280 Influence of V3 Charge in Conjunction with gp120 N-linked Glycosylation Patterns on Chemokine and Neutralizing Antibody Inhibition of HIV-1 A Nabatov, G Pollakis, T Linnemann, A Kliphuis, M Chalaby, W Paxton* Univ of Amsterdam, The Netherlands
Background: The HIV-1 gp120 envelope N-linked glycosylation pattern, in conjunction with V3 charge, has been shown to modify viral co-receptor usage. We wished to identify what influence these envelope characteristics and their combinations had on virus sensitivity to inhibition with CC/CXC-chemokines, dextran sulphate, sCD4, and envelope specific monoclonal antibodies.
Methods: We utilized a panel of molecular cloned viruses variant with respect to their V3 charge, V1V2 region and their V1 and V3 N-linked glycosylation patterns. The viruses were tested in CD4+ lymphocyte infection assays in the presence of RANTES, SDF-1alpha, EOTAXIN, dextran sulphate, sCD4, 2F5, IgG1b12, 2G12.
Results: We studied viruses that ranged in their co-receptor phenotype from R5 through R3/R5/X4 "intermediate" to X4. Alterations in the V3 charge alone could modify virus sensitivity to inhibition with CC- and CXC-chemokines with the higher V3 charges being associated with a greater sensitivity to RANTES and lower sensitivity to SDF-1alpha inhibition. At higher V3 charges SDF-1alpha inhibition was influenced by the N-linked glycosylation pattern of the envelope. Dual-tropic viruses lost their sensitivity to RANTES but not SDF-1alpha and demonstrated growth enhancement in the presence of EOTAXIN. Viruses with higher V3 charges were more sensitive to inhibition with dextran sulfate and were not influenced by N-linked glycosylation differences. Neutralization with sCD4 demonstrated that dual-tropic "intermediate" viruses altering in N-linked glycosylation patterns possessed a lower sensitivity to blocking in comparison to either R5 or X4 viruses and that this was consistent irrespective of V3 charge. The same observation was seen for blocking with the 2G12 monoclonal antibody. However, the IgG1b12 monoclonal antibody showed a reversed profile with the "intermediate" viruses demonstrating an increase in resistance over the early and late viruses.
Conclusions: We conclude that alterations in V3 charge and gp120 N-linked glycosylation patterns can greatly modify the extent to which a virus can be inhibited by CC/CXC chemokines and neutralizing antibodies. The results indicate that "intermediate" dual-tropic viruses have an increased affinity to CD4 in comparison to the R5 or X4 viruses suggesting that when switching from the R5 to X4 phenotype the envelope takes on a more open molecular structure that may alter the viruses susceptibility to control by antibody neutralizing responses.
