RESUMO
BackgroundCOVID-19 has affected millions of people worldwide. Clinical manifestations range from severe cases with a lethal outcome to mild or asymptomatic cases. Although there is the same proportion of infected genders, men are more susceptible to severe COVID-19, with a higher risk of death than women. This sex-bias may be explained by biological pathways. MethodsWe performed an epidemiological survey from July 2020 to July 2021 including 1744 unvaccinated adult Brazilian couples with at least one infected spouse despite living together during the COVID-19 infection without protective measures. The presence or absence of infection was confirmed by RT-PCR and/or serology results. The couples were divided between groups where both partners were infected (concordant couples) or only one spouse remained asymptomatic despite the close contact with the infected one (discordant couples). Statistical analysis of the collected data was performed aiming to verify a differential transmitter potential between genders in household contact. ResultsThe combination of our data collected from concordant and discordant couples showed that the man is the first (or the only) affected in the major occurrences when compared to women. Our findings support other published surveys and are in concordance with previous studies of our group. ConclusionsThese observations support the hypothesis according to which male individuals are more efficient virus transmitters than females, independently of the use of protective masks. In short, the present study confirmed the existence of gender differences not only for susceptibility to infection and resistance to COVID-19 but also in the transmission rate. HIGHLIGHTSO_LIThere are sex differences in COVID-19 susceptibility and transmission between couples with direct contact without protective measures; C_LIO_LIMen are more efficient virus transmitters than women; C_LIO_LISex-bias in COVID-19 transmission can be explained by differences in viral load in saliva, immune response and also behavioural protective differences between genders. C_LI
RESUMO
BackgroundDespite the high number of individuals infected by SARS-CoV-2 who develop COVID-19 symptoms worldwide, many exposed individuals remain asymptomatic and/or stay uninfected. This could be explained by a combination of environmental (exposure, previous infection), epigenetic, and genetic factors. Aiming to identify genetic variants involved in SARS-CoV-2 resistance, we analyzed 86 discordant Brazilian couples where one was infected and symptomatic while the partner remained asymptomatic and seronegative despite sharing the same bedroom during the infection. The discordant partners had comparable ages, and genetic ancestry proportions. MethodsWhole-exome sequencing followed by a state-of-the-art method to call genotypes and haplotypes across the highly polymorphic MHC and LRC. ResultsWe observed a minor impact in antigen-presentation genes and KIR genes associated with resistance. Interestingly, genes related to immune modulation, mainly involved in NK cell killing activation/inhibition harbor variants potentially contributing to infection resistance. We hypothesize that individuals prone to produce higher amounts of MICA (possibly soluble), LILRB1, LILRB2, and low amounts of MICB, would be more susceptible to infection. ConclusionAccording to this hypothesis, quantitative differences in these NK activity-related molecules could contribute to resistance to COVID-19 down regulating NK cell cytotoxic activity in infected individuals but not in resistant partners.
