AN N-GLYCAN WITHIN THE HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 GP120 V3 LOOP AFFECTS VIRUS NEUTRALIZATION

Carbohydrate side chains of envelope glycoproteins of HIV-1 and other viruses have been postulated to interfere with binding of neutralizing antibodies. So far, however, little evidence for interference of specific N-glycans with virus neutralization has been provided. We used four infectious HIV-1 molecular clones chimeric for their gp120 vs domains to study the influence on HIV-1 neutralization of an N-glycan localized within the V3 loop. Two clones lacking the N-301-glycan were at least 8-fold more sensitive to neutralization by two V3-specific monoclonal antibodies (MAbs) and 2- to 10-fold more sensitive to neutralization by a CD4-binding-site-specific human MAb than two HIV-1 clones glycosylated at this site. The affinity of the vs MAbs for soluble gp120 of the four clones was similar. However, a decreased binding of these MAbs to the gp120 of the two N-301-glycosylated clones was observed when the majority of gp120 was virion-associated during the initial binding step. These findings indicate that the N-301-glycan may interfere with the binding of neutralizing antibodies by limiting the accessibility of neutralization sites or by inducing conformational changes in the HIV-1 gp120 molecule. (C) 1994 Academic Press, inc.