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The simian immunodeficiency virus envelope open reading frame located after the termination codon is expressed in
G Franchini1, P J Kanki, M L Bosch
1Laboratory of Tumor Cell Biology, National Cancer Institute, Bethesda, MD 20892.
Abstract:
Genetic comparison of SIVmac to the human retroviruses generally associated with AIDS revealed a closer relationship to HIV-2 than to HIV-1. A common feature differentiating SIV and HIV-2 from HIV-1 is the size of the transmembrane portion of the envelope, which is smaller (gp32) in SIVmac and HIV-2 than in HIV-1 (gp41). The presence of this truncated form of the transmembrane glycoprotein in SIVmac and HIV-2 virions is apparently related to the presence of a translation termination codon in the env gene of all SIV proviruses analyzed as well as in one HIV-2 provirus. Since the carboxy terminus of the envelope transmembrane protein has been implicated in the cytopathic effect of HIV-1 in vitro, we decided to investigate whether putative expression of the open reading frame located after the termination codon correlates with the pathogenicity of SIVmac in vivo. We generated two synthetic peptides from the inferred amino acid sequence of SIVmac and tested their reactivity by Western blot against the sera of naturally and experimentally infected monkeys as well as against sera of HIV-2-infected individuals. Our results indicate that the protein synthesized from this open reading frame is expressed in vivo, since an immunoresponse can be detected against the synthetic peptides in two of three experimentally SIVmac-infected animals. However, no correlation can be found between its expression and disease progression at this time. Furthermore, a rabbit immune serum raised against the synthetic peptide failed to identify any specific protein in SIVmac-infected cells.
Insights
Simian immunodeficiency virus (SIVmac) shares traits with human immunodeficiency virus type 2 (HIV-2). A novel SIVmac protein is expressed in vivo, but its role in disease progression remains unclear.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Simian immunodeficiency virus (SIVmac) is genetically related to human immunodeficiency virus type 2 (HIV-2), differing from HIV-1 in envelope protein structure.
- SIVmac and HIV-2 possess a smaller transmembrane envelope glycoprotein (gp32) compared to HIV-1 (gp41), linked to a translation termination codon in the env gene.
- The carboxy terminus of HIV-1's envelope transmembrane protein is associated with in vitro cytopathic effects, prompting investigation into SIVmac's analogous protein.
Purpose of the Study:
- To investigate the in vivo expression of a potential protein encoded by an open reading frame following a termination codon in the SIVmac env gene.
- To determine if this SIVmac protein expression correlates with the pathogenicity of SIVmac infection in vivo.
- To analyze the immune response against this putative SIVmac protein in infected animals and individuals.
Main Methods:
- Generated two synthetic peptides based on the inferred amino acid sequence of the SIVmac open reading frame.
- Tested peptide reactivity using Western blot against sera from naturally and experimentally SIVmac-infected monkeys, and HIV-2-infected individuals.
- Used rabbit immune serum against the synthetic peptide to detect specific proteins in SIVmac-infected cells.
Main Results:
- An immune response against the synthetic peptides was detected in two of three experimentally SIVmac-infected animals, indicating in vivo expression of the protein.
- No correlation was found between the expression of this protein and disease progression in the studied animals.
- A rabbit antiserum raised against the synthetic peptide did not identify any specific protein in SIVmac-infected cells.
Conclusions:
- The study provides evidence for the in vivo expression of a novel SIVmac protein.
- The role of this expressed protein in the pathogenesis of SIVmac infection requires further investigation.
- Current findings do not establish a link between this protein's expression and disease progression.