HIV controllers with HLA-DRB1*13 and HLA-DQB1*06 alleles have strong, polyfunctional mucosal CD4+ T-cell responses

Abstract

A small percentage of human immunodeficiency virus (HIV)-infected individuals, termed elite controllers, are able to spontaneously control HIV replication in blood. As the gastrointestinal mucosa is an important site of HIV transmission and replication as well as CD4+ T-cell depletion, it is important to understand the nature of the immune responses occurring in this compartment. Although the role of the HIV-specific CD8+ T-cell responses in mucosal tissues has been described, few studies have investigated the role of mucosal HIV-specific CD4+ T cells. In this study, we assessed HIV-specific CD4+ T-cell responses in the rectal mucosa of 28 "controllers" (viral load [VL] of <2,000 copies/ml), 14 "noncontrollers" (VL of >10,000 copies/ml), and 10 individuals on highly active antiretroviral therapy (HAART) (VL of <75 copies/ml). Controllers had higher-magnitude Gag-specific mucosal CD4+ T-cell responses than individuals on HAART (P<0.05), as measured by their ability to produce gamma interferon (IFN-γ), interleukin-2 (IL-2), tumor necrosis factor alpha (TNF-α), and macrophage inflammatory protein 1β (MIP-1β). The frequency of polyfunctional mucosal CD4+ T cells was also higher in controllers than in noncontrollers or individuals on HAART (P<0.05). Controllers with the strongest HIV-specific CD4+ T-cell responses possessed class II HLA alleles, HLA-DRB1*13 and/or HLA-DQB1*06, previously associated with a nonprogression phenotype. Strikingly, individuals with both HLA-DRB1*13 and HLA-DQB1*06 had highly polyfunctional mucosal CD4+ T cells compared to individuals with HLA-DQB1*06 alone or other class II alleles. The frequency of polyfunctional CD4+ T cells in rectal mucosa positively correlated with the magnitude of the mucosal CD8+ T-cell response (Spearman's r=0.43, P=0.005), suggesting that increased CD4+ T-cell "help" may be important in maintaining strong CD8+ T-cell responses in the gut of HIV controllers.

FIG. 1.

HIV Gag-specific CD4⁺ T-cell responses in rectal mucosa (A to C) and peripheral blood (D to F). Panels A and D show the total percentages of CD4⁺ T cells capable of producing IFN-γ, IL-2, MIP-1β, and/or TNF-α in response to HIV Gag stimulation in rectal mucosa (EC versus subjects on HAART, P = 0.045) (A) and peripheral blood (D). Panels B and C show significant differences in CD4⁺ T-cell cytokine/chemokine expression in rectal mucosa between groups: IFN-γ (EC versus NC, P = 0.031; EC versus subjects on HAART, P = 0.035; VC versus NC, P = 0.0005; VC versus subjects on HAART, P = 0.004) (B); MIP-1β (EC versus NC, P = 0.004; EC versus subjects on HAART, P = 0.016; VC versus NC, P = 0.012) (C). Panels E and F show significant differences in CD4⁺ T-cell cytokine expression in peripheral blood between groups: IL-2 (EC versus NC, P = 0.008; EC versus subjects on HAART, P = 0.018; VC versus NC, P = 0.003; VC versus subjects on HAART, P = 0.001) (E); TNF-α (VC versus NC, P = 0.019; VC versus subjects on HAART, P = 0.006) (F). Horizontal bars represent the median response for each group. *, P < 0.05; **, P < 0.01; ***, P < 0.001.

FIG. 2.

HIV Gag-specific CD4⁺ T-cell polyfunctional responses in rectal mucosa and peripheral blood across subject groups. CD4⁺ T-cell polyfunctional responses in the rectal mucosa (A) and peripheral blood (B) of controllers, noncontrollers, and HAART-suppressed individuals. Colors in the pie charts represent 4-function cells (black), 3-function cells (purple), 2-function cells (dark blue), and 1-function cells (light blue). Values in the pie charts are the median total CD4⁺ T-cell response within each subject group. The bar charts below show the responses in controllers, noncontrollers, and HAART-suppressed individuals, broken down into individual functional categories using interquartile ranges. Asterisks below the bar charts show significant differences (P < 0.05; Wilcoxon rank test) between controllers and noncontrollers (red) or subjects on HAART (green).

FIG. 3.

HLA class II alleles in the study cohort. Frequencies of controllers and noncontrollers in the current study who have HLA-DRB1*13 alone, HLA-DQB1*06 alone, the combined HLA-DRB1*13/HLA-DQB1*06 haplotype, and other class II HLA alleles not previously stated.

FIG. 4.

Total HIV Gag-specific CD4⁺ responses in the rectal mucosa of individuals with or without HLA-DRB1*13 and/or HLA-DQB1*06. Percentages of CD4⁺ T cells responding in any way (IFN-γ, IL-2, MIP-1β, and/or TNF-α) to HIV Gag stimulation in controllers with or without HLA-DRB1*13 and/or HLA-DQB1*06 and in noncontrollers lacking these alleles. (Too few noncontrollers possessed either of these alleles for a meaningful comparison.) Horizontal bars represent the median response in each group. *, P < 0.05.

FIG. 5.

Polyfunctional HIV Gag-specific CD4⁺ T-cell responses in the rectal mucosa of controllers with or without HLA-DRB1*13 and/or HLA-DQB1*06. Colors in the pie charts represent 4-function cells (black), 3-function cells (purple), 2-function cells (dark blue), and 1-function cells (light blue). Values in the pie charts are the median total CD4⁺ T-cell response within each group. The bar charts below show the responses in controllers with HLA-DQB1*06 alone, with the HLA-DRB1*13/HLA-DQB1*06 haplotype, or without either allele, broken down into individual functional categories using interquartile ranges. The blue asterisk below the bar chart shows a significant difference (P < 0.05) between those with the HLA-DRB1*13/HLA-DQB1*06 haplotype and those with HLA-DQB1*06 alone.

FIG. 6.

Polyfunctional mucosal CD4⁺ T-cell responses correlate with the magnitude and polyfunctionality of the CD8⁺ T-cell response. Relationships between the magnitude of the total CD4⁺ T-cell response and the magnitude of the total CD8⁺ T-cell response (A), the frequency of the polyfunctional CD4⁺ T cells and the magnitude of the total CD8⁺ T-cell response (B), and the frequency of the polyfunctional CD4⁺ T cells and the frequency of the polyfunctional CD8⁺ T cells (C) in rectal mucosa of controllers and noncontrollers. Polyfunctional CD4⁺ T cells are defined as exhibiting 3 or 4 functional responses; polyfunctional CD8⁺ T cells are those which express 3, 4, or 5 functions. Linear-regression lines and Spearman's r correlations were calculated using the combined controller and noncontroller data set.