Sex-biased expression of the TLR7 gene in severe COVID-19 patients: Insights from transcriptomics and epigenomics

Sex Chromosomes and Gonads Shape the Sex-Biased Transcriptomic Landscape in Tlr7-Mediated Demyelination During Aging

Demyelination occurs in aging and associated diseases, including Alzheimer's disease. Several of these diseases exhibit sex differences in prevalence and severity. Biological sex primarily stems from sex chromosomes and gonads releasing sex hormones. To dissect mechanisms underlying sex differences in demyelination of aging brains, we constructed a transcriptomic atlas of cell type-specific responses to illustrate how sex chromosomes, gonads, and their interaction shape responses to demyelination. We found that sex-biased oligodendrocyte and microglial responses are driven by interaction of sex chromosomes and gonads prior to myelin loss. Post demyelination, sex chromosomes mainly guide microglial responses, while gonadal composition influences oligodendrocyte signaling. Significantly, ablation of the X-linked gene Toll-like receptor 7 (Tlr7), which exhibited sex-biased expression during demyelination, abolished the sex-biased responses and protected against demyelination.

Long-term survival after intensive care for COVID-19: a nationwide cohort study of more than 8000 patients

BACKGROUND

Was it worth it-what is the outcome after the extended ICU (intensive care unit) length of stay for COVID-19 patients? Surprisingly, data on long-term mortality in large cohorts are lacking. We investigate long-term mortality including differences between men and women, as previous studies show that men generally suffer a more severe course of COVID-19 in terms of severity of illness and short-term mortality.

METHODS

Nationwide cohort including all adult COVID-19 patients admitted to Swedish ICUs until August 12, 2022. Primary outcome was 360-day mortality after ICU admission. Logistic regression was used to estimate associations between demographics, comorbidities, clinical characteristics and mortality.

RESULTS

In total, 8392 patients were included. Median (IQR) age was 63 (52-72) years and the majority (70.1%) were men. Among the 7390 patients with complete 360-day mortality data, 1775 (24.4%) patients died within 30 days, 2125 (28.8%) within 90 days and 2206 (29.8%) within 360 days from ICU admission. 360-day mortality was 27.1% in women and 31.0% in men. Multivariable logistic regression analysis showed increased risk of 360-day mortality in men compared to women (OR: 1.33, 95% CI: 1.17-1.52). Other variables associated with poor 360-day mortality were age, cardiac disease, COPD/asthma, diabetes, immune deficiency, chronic kidney disease, neuromuscular disease, and malignancy.

CONCLUSION

This study confirms the increased severity of disease in critically ill men with COVID-19, even in a long-term perspective. However, mortality beyond 90 days was strikingly low, indicating high probability of survival after the acute phase of illness.

Sex chromosome complement and sex steroid signaling underlie sex differences in immunity to respiratory virus infection

Epidemiological studies have revealed sex differences in the incidence and morbidity of respiratory virus infection in the human population, and often these observations are correlated with sex differences in the quality or magnitude of the immune response. Sex differences in immunity and morbidity also are observed in animal models of respiratory virus infection, suggesting differential dominance of specific immune mechanisms. Emerging research shows intrinsic sex differences in immune cell transcriptomes, epigenomes, and proteomes that may regulate human immunity when challenged by viral infection. Here, we highlight recent research into the role(s) of sex steroids and X chromosome complement in immune cells and describe how these findings provide insight into immunity during respiratory virus infection. We focus on the regulation of innate and adaptive immune cells by receptors for androgen and estrogens, as well as genes with a propensity to escape X chromosome inactivation. A deeper mechanistic knowledge of these pathways will help us to understand the often significant sex differences in immunity to endemic or pandemic respiratory pathogens such as influenza viruses, respiratory syncytial viruses and pathogenic coronaviruses.