Systems analysis of sex differences reveals an immunosuppressive role for testosterone in the response to influenza vaccination

Abstract

Females have generally more robust immune responses than males for reasons that are not well-understood. Here we used a systems analysis to investigate these differences by analyzing the neutralizing antibody response to a trivalent inactivated seasonal influenza vaccine (TIV) and a large number of immune system components, including serum cytokines and chemokines, blood cell subset frequencies, genome-wide gene expression, and cellular responses to diverse in vitro stimuli, in 53 females and 34 males of different ages. We found elevated antibody responses to TIV and expression of inflammatory cytokines in the serum of females compared with males regardless of age. This inflammatory profile correlated with the levels of phosphorylated STAT3 proteins in monocytes but not with the serological response to the vaccine. In contrast, using a machine learning approach, we identified a cluster of genes involved in lipid biosynthesis and previously shown to be up-regulated by testosterone that correlated with poor virus-neutralizing activity in men. Moreover, men with elevated serum testosterone levels and associated gene signatures exhibited the lowest antibody responses to TIV. These results demonstrate a strong association between androgens and genes involved in lipid metabolism, suggesting that these could be important drivers of the differences in immune responses between males and females.

Keywords: aging; gender; immuno-endocrine; immunosenescence; sexual dimorphism.

Fig. 1.

Significant differences in baseline immune parameters between females and males. Expression of a total of 278 immune features and gene modules was compared between females (F) (n = 53) and males (M) (n = 34) of different age groups, including serum cytokines, chemokines, and growth factors; frequencies of over 15 blood cell subsets; phosphorylation events in multiple immune cells; and whole-genome gene expression using SAM. A cutoff of Q < 0.1 and absolute score(d) > 2 was considered significant (volcano plot; Top, Left). Inflammatory markers including LEPTIN, IL-1RA, and CRP and other serum proteins were elevated in females compared with males. mono.Unstimulated.STAT3, baseline levels of pSTAT3 in isolated monocytes. A single gene module (module 106) (Bottom, Right) was differentially expressed (and up-regulated in males). Module 106 is enriched for genes located on the Y chromosome (P < 10⁻⁹). Lower whisker represents the minimum value, lower hinge the first quartile, upper hinge the third quartile, and upper whisker the maximum value. Outliers are represented by circles.

Fig. 2.

Differences in baseline immune parameters between females and males by age group. The individuals were first divided by age group (58 older and 29 young), and the significant differences identified between all females (yellow bars) and males (blue bars) using SAM (seven in total; Fig. 1) were used to investigate differences in expression by age group. With the exception of mono.Unstimulated.STAT3, all significant differences between all males and females identified previously were also observed in both age groups (P < 0.05). However, the differences in LEPTIN, IL-1RA, and CRP were less pronounced in older individuals due to an overall increase in the levels of these proteins in the serum of older males compared with young males (P < 0.05). F, females; M, males. mono.Unstimulated.STAT3, baseline levels of pSTAT3 in isolated monocytes; mod_106, module enriched for Y chromosome genes.

Fig. 3.

Odds ratio for vaccine responses in males and females based on expression of module 052. Interaction analysis was conducted for sex and gene expression modules on the serological (microneutralization) responses to TIV (seroconversion to the H3N2 strain). A significant interaction was found between the variables sex and gene module 052. (A) Odds ratio for vaccine response given module 052 in females (red line) and males (blue line). (B) No significant interaction between sex and module 052 is observed for males with low levels of testosterone [Tlo (n = 17), brown line], although a significantly negative effect of module 052 is observed for males with high levels of testosterone [Thi (n = 17), blue line] (adjusted for confounders including age).