Polyfunctional HIV-Specific Antibody Responses Are Associated with Spontaneous HIV Control

Abstract

Elite controllers (ECs) represent a unique model of a functional cure for HIV-1 infection as these individuals develop HIV-specific immunity able to persistently suppress viremia. Because accumulating evidence suggests that HIV controllers generate antibodies with enhanced capacity to drive antibody-dependent cellular cytotoxicity (ADCC) that may contribute to viral containment, we profiled an array of extra-neutralizing antibody effector functions across HIV-infected populations with varying degrees of viral control to define the characteristics of antibodies associated with spontaneous control. While neither the overall magnitude of antibody titer nor individual effector functions were increased in ECs, a more functionally coordinated innate immune-recruiting response was observed. Specifically, ECs demonstrated polyfunctional humoral immune responses able to coordinately recruit ADCC, other NK functions, monocyte and neutrophil phagocytosis, and complement. This functionally coordinated response was associated with qualitatively superior IgG3/IgG1 responses, whereas HIV-specific IgG2/IgG4 responses, prevalent among viremic subjects, were associated with poorer overall antibody activity. Rather than linking viral control to any single activity, this study highlights the critical nature of functionally coordinated antibodies in HIV control and associates this polyfunctionality with preferential induction of potent antibody subclasses, supporting coordinated antibody activity as a goal in strategies directed at an HIV-1 functional cure.

Fig 1. Elite controllers exhibit polyfunctional antibody effector activity profiles in the absence of enhanced antibody responses in individual effector functions.

A-G. Purified plasma IgG from elite controllers (EC), viremic controllers (VC), infected subjects on therapy (CT), and infected subjects off therapy (CU) were evaluated for their ability to drive NK-dependent ADCC against rgp120-pulsed CD4+ target cells (A), monocyte-directed phagocytosis of rgp120-functionalized fluorescent beads (B), complement deposition (C3b) on the surface of rgp120-pulsed CD4+ target cells (C), neutrophil-directed phagocytosis (D), and induce surface expression or production of CD107a (E), IFN-γ (F), and MIP-1β (G) by NK cells in the presence of rgp120-pulsed plates. Differences between subject groups were evaluated using ANOVA adjusted for multiple comparisons using Tukey’s Test in Graphpad Prism.

Fig 2. Functional coordination within HIV-infected subject groups.

A. The extent of functional coordination within groups was assessed by calculating Spearman’s rank correlation coefficients across each pair of independently assessed functional assays. Differences between subject groups were evaluated using a Friedman ANOVA corrected for multiple comparisons using Dunn’s Test in Graphpad Prism. B. Prevalence of functional correlations by strength for each subject group. C. Correlation matrix for each pairwise combination of functions tested, in which strong positive correlations appear blue while inverse correlations appear red, for each subject group. Correlative relationships and significance were calculated and visualized using R, with unadjusted p values indicated to facilitate relative comparisons.

Fig 3. Levels and IgG subclass composition differentiate HIV+ subject groups.

A. Titer (Mean Fluorescent Intensity, MFI) of gp120-specific IgG present in each subject group. B. The percent of subjects in each group positive for gp120-specific responses of each IgG subclass. C. Spearman correlation matrix between subclass responses across subjects. Strength and significance, as calculated in Graphpad Prism, are represented as color intensity and size, respectively. D. The levels of gp120-specific responses observed across cohort groups for each IgG subclass. Differences between groups were assessed by Kruskal-Wallis ANOVA and corrected for multiple comparisons using Dunn’s test in Graphpad Prism.

Fig 4. Antibody functionality can be predicted by subclass composition.

A. Correlative relationships between levels of total gp120-specific IgG or gp120-specific antibodies of each subclass to antibody function were assessed by determination of Spearman’s rank correlation coefficients between activity and antibody MFI within each subject group. B. Correlative relationships between relative levels of gp120-specific antibodies of each subclass (i.e., MFI of subclass/MFI of total IgG) were assessed for each functional activity, over all subjects. Positive associations are noted in blue and inverse associations in red, with the magnitude of correlation depicted by intensity. Correlative relationships and significance were calculated and visualized using R, with unadjusted p values indicated to facilitate relative comparisons. C. The magnitude and direction of the contribution of SF162-specific antibody subclass assessments to cross-validated predictive models of polyfunctional activity.