Antiviral Activities of HIV-1-Specific Human Broadly Neutralizing Antibodies Are Isotype-Dependent

Abstract

Broadly neutralizing antibodies (bNAbs) offer promising opportunities for preventing HIV-1 infection. The protection mechanisms of bNAbs involve the Fc domain, as well as their Fab counterpart. Here, different bNAb isotypes including IgG1, IgA1, IgA2, and IgA122 (IgA2 with the hinge of IgA1) were generated and then produced in CHO cells. Their ability to neutralize pseudovirus and primary HIV-1 isolates were measured, as well as their potential ADCC-like activity using a newly developed assay. In our work, gp41-specific IgA seems to be more efficient than IgG1 in inducing ADCC-like activity, but not in its virus neutralization effect. We show that either gp120-specific IgA or IgG1 isotypes are both efficient in neutralizing different viral strains. In contrast, gp120-specific IgG1 was a better ADCC-like inducer than IgA isotypes. These results provide new insights into the neutralization and ADCC-like activity of different bNAbs that might be taken into consideration when searching for new treatments or antibody-based vaccines.

Keywords: ADCC; HIV; broadly neutralizing antibodies; gp120; gp41; neutralization.

Figure 1

Characterization of the different bNAb isotypes: (a) Separation of bNAbs IgG and (b) IgA isotypes on SDS-PAGE (Bis-Tris 4–12%). An amount of 10 µg of the corresponding antibody was loaded on the gel. The first and last lanes of each gel correspond to the molecular weight marker. Two IgA controls were used: colostrum IgA and a highly purified IgA. Migration was performed at 150 V for 1 h.

Figure 2

ADCC-like activities of bNAbs depend on their isotypes and their specificity: (a) %ADCC for each evaluated concentration. Each point represents the mean and SEM of triplicates from two different experiments. Student’s t-test was used for antibodies PGT145, PG16, 10E8, PGT126, PGT128, and NIH4546. A 2-way ANOVA with Tukey’s multiple comparisons was used for the antibodies 2F5 and B12. * p < 0.05, ** p < 0.01, *** p < 0.001 (b) Heatmap of EC50 (µg/mL) values obtained for ADCC. Numbers indicate the geometric mean values of results from triplicates of at least two independent experiments (n = 6).

Figure 3

Neutralizing activity of bNAbs depend also on their isotypes and their specificity. Heatmap of EC50 (µg/mL) values obtained for neutralization for all tested antibodies using: (a) TZM-bl cells and pseudovirus or (b) PBMCs isolated from healthy donors and primary isolates. Numbers indicate the geometric mean values of results from duplicates of at least two independent experiments (n = 4). A 2-way ANOVA with Tukey’s multiple comparisons was used to compare EC50s from all the antibodies per virus.

Figure 4

Correlation between: (a) MFI and ADCC-like EC50, (b) ADCC-like EC50 and Neutralization EC50. Each point represents the mean value of triplicates from two different experiments (n = 6). Non-parametric Spearman correlation was calculated for each case.