CD4 T cell counts are inversely correlated with anti-gp120 cluster A antibodies in antiretroviral therapy-treated PLWH

Abstract

Background: While antiretroviral therapy (ART) efficiently suppresses viral replication, inflammation and immune dysfunction persist in some people living with HIV-1 (PLWH). HIV-1 soluble gp120 (sgp120) has been detected in PLWH plasma and its presence is linked to immune dysfunction. It was reported that sgp120 binding to CD4 on uninfected bystander CD4⁺ T cells sensitises them to cellular death via antibody-dependent cellular cytotoxicity (ADCC) mediated by non-neutralising anti-cluster A antibodies (Abs) present in PLWH plasma.

Methods: We included plasma from 520 PLWH on ART from three independent cohorts for measurements of anti-cluster A Abs and anti-CD4 binding site (anti-CD4BS) Abs. Associations between CD4⁺ T cell counts and anti-cluster A Abs was assessed using generalised least squares linear regression models, adjusting for potential confounders including age, sex, nadir CD4 and duration of ART. The role of anti-CD4BS Abs was evaluated using flow-cytometry based ADCC assays with primary CD4⁺ T cells.

Findings: We observed that non-neutralising anti-cluster A Abs are negatively associated with CD4⁺ T cell counts. Anti-CD4BS antibodies blocked the coating of uninfected bystander cells by sgp120, thereby preventing their elimination by ADCC. Supporting a protective role of anti-CD4BS antibodies, their presence in PLWH plasma abrogated the negative association between CD4 counts and anti-cluster A Abs.

Interpretation: Our results reveal that anti-cluster A Abs are associated with immune dysfunction in PLWH and anti-CD4BS antibodies might have a beneficial impact in these individuals.

Funding: This study was supported by the Canadian Institutes of Health Research, the Canada Foundation for Innovation, the Fonds de Recherche du Québec-Santé, and the National Institutes of Health.

Keywords: ADCC; Anti-cluster A antibodies; CD4 binding site antibodies; CD4(+) T cells depletion; HIV; Soluble gp120.

Fig. 1

Uninfected bystander CD4⁺ T cells are eliminated by ADCC responses mediated by plasma from PLWH. (A) Activated primary CD4⁺ T cells were infected with GFP reporter HIV_{NL4.3.ADA.GFP WT} virus. Three days post infection, autologous uninfected CD4⁺ T cells were stained with the eFluor450 dye and co-cultured with mock-infected or HIV-1-infected cells (eFluor450⁻GFP+ cells) for 2 days in the presence or absence of anti-CD4BS Fab fragments (20 μg/mL) (B–D). (C) Recognition and (D) ADCC-mediated elimination of uninfected bystander cells, designated eFluor450⁺GFP− cells, by plasma from 5 uninfected or 6 PLWH individuals were evaluated by flow cytometry. Shown in (B) are the gating strategy and representative staining obtained with PLWH plasma. The graphs shown represent (C) the median fluorescence intensity (MFI) and (D) the percentage of ADCC obtained with different plasmas. Error bars indicate means ± standard error of the mean (SEM). Statistical significance between no Fab and with Fab conditions was tested using a two-way ANOVA with a Holm–Sidak's post-test (∗∗∗∗p < 0.0001).

Fig. 2

Plasma from PLWH with anti-CD4BS Abs protect uninfected bystander CD4⁺ T cells from ADCC responses. (A) Activated primary CD4⁺ T cells stained with the eFluor450 dye and then coated with sgp120-Abs complexes. These coated cells were subsequently co-cultured with uncoated (eFluor450⁻CFSE+ cells) at a 1:1 ratio (B–D). (C) Recognition and (D) ADCC-mediated elimination of coated cells, designated eFluor450⁺CFSE− cells, by plasma from 13 uninfected or 37 PLWH individuals with or without anti-CD4BS Abs were evaluated by flow cytometry. Shown in (B) are the gating strategy and representative staining obtained with PLWH plasma. The graphs shown represent (C) the median fluorescence intensity (MFI) and (D) the percentage of ADCC obtained with different PLWH plasmas. Error bars indicate means ± standard error of the mean (SEM). Statistical significance between conditions was tested using an ordinary one-way ANOVA with a Holm–Sidak's post-test (ns, not significant, ∗∗∗p < 0.001, ∗∗∗∗p < 0.0001).

Fig. 3

Anti-cluster A Abs are negatively associated with CD4⁺T cell counts in PLWH and anti-CD4BS Abs abrogate this association. Correlations between CD4⁺ T-cell counts and anti–cluster A antibody levels are shown for the three cohorts tested (CHACS; upper row, PRESTIGIO; middle row and NIH; bottom row). Correlations are shown for (A) the total study population or stratified by (B) the absence or (C) presence of anti-CD4BS. Levels of anti–cluster A antibodies were log₂ transformed. The bold line represents a simple linear regression with the 95% confidence bands shown in the dotted line, and shaded in grey (total population), red (absence of anti-CD4BS Abs) or green (presence of anti-CD4BS Abs). Univariable and multivariable linear regressions were performed, with the beta coefficients representing the mean predicted change in absolute CD4⁺ T cell counts for each 1-log₂ increase in titres of anti–cluster A antibodies. Multivariable models are adjusted for age, sex, duration of antiretroviral therapy, and nadir CD4 counts.

Fig. 4

Restoration of CD4 counts is associated with a decline in anti-cluster A Abs levels. Matched longitudinal samples of 43 aviremic participants from the CHACS cohort were stratified based on the increase (left-panel) or the decrease (right-panel) in CD4 counts. (A) CD4 counts levels for both strata are shown and levels of anti-cluster A Abs were measured among these participants and are shown in (B). The bar represents the mean of each group, with a line connecting each matched participant. Statistical significance between visits was tested using a paired t test (ns, not significant, ∗∗∗∗p < 0.0001).