Sex affects immune response capacity against COVID-19 infection.

The genetic variability of each individual may lead to the identification of completely different genetic polymorphisms which are associated with a different sensitivity to infectious diseases in humans. Such genetic variability allows the immune system to respond differently to viral agents, therefore only a fraction of humans develop severe symptoms, as happened with SARS-CoV-2. Such knowledge is critical to enable the development of appropriate pharmacological solutions to prevent the consequences of insufficient immunity in dealing with serious viral diseases such as SARS-CoV-2. For instance, global epidemiological data show that male sex is a risk factor for the severe evolution of SARS-CoV-2 disease. Men, due to higher production of Testosterone (TLT), are more vulnerable than females. Women, due to greater expression of the TLR7 gene found on the X chromosome, a key innate immunity gene that encodes Toll-like proteins, are able to synthesise more antiviral proteins and interferons in dendritic cells, resulting in a more robust immune system capable of preventing severe SARS-CoV-2 viral disease. This manuscript highlights how human genetic variability can lead to severe infectious symptoms in some individuals who must take appropriate prophylactic actions, such as vaccination, to prevent this.