Male testosterone levels may weaken vaccine response

U.S. researchers suggest male testosterone levels may partially explain why men often have weaker responses to vaccines than women. Mark M. Davis of the Stanford University School of Medicine and an investigator with the Howard Hughes Medical Institute and colleagues identified a link between certain genes affected by testosterone and antibody responses to an influenza vaccine. Previous research showed men typically experience more severe viral and other microbial infections than women, who tend to mount stronger immune responses to infections and vaccinations. In thi study, Davis and colleagues analyzed the antibody responses of 53 women and 34 men of various ages to the 2008-09 seasonal influenza vaccine. Compared to the men, the women produced antibodies that in laboratory tests could more effectively neutralize the influenza virus. The findings suggested testosterone levels may partially explain why men often have weaker responses to vaccines than women. To explain this difference, the scientists searched for patterns in gene expression, or the degree to which specific genes are turned on or off. Davis and the team found men with weak vaccine responses tended to have high expression levels of a certain cluster of genes involved in the metabolism of fats. The study, published in Proceedings of the National Academy of Sciences, found men with high levels of testosterone and elevated expression of the gene cluster had weaker antibody responses to the vaccine than women and men with low testosterone.