Human Anti-HIV-1 GP120 monoclonal antibody, clone IHO205

In clinical trials, HIV-1 broadly neutralizing antibodies (bnAbs) effectively lower plasma viremia and delay virus reemergence. The presence of less neutralization-susceptible strains prior to treatment decreases the efficacy of these antibody-based treatments, but neutralization sensitivity often cannot be predicted by sequence analysis alone. We found that phenotypically confirmed CXCR4-utilizing strains are less neutralization sensitive, especially to variable loop 3 (V3 loop)-directed bnAbs, than exclusively CCR5-utilizing strains in some, but not all, cases. Homology modeling suggested that the primary V3 loop bnAb epitope is equally accessible among CCR5- and CXCR4-using strains, although variants that exclusively use CXCR4 have V3 loop protrusions that interfere with CCR5 receptor interactions. Homology modeling also showed that among some, but not all, envelopes with decreased neutralization sensitivity, V1 loop orientation interfered with V3 loop-directed bnAb binding. Thus, there are likely different structural reasons for the coreceptor usage restriction and the different bnAb susceptibilities. Importantly, we show that individuals harboring envelopes with higher likelihood of using CXCR4 or greater predicted V1 loop interference have faster virus rebound and a lower maximum decrease in plasma viremia, respectively, after treatment with a V3 loop bnAb. Knowledge of receptor usage and homology models may be useful in developing future algorithms that predict treatment efficacy with V3 loop bnAbs. IMPORTANCE The efficacy of HIV-1 broadly neutralizing antibody (bnAb) therapies may be compromised by the preexistence of less susceptible variants. Sequence-based methods are needed to predict pretreatment variants neutralization sensitivities. HIV-1 strains that exclusively use the CXCR4 receptor rather than the CCR5 receptor are less neutralization susceptible, especially to variable loop 3 (V3 loop) bnAbs in some, but not all, instances. While the inability to utilize the CCR5 receptor maps to a predicted protrusion in the envelope V3 loop, this viral determinant does not directly influence V3 loop bnAb sensitivity. Homology modeling predicts that contact between the envelope V1 loop and the antibody impacts V3 loop bnAb susceptibility in some cases. Among pretreatment envelopes, increased probability of using CXCR4 and greater predicted V1 interference are associated with faster virus rebound and a smaller decrease in the plasma virus level, respectively, after V3 loop bnAb treatment. Receptor usage information and homology models may be useful for predicting V3 loop bnAb therapy efficacy.

Objectives: Complement C3d receptor 2 (CR2) is the main receptor for complement protein C3d and plays an important role in adaptive immune responses. CR2 genetic variants are associated with susceptibility to systemic lupus erythematosus as well as to HIV-1 infection. In addition, CR2 function can be subverted by HIV-1 for an efficient entry into target cells; in a process known as antibody-dependent enhancement of viral infection. We sought to determine the association betweenCR2gene variants with HIV-1 acquisition after vaccination with recombinant gp120 protein (Vax004 clinical trial). Design and methods: This is a retrospective cross-sectional study, comprising male volunteers of European ancestry including infected (n = 273) and uninfected (n = 402) vaccinees and placebo, who were genotyped for three single nucleotide polymorphisms (SNPs) in theCR2gene region. Results: An interaction was observed between the baseline sexual behavior and the SNP rs3813946 for higher risk of infection in vacinees (interaction termP = 0.02). This SNP was associated with increased susceptibility to HIV-1 infection after vaccination in volunteers with low behavioral risk odds ratio (95% confidence interval): 5.5 (1.4-21.7)P = 0.006 but not vaccinees with high behavioral risk or volunteers given placebo (P = 0.7). Moreover,CR2genotype was strongly associated with the rate of HIV-1 acquisition after vaccination in low-risk volunteers [hazard odds ratio (95% confidence interval): 3.3 (1.6-7.0),P = 0.001]. Conclusion: The current study suggests thatCR2may play a role in HIV-1 acquisition after vaccination with rgp120 proteins.