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Molecular cloning and cell-specific growth characterization of polymorphic variants of type D serogroup 2 simian
G H Marracci1, N A Avery, S M Shiigi
1Department of Molecular Microbiology and Immunology, Oregon Health Sciences University, Portland, Oregon, 97201, USA.
Abstract:
Simian retroviruses (SRVs), the etiological agent of a spontaneous Simian acquired immunodeficiency syndrome, endemically infects large percentages of Asian macaques housed in biomedical research colonies and severely compromises the effective use of these species as a viable research animal. We recently described the molecular cloning of a serogroup 2 SRV, D2/RHE/OR, which causes mild immunosuppression in rhesus macaques. A restriction site variant, D2/RHE/OR/V1, has also been recovered from severely ill animals endemically infected with D2/RHE/OR. We now report the complete nucleotide sequences of D2/RHE/OR and D2/RHE/OR/V1. Both infectious molecular clones retain the genetic structure typical of type D SRVs (5' LTR-gag-prt-pol-env-3'LTR) and encode identically sized 8105-bp proviruses. D2/RHE/OR and D2/RHE/OR/V1 are 99.3% similar at the amino acid level, exhibiting only 17 residue differences, of which 10 are located in the envelope glycoproteins. The molecular clones and reciprocal chimeric viruses were used to assess the contribution of different genetic domains to virus infectivity in a T cell infection assay. These experiments indicate that D2/RHE/OR has a reduced ability to infect specific T cell lines, especially Hut-78 and MT-4 cells, and that the envelope gene is not the sole determinant of in vitro tropism.
Insights
Simian retroviruses (SRVs) cause disease in macaques, impacting research. Sequencing two SRV variants revealed minor genetic differences, primarily in envelope glycoproteins, influencing T cell infectivity.
Area of Science:
- Virology
- Immunology
- Primatology
Background:
- Simian retroviruses (SRVs) are endemic in research macaques, causing Simian acquired immunodeficiency syndrome and hindering research.
- A specific serogroup 2 SRV, D2/RHE/OR, causes mild immunosuppression, with a variant (D2/RHE/OR/V1) found in severely ill animals.
Purpose of the Study:
- To determine the complete nucleotide sequences of D2/RHE/OR and its variant D2/RHE/OR/V1.
- To analyze the genetic differences between the two SRV variants.
- To investigate the contribution of genetic domains to SRV infectivity and tropism in T cells.
Main Methods:
- Molecular cloning of SRV serogroup 2 strains.
- Complete nucleotide sequencing of SRV proviruses.
- Construction and testing of chimeric viruses in T cell infection assays.
Main Results:
- Both D2/RHE/OR and D2/RHE/OR/V1 share the typical type D SRV genetic structure and proviral size (8105 bp).
- The variants are highly similar (99.3% amino acid identity), with 17 residue differences, 10 in envelope glycoproteins.
- D2/RHE/OR demonstrated reduced infectivity in specific T cell lines (Hut-78, MT-4), indicating the envelope gene is not the sole determinant of in vitro tropism.
Conclusions:
- The genetic differences between D2/RHE/OR and D2/RHE/OR/V1 are minimal, despite clinical variations in infected animals.
- Viral envelope glycoproteins play a role, but are not solely responsible for the observed differences in T cell tropism.
- Further research is needed to understand the full determinants of SRV pathogenicity and tropism.