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Simian immunodeficiency virus (mac 251-32H) transmembrane protein sequence remains conserved throughout the course of
1National Institute for Biological Standards and Control, Potters Bar, Herts, UK.
Abstract:
Two cynomolgus macaques were infected with a genetically complex challenge stock of simian immunodeficiency virus (SIVmac251-32H). The polymerase chain reaction (PCR) was used to amplify the env gp41, rev, and nef overlapping coding sequences from provirus present in the blood of both animals at 1, 6, and 15 months post infection (p.i.). The predominant, env sequences found in both animals at the three time points were very similar to that found in the original 11/88 challenge stock. The functionally important hydrophobic fusion and membrane-spanning domains within gp41 remained conserved throughout the course of infection. Nucleotide variation within the region corresponding to the REV response element (RRE) was limited to four positions, none of which were predicted to cause any significant disruption to the secondary structure of the RRE. Very little genetic variation was observed in and around the cluster of potential glycosylation sites of the external portion of gp41. However, the existence of a previously assigned variable region elsewhere in the cytoplasmic domain of gp41 was confirmed. The three gene loci (env, rev, and nef) examined varied independently. All changes in the predominant protein sequences were brought about by single nucleotide substitutions only. After 15 months of infection with SIV, 1 animal was sick from SIV-induced disease whereas the other remained healthy. In-frame stop codons within the transmembrane protein occurred with a much greater frequency in the healthy animal.
Insights
Simian immunodeficiency virus (SIV) env, rev, and nef gene sequences showed limited variation in macaques post-infection. Healthy animals had more stop codons in the SIV transmembrane protein, suggesting a role in disease outcome.
Area of Science:
- Virology
- Molecular Biology
- Immunology
Background:
- Simian immunodeficiency virus (SIV) infection in macaques serves as a model for human immunodeficiency virus (HIV) research.
- Understanding viral genetic evolution during infection is crucial for developing effective interventions.
Purpose of the Study:
- To analyze the genetic variation of SIV env, rev, and nef genes in cynomolgus macaques post-infection.
- To investigate the correlation between viral genetic changes and disease progression.
Main Methods:
- Cynomolgus macaques were infected with SIVmac251-32H.
- Polymerase chain reaction (PCR) was used to amplify viral gene sequences (env gp41, rev, nef) at 1, 6, and 15 months post-infection.
- Sequence analysis focused on conserved domains, potential glycosylation sites, and variable regions.
Main Results:
- Predominant env sequences remained similar to the original challenge stock.
- Functional domains of gp41 and the REV response element (RRE) showed limited variation.
- Independent variation was observed across env, rev, and nef loci, primarily through single nucleotide substitutions.
- Healthy animals exhibited a higher frequency of in-frame stop codons in the transmembrane protein compared to the sick animal.
Conclusions:
- SIV env, rev, and nef genes exhibit remarkable genetic stability in key functional regions during chronic infection.
- Viral genetic variation occurs independently across these loci.
- The increased frequency of stop codons in the transmembrane protein of healthy macaques suggests a potential protective mechanism or a marker of attenuated disease.