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Immune-correlates analysis of an HIV-1 vaccine efficacy trial reveals an association of nonspecific interferon-γ secretion with increased HIV-1 infection risk: a cohort-based modeling study.

Huang Y, Duerr A, Frahm N, Zhang L, Moodie Z, De Rosa S, McElrath MJ, Gilbert PB - PLoS ONE (2014)

Bottom Line: This association remains after accounting for CD4(+) or CD8(+) T-cell activation.We observed a moderate correlation between ELISpot mock responses and CD4(+) T-cells secreting IFN-γ (ρ = 0.33, p = 0.007).In addition, the effect of the Step vaccine on infection risk appeared to vary with ELISpot mock response levels, especially among participants who had pre-existing anti-Ad5 antibodies (interaction p = 0.04).

View Article: PubMed Central - PubMed

Affiliation: Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America; Public Health Science Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America.

ABSTRACT

Background: Elevated risk of HIV-1 infection among recipients of an adenovirus serotype 5 (Ad5)-vectored HIV-1 vaccine was previously reported in the Step HIV-1 vaccine efficacy trial. We assessed pre-infection cellular immune responses measured at 4 weeks after the second vaccination to determine their roles in HIV-1 infection susceptibility among Step study male participants.

Methods: We examined ex vivo interferon-γ (IFN-γ) secretion from peripheral blood mononuclear cells (PBMC) using an ELISpot assay in 112 HIV-infected and 962 uninfected participants. In addition, we performed flow cytometric assays to examine T-cell activation, and ex vivo IFN-γ and interleukin-2 secretion from CD4(+) and CD8(+) T cells. We accounted for the sub-sampling design in Cox proportional hazards models to estimate hazard ratios (HRs) of HIV-1 infection per 1-log(e) increase of the immune responses.

Findings: We found that HIV-specific immune responses were not associated with risk of HIV-1 infection. However, each 1-log(e) increase of mock responses measured by the ELISpot assay (i.e., IFN-γ secretion in the absence of antigen-specific stimulation) was associated with a 62% increase of HIV-1 infection risk among vaccine recipients (HR = 1.62, 95% CI: (1.28, 2.04), p<0.001). This association remains after accounting for CD4(+) or CD8(+) T-cell activation. We observed a moderate correlation between ELISpot mock responses and CD4(+) T-cells secreting IFN-γ (ρ = 0.33, p = 0.007). In addition, the effect of the Step vaccine on infection risk appeared to vary with ELISpot mock response levels, especially among participants who had pre-existing anti-Ad5 antibodies (interaction p = 0.04).

Conclusions: The proportion of cells, likely CD4(+) T-cells, producing IFN-γ without stimulation by exogenous antigen appears to carry information beyond T-cell activation and baseline characteristics that predict risk of HIV-1 infection. These results motivate additional investigation to understand the potential link between IFN-γ secretion and underlying causes of elevated HIV-1 infection risk among vaccine recipients in the Step study.

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Distribution of Immune Reponses in Infected and Uninfected Vaccine and Placebo Recipients in the Immune Correlates Analysis Study.Panel A includes the IFN-γ-secreting cellular responses measured by the ELISpot assay. Panel B includes T-cell activation responses measured by the flow cytometric assay. Box-plots show the 25th percentile (lower edge of the box), 50th percentile (horizontal line in the box), and 75th percentile (upper edge of the box) for the immune responses, with participants stratified according to HIV-1 infection status and treatment assignment. The tip of the vertical bars indicate the most extreme data points, which are no more than 1.5 times the interquartile range from the box. The distribution plots of other immune responses measured by the ICS assay are shown in Figures S2 of Information S1.
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pone-0108631-g002: Distribution of Immune Reponses in Infected and Uninfected Vaccine and Placebo Recipients in the Immune Correlates Analysis Study.Panel A includes the IFN-γ-secreting cellular responses measured by the ELISpot assay. Panel B includes T-cell activation responses measured by the flow cytometric assay. Box-plots show the 25th percentile (lower edge of the box), 50th percentile (horizontal line in the box), and 75th percentile (upper edge of the box) for the immune responses, with participants stratified according to HIV-1 infection status and treatment assignment. The tip of the vertical bars indicate the most extreme data points, which are no more than 1.5 times the interquartile range from the box. The distribution plots of other immune responses measured by the ICS assay are shown in Figures S2 of Information S1.

Mentions: We assessed cellular immune responses by ELISpot in 112 (n = 84 vaccine; n = 28 placebo) HIV-1 infected cases and 962 (n = 729 vaccine; n = 233 placebo) uninfected non-cases, T-cell activation in 116 (n = 71 vaccine; n = 45 placebo) cases and 586 (n = 257 vaccine; n = 229 placebo) non-cases, as well as T-cell responses by ICS in 51 (n = 31 vaccine; n = 24 placebo) cases and 42 vaccine non-cases (Figure 1). The vaccine was immunogenic as reported previously [9]. In addition, we observed a good dynamic range in all study subjects regardless of infection status for ELISpot mock and HIV-specific responses, as well as for T-cell activation (Figure 2) and ICS responses (Figure S2 in Information S1). These immune responses in cases tended to be comparable with or higher than those in non-cases; formal comparisons are presented later in this section to account for the sampling design and potential confounding factors. Descriptively, for ELISpot, among the vaccine recipients the median (interquartile range [IQR]) responses for Gag were 172 [87, 362] (cases: 181 [118, 331]; non-cases: 170 [83, 366]) SFC/million PBMC, for Pol 164 [85, 408] (cases: 178 [96, 375]; non-cases: 162 [84, 410]) SFC/million PBMC, for Nef 152 [73, 308] (cases: 173 [84, 283]; non-cases: 150 [72, 308]) SFC/million PBMC, and for mock 16 [9, 29] (cases: 24 [14, 46]; non-cases: 15 [8, 27]) SFC/million PBMC; among the placebo recipients, the median (IQR) mock response was 22 [14, 34] (cases: 26 [13, 37]; non-cases: 21 [14, 33]) SFC/million PBMC. For T-cell activation, among the vaccine recipients the median [IQR] was 0.81% [0.65%, 1.12%] Ki-67hiBcL-2l°CD4+ (cases: 0.86% [0.64%, 1.10%]; non-cases: 0.80% [0.66%, 1.12%]), and 0.59% [0.39%, 1.03%] Ki-67hiBcL-2l°CD8+ T cells (cases: 0.69% [0.43%, 1.19%]; non-cases: 0.57% [0.38%, 0.95%]); among the placebo recipients the median [IQR] was 0.82% [0.60%, 1.11%] Ki-67hiBcL-2l°CD4+ (cases: 0.88% [0.65%, 1.20%]; non-cases: 0.82% [0.59%, 1.09%]), and 0.53% [0.36%, 0.94%] Ki-67hiBcL-2l°CD8+ T cells (cases: 0.75% [0.35%, 1.23%]; non-cases: 0.53% [0.36%, 0.92%]). For ICS, among the vaccine recipients the median [IQR] CMV-specific responses were 0.13% [0.03%, 0.62%] IL-2+ and/or IFN-γ+ CD4+ (cases: 0.13% [0.04%, 0.28%]; non-cases: 0.13% [0.03%, 2.20%]), and 0.76% [0.06%, 2.56%] IL-2+ and/or IFN-γ+ CD8+ T cells (cases: 0.84% [0.28%, 1.87%]; non-cases: 0.60% [0.05%, 3.59%]); among the placebo recipients the median (IQR) CMV-specific responses (only available in cases) were 0.11% [0.01%, 0.22%] IL-2+ and/or IFN-γ+ CD4+ and 0.22% [0.01%, 1.05%] IL-2+ and/or IFN-γ+ CD8+ T cells (Figure S2 in Information S1). Because CD4+ and CD8+ T-cell responses detected by ICS were previously reported not to be associated with risk of HIV-1 infection [3] and there were a small number of infected and uninfected participants with available data, we refrained from further quantitative analysis of ICS responses.


Immune-correlates analysis of an HIV-1 vaccine efficacy trial reveals an association of nonspecific interferon-γ secretion with increased HIV-1 infection risk: a cohort-based modeling study.

Huang Y, Duerr A, Frahm N, Zhang L, Moodie Z, De Rosa S, McElrath MJ, Gilbert PB - PLoS ONE (2014)

Distribution of Immune Reponses in Infected and Uninfected Vaccine and Placebo Recipients in the Immune Correlates Analysis Study.Panel A includes the IFN-γ-secreting cellular responses measured by the ELISpot assay. Panel B includes T-cell activation responses measured by the flow cytometric assay. Box-plots show the 25th percentile (lower edge of the box), 50th percentile (horizontal line in the box), and 75th percentile (upper edge of the box) for the immune responses, with participants stratified according to HIV-1 infection status and treatment assignment. The tip of the vertical bars indicate the most extreme data points, which are no more than 1.5 times the interquartile range from the box. The distribution plots of other immune responses measured by the ICS assay are shown in Figures S2 of Information S1.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4219669&req=5

pone-0108631-g002: Distribution of Immune Reponses in Infected and Uninfected Vaccine and Placebo Recipients in the Immune Correlates Analysis Study.Panel A includes the IFN-γ-secreting cellular responses measured by the ELISpot assay. Panel B includes T-cell activation responses measured by the flow cytometric assay. Box-plots show the 25th percentile (lower edge of the box), 50th percentile (horizontal line in the box), and 75th percentile (upper edge of the box) for the immune responses, with participants stratified according to HIV-1 infection status and treatment assignment. The tip of the vertical bars indicate the most extreme data points, which are no more than 1.5 times the interquartile range from the box. The distribution plots of other immune responses measured by the ICS assay are shown in Figures S2 of Information S1.
Mentions: We assessed cellular immune responses by ELISpot in 112 (n = 84 vaccine; n = 28 placebo) HIV-1 infected cases and 962 (n = 729 vaccine; n = 233 placebo) uninfected non-cases, T-cell activation in 116 (n = 71 vaccine; n = 45 placebo) cases and 586 (n = 257 vaccine; n = 229 placebo) non-cases, as well as T-cell responses by ICS in 51 (n = 31 vaccine; n = 24 placebo) cases and 42 vaccine non-cases (Figure 1). The vaccine was immunogenic as reported previously [9]. In addition, we observed a good dynamic range in all study subjects regardless of infection status for ELISpot mock and HIV-specific responses, as well as for T-cell activation (Figure 2) and ICS responses (Figure S2 in Information S1). These immune responses in cases tended to be comparable with or higher than those in non-cases; formal comparisons are presented later in this section to account for the sampling design and potential confounding factors. Descriptively, for ELISpot, among the vaccine recipients the median (interquartile range [IQR]) responses for Gag were 172 [87, 362] (cases: 181 [118, 331]; non-cases: 170 [83, 366]) SFC/million PBMC, for Pol 164 [85, 408] (cases: 178 [96, 375]; non-cases: 162 [84, 410]) SFC/million PBMC, for Nef 152 [73, 308] (cases: 173 [84, 283]; non-cases: 150 [72, 308]) SFC/million PBMC, and for mock 16 [9, 29] (cases: 24 [14, 46]; non-cases: 15 [8, 27]) SFC/million PBMC; among the placebo recipients, the median (IQR) mock response was 22 [14, 34] (cases: 26 [13, 37]; non-cases: 21 [14, 33]) SFC/million PBMC. For T-cell activation, among the vaccine recipients the median [IQR] was 0.81% [0.65%, 1.12%] Ki-67hiBcL-2l°CD4+ (cases: 0.86% [0.64%, 1.10%]; non-cases: 0.80% [0.66%, 1.12%]), and 0.59% [0.39%, 1.03%] Ki-67hiBcL-2l°CD8+ T cells (cases: 0.69% [0.43%, 1.19%]; non-cases: 0.57% [0.38%, 0.95%]); among the placebo recipients the median [IQR] was 0.82% [0.60%, 1.11%] Ki-67hiBcL-2l°CD4+ (cases: 0.88% [0.65%, 1.20%]; non-cases: 0.82% [0.59%, 1.09%]), and 0.53% [0.36%, 0.94%] Ki-67hiBcL-2l°CD8+ T cells (cases: 0.75% [0.35%, 1.23%]; non-cases: 0.53% [0.36%, 0.92%]). For ICS, among the vaccine recipients the median [IQR] CMV-specific responses were 0.13% [0.03%, 0.62%] IL-2+ and/or IFN-γ+ CD4+ (cases: 0.13% [0.04%, 0.28%]; non-cases: 0.13% [0.03%, 2.20%]), and 0.76% [0.06%, 2.56%] IL-2+ and/or IFN-γ+ CD8+ T cells (cases: 0.84% [0.28%, 1.87%]; non-cases: 0.60% [0.05%, 3.59%]); among the placebo recipients the median (IQR) CMV-specific responses (only available in cases) were 0.11% [0.01%, 0.22%] IL-2+ and/or IFN-γ+ CD4+ and 0.22% [0.01%, 1.05%] IL-2+ and/or IFN-γ+ CD8+ T cells (Figure S2 in Information S1). Because CD4+ and CD8+ T-cell responses detected by ICS were previously reported not to be associated with risk of HIV-1 infection [3] and there were a small number of infected and uninfected participants with available data, we refrained from further quantitative analysis of ICS responses.

Bottom Line: This association remains after accounting for CD4(+) or CD8(+) T-cell activation.We observed a moderate correlation between ELISpot mock responses and CD4(+) T-cells secreting IFN-γ (ρ = 0.33, p = 0.007).In addition, the effect of the Step vaccine on infection risk appeared to vary with ELISpot mock response levels, especially among participants who had pre-existing anti-Ad5 antibodies (interaction p = 0.04).

View Article: PubMed Central - PubMed

Affiliation: Vaccine and Infectious Disease Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America; Public Health Science Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, United States of America.

ABSTRACT

Background: Elevated risk of HIV-1 infection among recipients of an adenovirus serotype 5 (Ad5)-vectored HIV-1 vaccine was previously reported in the Step HIV-1 vaccine efficacy trial. We assessed pre-infection cellular immune responses measured at 4 weeks after the second vaccination to determine their roles in HIV-1 infection susceptibility among Step study male participants.

Methods: We examined ex vivo interferon-γ (IFN-γ) secretion from peripheral blood mononuclear cells (PBMC) using an ELISpot assay in 112 HIV-infected and 962 uninfected participants. In addition, we performed flow cytometric assays to examine T-cell activation, and ex vivo IFN-γ and interleukin-2 secretion from CD4(+) and CD8(+) T cells. We accounted for the sub-sampling design in Cox proportional hazards models to estimate hazard ratios (HRs) of HIV-1 infection per 1-log(e) increase of the immune responses.

Findings: We found that HIV-specific immune responses were not associated with risk of HIV-1 infection. However, each 1-log(e) increase of mock responses measured by the ELISpot assay (i.e., IFN-γ secretion in the absence of antigen-specific stimulation) was associated with a 62% increase of HIV-1 infection risk among vaccine recipients (HR = 1.62, 95% CI: (1.28, 2.04), p<0.001). This association remains after accounting for CD4(+) or CD8(+) T-cell activation. We observed a moderate correlation between ELISpot mock responses and CD4(+) T-cells secreting IFN-γ (ρ = 0.33, p = 0.007). In addition, the effect of the Step vaccine on infection risk appeared to vary with ELISpot mock response levels, especially among participants who had pre-existing anti-Ad5 antibodies (interaction p = 0.04).

Conclusions: The proportion of cells, likely CD4(+) T-cells, producing IFN-γ without stimulation by exogenous antigen appears to carry information beyond T-cell activation and baseline characteristics that predict risk of HIV-1 infection. These results motivate additional investigation to understand the potential link between IFN-γ secretion and underlying causes of elevated HIV-1 infection risk among vaccine recipients in the Step study.

Show MeSH
Related in: MedlinePlus