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Functional and immunological characterization of SIV envelope glycoprotein produced in genetically engineered
V Planelles1, N L Haigwood, M L Marthas
1Department of Medical Pathology, University of California, Davis 95616.
Abstract:
Retroviral envelope glycoproteins interact with cell receptors and are targets for antiviral immune responses in infected hosts. Macaque simian immunodeficiency virus (SIVmac) is a T-lymphocytopathic lentivirus which causes an AIDS-like disease in rhesus macaques. The envelope gene of SIVmac encodes a precursor glycoprotein (gp160) which is cleaved into an external domain (gp130) and a transmembrane domain (gp32). To investigate the functional and immunological properties of the SIV external envelope glycoprotein, we have used genetically engineered mammalian cells to produce recombinant gp130 (rgp130). The rgp130 has the appropriate molecular weight, is glycosylated, and has native conformation as determined by binding to the cell receptor for SIV, the CD4 antigen. Rhesus macaques immunized with purified rgp130 formulated in muramyl dipeptide adjuvant generated high titers of antienvelope antibodies. Antibodies from these macaques were tested for in vitro virus neutralization; very low or undetectable levels of neutralization were observed. In contrast, neutralizing antibodies were readily detected in sera from goats immunized with rgp130. With respect to cell-mediated immunity, proliferative responses to rgp130 were demonstrated in peripheral blood monocyte cells (PBMC) from macaques immunized with the recombinant glycoprotein as well as in PBMC from SIV-infected animals. These results show that rgp130 is functional and immunogenic; the potential of rgp130 for protective immunization remains to be determined.
Insights
Recombinant simian immunodeficiency virus (SIV) envelope glycoprotein (rgp130) is functional and elicits antibodies in macaques and goats. While macaques produced anti-envelope antibodies, they showed limited virus neutralization, suggesting rgp130
Area of Science:
- Immunology
- Virology
- Biochemistry
Background:
- Retroviral envelope glycoproteins are crucial for viral entry and are targets for immune responses.
- Simian immunodeficiency virus (SIVmac) causes an AIDS-like illness in rhesus macaques.
- The SIVmac envelope precursor (gp160) is processed into external (gp130) and transmembrane (gp32) glycoproteins.
Purpose of the Study:
- To produce and characterize recombinant SIV external envelope glycoprotein (rgp130).
- To evaluate the immunogenicity and functional properties of rgp130 in rhesus macaques.
- To assess the potential of rgp130 for developing antiviral immunity.
Main Methods:
- Genetically engineered mammalian cells were used to produce recombinant gp130 (rgp130).
- rgp130 characterization included molecular weight, glycosylation, and CD4 receptor binding.
- Rhesus macaques and goats were immunized with rgp130; immune responses were assessed via antibody titers, in vitro neutralization assays, and peripheral blood monocyte cell (PBMC) proliferation.
Main Results:
- Produced rgp130 exhibited appropriate molecular weight, glycosylation, and native conformation by binding to the CD4 receptor.
- Macaques immunized with rgp130 generated high titers of anti-envelope antibodies but showed minimal in vitro virus neutralization.
- Goats immunized with rgp130 produced readily detectable neutralizing antibodies.
- PBMC from immunized macaques and SIV-infected animals demonstrated proliferative responses to rgp130.
Conclusions:
- Recombinant SIV gp130 is functional and immunogenic in macaques.
- The capacity of rgp130 to induce protective immunity against SIV requires further investigation.
- rgp130 elicits different antibody responses in macaques and goats, highlighting species-specific immune reactions.