An inherent T cell deficit in healthy males to C. neoformans infection may begin to explain the sex susceptibility in incidence of cryptococcosis.

BACKGROUND

Cryptococcus neoformans, the causative agent of cryptococcosis, causes ~ 181,000 deaths annually, with males having a higher incidence of disease than females (7M:3F). The reason for this sex bias remains unclear. We hypothesized that this disparity was due to biological differences between the male and female immune response.

METHODS

Peripheral blood mononuclear cells (PBMCs) from healthy donors were isolated and infected with C. neoformans ± exogenous testosterone or 17-β-estradiol. C. neoformans, B, T, and NK cell proliferation was quantified by flow cytometry. Cytokine analysis was conducted via protein array or ELISA. Serological testing was conducted to determine previous exposure to C. neoformans.

RESULTS

C. neoformans proliferated more in male PBMCs. T cell percentages in both sexes were lower in infected versus uninfected cells. Male PBMCs had lower CD3, CD4, and CD8 T cells percentages during infection compared to females. Cytokine profiles showed differences in uninfected male and female PBMCs, which subsided during infection. Only one donor was sero-negative for prior C. neoformans exposure. There was an effect of estrogen in one dataset.

CONCLUSIONS

These results suggest that males show an inherent deficit in T cell response during infection, which may contribute to the increased incidence of disease in males.