Sex differences in cytokine profiles during suppressive antiretroviral therapy

Abstract

Objective: Despite lower plasma HIV RNA levels, women progress faster to AIDS than men. The reasons for these differences are not clear but might be a consequence of an elevated inflammatory response in women.

Methods: We investigated sex differences in cytokine profiles by measuring the concentrations of 36 cytokines/chemokines by Luminex in blood of women and men (sex at birth) with chronic HIV infection under suppressive therapy. We initially performed a principal component analysis to see if participants clustered by sex, and then fit a partial least squares discriminant analysis (PLS-DA) model where we used cytokines to predict sex at birth. The significance of the difference in nine cytokines with VIP greater than 1 was tested using Wilcoxon test-rank. Further, potential confounding factors were tested by multivariate linear regression models.

Results: Overall, we predicted sex at birth in the PLS-DA model with an error rate of approximately 13%. We identified five cytokines, which were significantly higher in women compared with men, namely the pro-inflammatory chemokines CXCL1 (Gro-α), CCL5 (RANTES), CCL3 (MIP-1α), CCL4 (MIP-1β), as well as the T-cell homeostatic factor IL-7. The effect of sex remained significant after adjusting for CD4 + , age, ethnicity, and race for all cytokines, except for CCL3 and race.

Conclusion: The observed sex-based differences in cytokines might contribute to higher immune activation in women compared with men despite suppressive therapy. Increased levels of IL-7 in women suggest that homeostatic proliferation may have a differential contribution to HIV reservoir maintenance in female and male individuals. Our study emphasizes the importance of sex-specific studies of viral pathogenesis.

Figure 1:. Projection of multivariate dimensionality reduction

(A) Principal component analysis of cytokine profiles in women compared to men with HIV on suppressive ART. PCA analysis on cytokine profile shows distinct clustering of men (orange triangles) and women (Blue circles). The first and second principal components explain 27% and 19% of the variance respectively. (B) Two-dimensional PLS-DA projections of cytokines in blood plasma of men and women with HIV on suppressive ART. Shown are PLS-DA projections spanned by the first two components of the PLS-DA model with ellipses representing Hotelling’s 2-samples T2 with 95% confidence intervals in blood plasma of men (orange triangles) and women (Blue circles). The E-statistic was used to test the statistical differences in the separation between the cytokine profiles in the 2 sex-based groups. The multivariate distance between men and women observations was significant in (p = <0.001).

Figure 2:. Effect of sex on chemokine/cytokine in blood plasma

Shown is the difference of the concentrations for 5 chemokine/cytokines (log10 normalized) in women and men infected with HIV on suppressive ART. The statistical significance of 9 cytokines with VIP>1 identified in the PLS-DA model were further tested for by Wilcoxon Rank Sum test. Five out of 9 remained significant. The concentrations of these 5 Chemokine/cytokine were log10-transformed and plotted as boxplots. For each cytokine and each boxplot, each point represents a participant’s cytokine concentration, the box represents the interquartile range (IQR), the middle line represents the median, while the points beyond the whiskers are outliers. All chemokine/cytokines had higher concentrations in women compared to men.