HIV infection Worsens Age-Associated Defects in Antibody Responses to Influenza Vaccine

Abstract

Background: Antibody responses to seasonal influenza vaccines are defective during older age and human immunodeficiency virus (HIV) infection. The effect of HIV on immune function in aging is relatively unknown.

Methods: HIV-infected and HIV-uninfected young women (age, 19-54 years) and older women (age, >55 years) were evaluated for B-cell and T-cell responses before and 4 weeks after influenza vaccination.

Results: Frequencies of seroprotection pre-vaccination and vaccine responsiveness (≥4-fold increase in antibody titer) were lower in HIV-infected participants than in age-matched HIV-uninfected participants. A subgroup of vaccine nonresponders were compared to responders and found to have reduced frequencies of memory B cells and antigen-specific antibody-secreting cells after vaccination. Frequencies of peripheral T-follicular helper (pTfh) cells correlated with memory B-cell function and influenza A(H1N1) antibody titers. Serologic and immunologic deficits were most frequent in older HIV-infected participants. Underlying CD4(+) T-cell immune activation and inflammation correlated negatively with antibody titers and B-cell function, which was not enhanced by exogenous interleukin 21 supplementation in HIV-infected, older vaccine nonresponders.

Conclusions: Immune activation associated with HIV infection and impaired pTfh function heighten deficiencies in antibody responses to influenza vaccine in older individuals. Strategies to reduce immune activation or augment pTfh function may enhance antibody responses in the aging HIV-infected population.

Keywords: CD4 T-cell immune activation; HIV infection; IL-21; aging; inflammation; memory B cells; peripheral T follicular helper cells; seasonal influenza vaccination.

Figure 1.

Age and human immunodeficiency virus (HIV) infection status contribute to impaired antibody (Ab) responses to influenza vaccination. Linear correlation between hemagglutination inhibition (HAI) Ab titers after vaccination and age in HIV-uninfected and HIV-infected young and older women (Table 1). P values were calculated from planned comparisons of general linear mixed model mean values. Correlation between HIV-infected subjects is indicated by the continuous line. The dashed line shows the correlation between the 2 variables when only the HIV-uninfected participants were taken into account.

Figure 2.

Impaired memory B-cell responses to influenza vaccination in aging and human immunodeficiency virus (HIV) infection. Cryopreserved peripheral blood mononuclear cells (PBMCs) from HIV-uninfected and HIV-infected responders (7 young uninfected participants, 5 young infected participants, 6 older uninfected participants, and 6 older infected participants) and nonresponders (5 young uninfected participants, 7 young infected participants, 6 older uninfected participants, and 6 older infected participants) before and after vaccination were thawed and rested overnight followed by staining with monoclonal antibody (Ab). Frequencies of resting memory (RM) B cells (CD20⁺CD21^hiCD27⁺CD10⁻; A) and interleukin 21 receptor–expressing (IL-21R⁺) RM B cells (B) before vaccination (Pre) and after vaccination (Post). C, H1N1-specific memory B-cell responses measured by an enzyme-linked immunosorbent spot assay in PBMCs stimulated with H1N1 antigen for 5 days. D, Linear correlation between H1N1-specific Ab-secreting cell (ASC) and RM B-cell frequencies after vaccination in HIV-uninfected and HIV-infected participants. Box plots include median with 25th and 75th percentile borders, and error bars represent 10th and 90th percentiles. *P < .05, **P < .01, and ***P < .001. Abbreviation: IgG, immunoglobulin G.

Figure 3.

Association of impaired antibody (Ab) response with defective peripheral T-follicular helper (pTfh)–cell frequency and function. A, Flow cytometric dot plots showing the gating strategy of pTfh cells (CD3⁺CD4⁺CD45RO⁺CXCR5⁺) from live (ViViD⁻) CD3⁺ cells. B, Frequencies of pTfh cells before and after vaccination in human immunodeficiency virus (HIV)-uninfected and HIV-infected young and older responders and nonresponders. B, Frequencies of interleukin 21–expressing (IL-21⁺) pTfh cells in responders and nonresponders following H1N1 antigen stimulation for 12 hours and intracellular staining. D, Frequencies of inducible T-cell costimulatory–expressing (ICOS⁺) pTfh cells in vaccine responders and nonresponders. E, Correlation between H1N1-specific Ab-secreting cell (ASC) responses with frequencies of pTfh cells after vaccination. Abbreviation: IgG, immunoglobulin G.

Figure 4.

Association between CXCR3⁻ peripheral T-follicular helper (pTfh) cells with antibody (Ab) responses to influenza vaccination in human immunodeficiency virus (HIV)-infected and HIV-uninfected participants. Cryopreserved peripheral blood mononuclear cells (PBMCs) from HIV-uninfected participants (7 young participants and 7 older participants) and HIV-infected participants (7 young participants and 7 older participants) before and after vaccination were stained with monoclonal Ab to determine frequencies of the programmed cell death 1–expressing (PD-1⁺) CXCR3⁻ pTfh-cell subset (gated from CD4⁺CD45RO⁺CXCR5⁺ cells) by flow cytometry (A). B, Frequencies of interleukin 21–expressing (IL-21⁺) PD-1⁺CXCR3⁻ pTfh cells at baseline and after vaccination in all groups following H1N1 antigen (5 µg/mL) stimulation. C, Association between frequencies of PD-1⁺CXCR3⁻ pTfh-cell subset and hemagglutination inhibition (HAI) titers after vaccination. D, PBMCs obtained from participants before and after vaccination were cultured for 5 days with H1N1 antigen with or without recombinant IL-21 (50 ng/mL). After 5 days, cells were analyzed by a B-cell enzyme-linked immunosorbent spot assay. Abbreviation: IgG, immunoglobulin G.

Figure 5.

Baseline CD4⁺ T-cell immune activation and the proinflammatory cytokine tumor necrosis factor α (TNF-α) is associated with impaired cellular responses to influenza vaccination. A, Prevaccination frequencies of activated CD4⁺ T cells (HLA-DR⁺CD38⁺) in human immunodeficiency virus (HIV)-uninfected and HIV-infected responders and nonresponders. Plasma levels of TNF-α (B) and interleukin 6 (IL-6; C) before vaccination in young and older responders and nonresponders were estimated using Milliplex beads (Magpix). Linear correlation between frequencies of CD4 immune activation with resting memory B cells (D), antibody-secreting cell (ASC) responses (E), and pTfh frequencies (F) after vaccination. Correlation of baseline plasma TNF-α levels with resting memory B cells (G), ASC responses (H), and pTfh-cell frequencies (I) after vaccination. *P < .05, **P < .01, ***P < .001, and ****P < .0001. Abbreviation: IgG, immunoglobulin G.