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Simian immunodeficiency virus from African green monkeys
1New England Regional Primate Research Center, Harvard Medical School, Southborough, Massachusetts 01772.
Abstract:
Simian immunodeficiency virus (SIV) was isolated from the total peripheral blood mononuclear cell population and the monocyte-macrophage adherent cell population of three seropositive green monkeys originating from Kenya. SIV from these African green monkeys (SIVagm) was isolated and continuously produced with the MOLT-4 clone 8 (M4C18) cell line but not with a variety of other cells including HUT-78, H9, CEM, MT-4, U937, and uncloned MOLT-4 cells. Once isolated, these SIVagm isolates were found to replicate efficiently in M4C18, SupT1, MT-4, U937, and Jurkat-T cells but much less efficiently if at all in HUT-78, H9, CEM, and MOLT-4 cells. The range of CD4+ cells fully permissive for replication of these SIVagm isolates thus differs markedly from that of previous SIV isolates from macaques (SIVmac). These SIVagm isolates had a morphogenesis and morphology like that of human immunodeficiency virus (HIV) and other SIV isolates. Antigens of SIVagm and SIVmac cross-reacted by comparative enzyme-linked immunosorbent assay only with reduced efficiency, and optimal results were obtained when homologous antibody and antigen were used. Western blotting (immunoblotting) of purified preparations of SIVagm isolate 385 (SIVagm385) revealed major viral proteins of 120, 27, and 16 kilodaltons (kDa). The presumed major core protein of 27 kDa cross-reacted antigenically with the corresponding proteins of SIVmac (28 kDa) and HIV-1 (24 kDa) by Western blotting. Hirt supernatant replicative-intermediate DNA prepared from cells freshly infected with SIVagm hybridized to SIVmac and HIV-2 DNA probes. Detection of cross-hybridizing DNA sequences, however, required very low stringency, and the restriction endonuclease fragmentation patterns of SIVagm were not similar to those of SIVmac and HIV-2. The nucleotide sequence of a portion of the pol gene of SIVagm385 revealed amino acid identities of 65% with SIVmac142, 64% with HIV-2ROD, and 56% with HIV-1BRU; SIVagm385 is thus related to but distinct from previously described primate lentiviruses SIVmac, HIV-1, and HIV-2. Precise information on the genetic makeup of these and other SIV isolates will possibly lead to better understanding of the history and evolution of these viruses and may provide insight into the origin of viruses that cause acquired immunodeficiency syndrome in humans.
Insights
New simian immunodeficiency virus (SIVagm) strains from African green monkeys were isolated and characterized. These SIVagm isolates exhibit distinct replication patterns and genetic makeup compared to other primate lentiviruses, offering insights into lentivirus evolution.
Area of Science:
- Virology
- Immunology
- Genetics
Background:
- Simian immunodeficiency virus (SIV) is a lentivirus that infects non-human primates.
- Understanding SIV diversity is crucial for insights into human immunodeficiency virus (HIV) evolution and pathogenesis.
- African green monkeys are a natural reservoir for SIV, known as SIVagm.
Purpose of the Study:
- To isolate and characterize novel SIVagm strains from Kenyan green monkeys.
- To determine the replication efficiency of these SIVagm isolates in various cell lines.
- To compare the genetic and antigenic properties of SIVagm with other primate lentiviruses like SIVmac and HIV.
Main Methods:
- Isolation of SIVagm from peripheral blood mononuclear cells and monocyte-macrophage populations.
- Continuous production and replication studies using cell lines (MOLT-4 clone 8, SupT1, MT-4, U937, Jurkat-T, HUT-78, H9, CEM).
- Antigenic cross-reactivity assessment using enzyme-linked immunosorbent assay and Western blotting.
- Viral DNA hybridization and nucleotide sequencing of the pol gene.
Main Results:
- SIVagm was successfully isolated and produced in the M4C18 cell line.
- SIVagm isolates replicated efficiently in specific CD4+ T-cell lines (M4C18, SupT1, MT-4, U937, Jurkat-T), differing from SIVmac.
- Antigenic cross-reactivity between SIVagm and SIVmac was reduced; major viral proteins identified.
- Nucleotide sequencing revealed SIVagm385 is related to but distinct from SIVmac, HIV-2, and HIV-1.
Conclusions:
- The isolated SIVagm strains possess unique replication characteristics and genetic profiles.
- These findings highlight the genetic diversity within SIVagm.
- Further genetic analysis of SIV isolates can enhance understanding of lentivirus evolution and the origins of HIV.