Sex differences in innate anti-viral immune responses to respiratory viruses

Regis, E.; Fontanella, S.; Lin, L.; Howard, R.; Haider, S.; Curtin, J. A.; Edwards, M. R.; Rattray, M.; Simpson, A.; Custovic, A.; Johnston, S. L.

Males have excess morbidity and mortality from respiratory viral infections and especially so in COVID-19. The mechanisms explaining this excess in disease burden in males are unknown. Innate immune responses are likely critical in protection against a novel virus like SARS-CoV-2. We hypothesised that innate immune responses may be deficient in males relative to females. To test this we stimulated peripheral blood mononuclear cells (PBMCs) from participants in a population-based birth cohort with three respiratory viruses (rhinoviruses-RV-A16 and RV-A1, and respiratory syncytial virus-RSV) and two viral mimics (R848 and CpG-A, to mimic responses to SARS-CoV-2). We measured interferon (IFN) and IFN-induced chemokine responses and investigated sex differences in virus-induced responses. IFN-, IFN-{beta} and IFN-{gamma} responses to RV-A16 were deficient in males compared to females, fold-inductions being 1.92-fold (P<0.001), 2.04-fold (P<0.001) and 1.77-fold (P=0.003) lower in males than females, respectively. Similar significant deficiencies in innate immune responses were observed in males for eleven other cytokine-stimulus pairs. Responses in males were greater than those in females in only one of 35 cytokine-stimulus pairs investigated. Review of healthcare records revealed that 12.1% of males but only 6.6% of females were admitted to hospital with respiratory infections in the first year of life (P=0.017). Impaired innate anti-viral immunity in males likely results in high morbidity and mortality from respiratory viruses including COVID-19. Males may preferentially benefit from therapies that boost innate anti-viral immune responses.