Multiple Interactions across the Surface of the gp120 Core Structure Determine the Global Neutralization Resistance Phenotype of Human Immunodeficiency Virus Type 1

Abstract

Resistance to neutralization is an important characteristic of primary isolates of human immunodeficiency virus type 1 (HIV-1) that relates to the potential for successful vaccination to prevent infection and use of immunotherapeutics for treatment of established infection. In order to further elucidate mechanisms responsible for neutralization resistance, we studied the molecular mechanisms that determine the resistance of the primary virus isolate of the strain HIV-1 MN to neutralization by soluble CD4 (sCD4). As is the case for the global neutralization resistance phenotype, sCD4 resistance depended upon sequences in the amino-terminal heptad repeat region of gp41 (HR1), as well as on multiple functional interactions within the envelope complex. The functional interactions that determined the resistance included interactions between the variable loop 1 and 2 (V1/V2) region and sequences in or near the CD4 binding site (CD4bs) and with the V3 loop. Additionally, the V3 loop region was found to interact functionally with sequences in the outer domain of gp120, distant from the CD4bs and coreceptor-binding site, as well as with a residue thought to be located centrally in the coreceptor-binding site. These and previous results provide the basis for a model by which functional signals that determine the neutralization resistance, high-infectivity phenotype depend upon interactions occurring across the surface of the gp120 core structure and involving variable loop structures and gp41. This model should be useful in efforts to define epitopes that may be important for primary virus neutralization.Resistance to antibody-mediated neutralization of infectivity is characteristic of naturally occurring strains of human immunodeficiency virus type 1 (HIV-1) that have not been manipulated in the laboratory (15, 18). Such strains are commonly referred to as primary isolates. This property is a limiting factor with respect to efforts to develop a vaccine that may protect by induction of potent neutralizing antibodies. Induction of potent neutralizing antibodies is a common property of successful viral vaccines (26). Insights into the mechanisms of neutralization resistance of primary isolates of HIV-1 may indicate possible approaches to neutralization of such viruses and facilitate vaccine development.Our laboratory has previously reported studies of the MN strain of HIV-1 that have begun to address this issue (14,(21)(22)(23). The original isolate of the MN virus was propagated in a continuous T-cell line and is considered T-cell line adapted (TCLA) (12, 30). It is unusual among both primary and TCLA strains of HIV-1 in its high sensitivity to neutralization by antibodies in sera of infected patients and monoclonal antibodies (MAbs) against multiple linear and conformation-sensitive epitopes on the envelope glycoproteins (4,7,40,48). In an early study a neutralization-resistant variant of this strain was studied that was produced by growth of the MN strain virus in the presence of a highly neutralizing human serum (22). T...

Improved Breadth and Potency of an HIV-1-Neutralizing Human Single-chain Antibody by Random Mutagenesis and Sequential Antigen Panning

“…In both assays, m9 exhibited the highest potency, with IC 90 s ranging from 4 mg/ml to 25 mg/ml, which was, on average, two-to threefold lower than the IC 90 for scFv X5; the inhibitory activity of m6 was, on average, comparable to that of scFv X5 in these assays ( Table 1). Note that for all tested isolates in the PBMC assay, scFv X5 exhibited higher potency than Fab X5 and IgG1 X5 as has been demonstrated recently for other isolates; 12 further, we will compare only scFv X5 with m6 and m9.…”

Intrapatient Alterations in the Human Immunodeficiency Virus Type 1 gp120 V1V2 and V3 Regions Differentially Modulate Coreceptor Usage, Virus Inhibition by CC/CXC Chemokines, Soluble CD4, and the b12 and 2G12 Monoclonal Antibodies

“…It is of interest that the V1V2 and V3 changes we examined did not overlap any of the binding sites of the MAbs studied. A likely explanation is therefore conformational changes within the MAb binding sites (including CD4BS) induced by the V1V2 and V3 changes, similar to what has been previously shown (5). Another explanation is that modified V1V2 and V3 can interact with residues that are close to these binding sites and that modify antibody recognition.…”

Impact of V2 Mutations on Escape from a Potent Neutralizing Anti-V3 Monoclonal Antibody during In Vitro Selection of a Primary Human Immunodeficiency Virus Type 1 Isolate

“…Substitutions at residues 165 to 167 during the adaptation of various HIV-1 strains to replication in vitro have been reported; the adaptation is associated with an increase of the positive charge of this amino acid motif (1,13,39,52,57,63). In our present study, the amino acid change at 166/167 in the V2 region in passaged MOKW viruses with KD-247 was RD to KN, again increasing the positive charge.…”