Induction of HIV-1-specific mucosal immune responses following intramuscular recombinant adenovirus serotype 26 HIV-1 vaccination of humans

Abstract

Background: Defining mucosal immune responses and inflammation to candidate human immunodeficiency virus type 1 (HIV-1) vaccines represents a current research priority for the HIV-1 vaccine field. In particular, it is unclear whether intramuscular immunization can elicit immune responses at mucosal surfaces in humans.

Methods: In this double-blind, randomized, placebo-controlled clinical trial, we evaluated systemic and mucosal immune responses to a candidate adenovirus serotype 26 (Ad26) vectored HIV-1 envelop (Env) vaccine in baseline Ad26-seronegative and Ad26-seropositive healthy volunteers. Systematic mucosal sampling with rectal Weck-Cel sponges and rectal biopsies were performed.

Results: Intramuscular immunization elicited both systemic and mucosal Env-specific humoral and cellular immune responses in the majority of subjects. Individuals with preexisting Ad26-specific neutralizing antibodies had vaccine-elicited immune responses comparable to those of subjects who were Ad26 seronegative. We also observed no increase in activated total or vector-specific mucosal CD4+ T lymphocytes following vaccination by either histopathology or flow cytometry.

Conclusions: These data demonstrate that a single intramuscular administration of this Ad26-vectored HIV-1 Env vaccine elicited both systemic and mucosal immune responses in humans. Induction of antigen-specific humoral and cellular mucosal immunity was not accompanied by a detectable increase in mucosal inflammation.

Clinical trials registration: NCT01103687.

Keywords: HIV; adenovirus; mucosal immunity; vaccine.

Figure 1.

Antibody responses. A, Individual adenovirus serotype 26 (Ad26) peripheral neutralizing antibody (NAb) responses from subjects by week and group are shown. Dots show individual responses at a given time point. Red horizontal lines show the mean values at a given time point for the group. The dashed horizontal line represents threshold for assay positivity. Solid circles = placebo Ad26⁻ subjects and open circles = placebo Ad26⁺ subjects at baseline. B and C, Individual envelop A (EnvA) enzyme-linked immunosorbent assay responses for the peripheral and mucosal compartments from subjects by week and group are shown for immunoglobulin G (IgG; B) and immunoglobulin A (IgA; C). Dots show individual responses at a given time point. Red horizontal lines show the mean values at a given time point for the group. The dashed horizontal line represents threshold for assay positivity. B, Peripheral group 1 vs group 2: P = .9 (week 2), P = .7 (week 8), and P = .7 (week 24); mucosal group 1 vs group 2: P = .6 (week 2), P = 1 (week 24).

Figure 2.

Antigen and vector intracellular cytokine staining (ICS) responses. A, Peripheral and mucosal adenovirus serotype 26 (Ad26) CD4⁺ ICS responses are shown as percentage of interferon (IFN) γ-positive cells. Dots represent individual responses at a given time point. The red horizontal lines show the mean values at a given time point for the group. The dashed horizontal line represents threshold for assay positivity. Group 1 vs group 2: P = not significant (weeks 2 and 24) for both peripheral and mucosal. Solid circles = placebo Ad26⁻ subjects and open circles = placebo Ad26⁺ subjects at baseline. B, Peripheral and mucosal envelop A (EnvA) CD8⁺ ICS responses are shown as percentage of IFN-γ–positive cells. Dots represent individual responses at a given time point. The red horizontal lines show the mean values at a given time point for the group. The dashed horizontal line represents threshold for assay positivity. Peripheral group 1 vs group 2: P = .2 (week 2) and P = .6 (week 24); mucosal group 1 vs group 2: P = .8 (week 2) and P = .6 (week 24). C, Peripheral and mucosal EnvA CD4⁺ ICS responses are shown as percentage of IFN-γ–positive cells. Dots represent individual responses at a given time point. The red horizontal lines show the mean values at a given time point for the group. The dashed horizontal line represents threshold for assay positivity. Peripheral group 1 vs group 2: P = .08 (week 2), P = 1 (week 24); mucosal group 1 vs group 2: P = .003 (week 2), P = .4 (week 24). Abbreviation: PBMC, peripheral blood mononuclear cell.

Figure 3.

Colorectal histopathology. Colorectal histopathology evaluation showing cellular subsets by group and week after vaccination: CD4 and CD8 (A), CD3 and CD25 (B), and Ki67 and human leukocyte antigen DR (HLA-DR) activation markers (C). Dots represent individual responses at a given time point as number of cells per 10 high-power fields (hpf). The red horizontal lines show the mean values at a given time point for the group. A–C, Group 1 vs group 2: P = not significant (week 2 and 24) for CD4 and CD8 (A), CD3 and CD25 (B), and Ki67 and HLA-DR (C). Abbreviation: Ad26, adenovirus serotype 26.

Figure 4.

Mucosal pathology. Representative images of immunohistochemistry from rectal mucosal biopsy specimens including CD3 (A), CD4 (B), CD8 (C), human leukocyte antigen DR (D), and Ki67 (E). All images shown at original magnification of ×200.

Figure 5.

Ki67 and CCR5⁺ CD4⁺ T-cell mucosal activation. A, Percentage of Ki67 expression by total and adenovirus serotype 26 (Ad26)-specific mucosal CD4⁺ T lymphocytes. B, Percentage of CCR5⁺ expression by total and Ad26-specific mucosal CD4⁺ T lymphocytes. A and B, Group 1 vs group 2: P = not significant (weeks 2 and 24) for total and Ad26-specific responses by Ki-67 and CCR5. In the placebo group, filled circles = placebo Ad26⁻ subjects and open circles = placebo Ad26⁺ subjects at baseline.