Resistance to V3-directed neutralization caused by an N-linked oligosaccharide depends on the quaternary structure of the HIV-1 envelope oligomer.
A conserved N-glycan present within the V3 loop of gp120 modulates the sensitivity to neutralization by antibodies directed to the V3 loop. A glycan-deficient mutant of HIVLAI, designated HIVA308, displayed a 100-fold increase in sensitivity to neutralization by anti-V3 MAb NEA-9205 compared to wild-type HIVLAI. This difference in sensitivity was not caused by an alteration of the antibody binding site itself, as NEA-9205 had equal affinity for both wild-type and mutant monomeric gp120. In contrast, virion-associated wild-type gp120 was immunoprecipitated less efficiently with NEA-9205 than virion-associated mutant gp120. This difference was completely abrogated, if immunoprecipitation were carried out in the presence of detergent. Furthermore, treatment of virion preparations with detergent exposed the C-terminal D7324 epitope, which is inaccessible on virion-associated gp120 but readily accessible on monomeric, soluble gp120. Finally, both wild-type and mutant monomeric, soluble gp120 were precipitated equally efficiently by NEA-9205 in the absence of detergent. Thus, the NEA-9205 epitope was readily accessible on monomeric gp120 regardless of the presence of the 306N-glycan, and inaccessibility of the NEA-9205 epitope imparted by the 306N-glycan was observed only on the intact envelope oligomer.
Schønning
K
K
Laboratory of Infectious Diseases, Hvidovre Hospital, 2650, Denmark.
Jansson
B
B
Olofsson
S
S
Nielsen
J O
JO
Hansen
J S
JS
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology; D002460:Cell Line; D000939:Epitopes / Q000276:immunology; D015483:HIV Antibodies / Q000276:immunology*; D015699:HIV Envelope Protein gp120 / Q000737:chemistry / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D051379:Mice; D009500:Neutralization Tests; D010446:Peptide Fragments / Q000737:chemistry / Q000276:immunology*; D011134:Polysaccharides / Q000276:immunology*; D011487:Protein Conformation
D000911:Antibodies, Monoclonal; D000939:Epitopes; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; C059762:HIV envelope protein gp120 (305-321); D010446:Peptide Fragments; D011134:Polysaccharides