dependent enhancement of SIV infection: further characterization and cross reactivity between macaque and sooty mangabey isolates.

Plasma from four rhesus macaques (Macaca mulatta), of which two were experimentally infected with the simian immunodeficiency virus (SIV) isolate SIVmac251, one with isolate SIVsmF236, and another with a SIVsmF236 molecular clone, SIVsmH-4, enhanced SIVmac infection of MT-2 cells. In addition to SIV-positive plasma, infection-enhancement required complement, CD4, and CR2. Titers of infection-enhancing antibodies appeared to correlate with disease progression. The MT-2/SIVmac251 system should be useful in future studies of complement-mediated, antibody-dependent enhancement of macaque and sooty mangabey SIV isolates.

Animals↗
PubMed1990

Molecular characterization of SIV in tissues from experimentally infected macaques.

Tissues from SIV-infected, immunodeficient macaques were analyzed by southern blot and polymerase chain reaction (PCR) amplification of env sequences. Provirus was readily detected in both lymphoid and non-lymphoid tissues by southern blot analysis. The majority of virus was in an unintegrated state. Analysis of envelope sequences by PCR revealed that tissues contain many distinct, but closely related genotypes; however, only a subset of these proviral genomes are recovered after tissue culture passage in human cell lines. Thus, tissue culture isolates of SIV do not represent the complete spectrum of genotypes in an infected macaque.

Animals↗
PubMed1990

Molecular characterization of simian lentiviruses from east African green monkeys.

Asymptomatic infection with simian lentiviruses (also called simian immunodeficiency viruses, or SIV) is common among feral African green monkeys. To characterize the range of SIV genetic diversity among infected African green monkeys, we have determined nucleotide sequences from complete or partial molecular clones of four distinct SIVagm isolates from Kenya and Ethiopia. The nucleotide and amino acid variability we observed among the SIVagm isolates was greater than the variability within any other group of primate lentiviruses. These data suggest that: a) African green monkeys have been infected with simian lentiviruses for many years; and b) novel and uncharacterized primate lentiviruses may exist in the feral African green monkey population in other parts of Africa.

Amino Acid Sequence↗