PubMed · 10635861
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N Handa. 1999. [Human immunodeficiency virus type 1, type 2].. https://pubmed.ncbi.nlm.nih.gov/10635861/
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Here we report that N-glycans within the V1/V2 variable regions of the NL4-3 gp120 glycoprotein are indispensable to maintain viral functionality and are masking neutralizing epitopes. Fifteen variants of HIV-1 isolate NL4-3 with mutations of the six N-glycosylation sites g2-g7 within the V1 (g2-g4) and V2 loop (g5-g7) of gp120 were analyzed for viral infectivity and their sensitivity to neutralization. Presence of the N-glycans g4, g5, g6 and g7 was an important prerequisite to maintain viral infectivity, since virus mutants lacking these N-glycans were highly deficient in virus entry. Lack of g4 or g7 correlated to a reduction of infectivity to less than 3% of the infectivity observed for NL4-3 wild type. In contrast, mutants lacking N-glycans g2 and g3 showed a 50% increase in infectivity compared to NL4-3. Mutants lacking g2, g3, g5 and g6 with an infectivity of more than 10% of the NL4-3 wt virus were tested for neutralization and showed a high sensitivity against human serum antibody from HIV-1 infected individuals.
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Recombinant lentiviral vectors pseudotyped with heterologous HIV-1 envelope glycoproteins allow rapid and accurate measurement of antibody-mediated HIV-1 neutralization. However, the neutralization phenotypes of envelope pseudoviruses have not been directly compared to isogenic replication competent HIV-1. We produced pseudoviruses expressing three different HIV-1 envelope glycoproteins and subcloned the same three env genes into a replication competent NL4-3 molecular clone. For each of the antibodies tested, the neutralization dose-response curves of pseudoviruses and corresponding replication competent viruses were similar. Thus, envelope pseudoviruses can be used to study the anti-HIV-1 neutralizing antibody response. A single passage of replication competent virus derived from 293T cells through peripheral blood mononuclear cells (PBMC) caused a substantial decrease in sensitivity to neutralizing antibodies. This was associated with an increase in average virion envelope glycoprotein content of the PBMC-derived virus. Replication competent HIV-1 and isogenic envelope pseudoviruses have similar neutralization characteristics, but passage into PBMC is associated with decreased sensitivity to neutralization.