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121 Effects of Glycosylation Variation on Envelope-Specific Antibody Responses
K. S. Cole*1, J. D. Steckbeck 1, J. L. Rowles1, R. C. Desrosiers2, and R. C. Montelaro1
1Univ. of Pittsburgh Sch. of Med., PA, USA and 2New England Regional Primate Res. Ctr., Southborough, MA, USA
Background: Carbohydrates present on SIV and HIV envelope proteins serve to shield the virus from immune recognition. In the present study, we analyzed the effects of N-linked glycosylation sites in and around the V1 and V2 regions of SIVmac239 gp120 on antibody maturation to native envelope proteins and antibody recognition of defined linear and conformational envelope domains.
Methods: Longitudinal plasma samples from rhesus macaques experimentally infected with SIVmac239 viruses with abrogated N-linked glycosylation sites in and around the V1 and V2 regions of gp120 were analyzed for quantitative and qualitative antibody properties by ELISA. Antigens used for these studies included SIV envelope proteins (gp120 and gp41) captured directly from detergent-disrupted virus, synthetic peptides representing defined linear determinants of SIV gp120, and chimeric envelope proteins representing conformational domains of SIV gp120 in an HIV-1 envelope backbone.
Results: Infection of rhesus macaques with SIVmac239 viruses containing double (g45, g46, and g56) or combination (g4,5,8,12,13) deletions of N-linked glycosylation sites in and around the V1 and V2 regions of gp120 resulted in altered antibody maturation. In particular, removal of the g4 site located in V1 resulted in significantly enhanced recognition of both linear and conformational epitopes in V1 as well as enhanced recognition of the cysteine loop (analogous to the V3 region in HIV-1 gp120) when compared with control monkeys infected with virus containing fully glycosylated envelope proteins.
Conclusions: Removal of N-linked glycosylation sites in the V1 region resulted in increased reactivity to both the V1 and the cysteine loop/V3 regions of SIV gp120 in vivo, demonstrating that carbohydrates present on SIV gp120 serve to shield the virus from humoral immune recognition. Identification of additional N-linked glycosylation sites, alone or in combination, that limit the humoral immune response to SIV gp120 will be useful in redirecting and eliciting effective virus-specific immune responses, an important consideration in future vaccine studies.
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