Anti-HIV Antibody Responses and the HIV Reservoir Size during Antiretroviral Therapy

Abstract

Background: A major challenge to HIV eradication strategies is the lack of an accurate measurement of the total burden of replication-competent HIV (the "reservoir"). We assessed the association of anti-HIV antibody responses and the estimated size of the reservoir during antiretroviral therapy (ART).

Methods: We evaluated anti-HIV antibody profiles using luciferase immunoprecipitation systems (LIPS) assay in relation to several blood-based HIV reservoir measures: total and 2-LTR DNA (rtPCR or droplet digital PCR); integrated DNA (Alu PCR); unspliced RNA (rtPCR), multiply-spliced RNA (TILDA), residual plasma HIV RNA (single copy PCR), and replication-competent virus (outgrowth assay). We also assessed total HIV DNA and RNA in gut-associated lymphoid tissue (rtPCR). Spearman correlations and linear regressions were performed using log-transformed blood- or tissue-based reservoir measurements as predictors and log-transformed antibody levels as outcome variables.

Results: Among 51 chronically HIV-infected ART-suppressed participants (median age = 57, nadir CD4+ count = 196 cells/mm3, ART duration = 9 years), the most statistically significant associations were between antibody responses to integrase and HIV RNA in gut-associated lymphoid tissue (1.17 fold-increase per two-fold RNA increase, P = 0.004) and between antibody responses to matrix and integrated HIV DNA in resting CD4+ T cells (0.35 fold-decrease per two-fold DNA increase, P = 0.003). However, these associations were not statistically significant after a stringent Bonferroni-adjustment of P<0.00045. Multivariate models including age and duration of ART did not markedly alter results.

Conclusions: Our findings suggest that anti-HIV antibody responses may reflect the size of the HIV reservoir during chronic treated HIV disease, possibly via antigen recognition in reservoir sites. Larger, prospective studies are needed to validate the utility of antibody levels as a measure of the total body burden of HIV during treatment.

Conflict of interest statement

Competing Interests: The authors have declared that no competing interests exist.

Figures

Fig 1. Antibody profiles against seven different HIV-1 antigens in the HIV cohort used for reservoir measurements.

The antibody levels against each of the seven HIV proteins were determined in HIV-uninfected (N = 8) and HIV-infected ART-suppressed (N = 51) participants. The antibody levels are plotted on the Y-axis using a log10scale, and the geometric mean with 95% CI are shown. Comparison between the two groups for all the antigens revealed highly statistically significant higher antibody responses in HIV-infected participants (p<0.0001), as expected. Abbreviations: GP120 = envelope glycoprotein 120; GP41 = envelope glycoprotein 41; RT = reverse transcriptase; INT = integrase; PR = protease; MA = matrix; CA = capsid; NV = HIV-uninfected; HIV = HIV-infected.

Fig 2. Lowess plot of log2-transformed HIV RNA in GALT (rtPCR) versus log2-transformed integrase antibody levels.

Abbreviations: LU = light units; GALT = gut-associated lymphoid tissue.

Fig 3. Lowess plot of log2-transformed integrated HIV DNA in peripheral resting CD4+ T cells (Alu-gag PCR) versus log2-transformed matrix antibody levels.

Abbreviations: LU = light units.

Fig 4. Spearman rank correlations of log2-transformed predictors (HIV reservoir measures in rows) versus log2-transformed outcomes (HIV antibody levels in columns).

Correlation coefficients shown in each box with p-values below. Abbreviations: GP120 = envelope glycoprotein 120; GP41 = envelope glycoprotein 41; RT = reverse transcriptase; INT = integrase; PR = protease; MA = matrix; CA = capsid; rtPCR = reverse transcriptase polymerase chain reaction (PCR); ddPCR = droplet digital PCR; Alu PCR = PCR using a primer in an Alu element to detect integrated HIV-1 DNA; LTR = long terminal repeat; Gag = HIV-1 Gag protein; rCD4 = resting CD4+ T cells; PBMC = peripheral blood mononuclear cells; SCA = single copy assay.