Role of genetic variants and host polymorphisms on COVID-19: From viral entrance mechanisms to immunological reactions.

Coronavirus disease 2019 (COVID-19), caused by a highly pathogenic emerging virus, is called severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Knowledge regarding the pathogenesis of this virus is in infancy; however, investigation on the pathogenic mechanisms of the SARS-CoV-2 is underway. In COVID-19, one of the most remarkable characteristics is the wide range of disease manifestation and severity seen across individuals of different ethnic backgrounds and geographical locations. To effectively manage COVID-19 in the populations, beyond SARS-CoV-2 detection, serological response assessment, and analytic techniques, it is critical to obtain knowledge about at-risk individuals and comprehend the identified variations in the disease's severity in general and also in the populations' levels. Several factors can contribute to variation in disease presentation, including population density, gender and age differences, and comorbid circumstances including diabetes mellitus, hypertension, and obesity. Genetic factors presumably influence SARS-CoV-2 infection susceptibility. Besides this, COVID-19 has also been linked with a higher risk of mortality in men and certain ethnic groups, revealing that host genetic characteristics may affect the individual risk of death. Also, genetic variants involved in pathologic processes, including virus entrance into cells, antiviral immunity, and inflammatory response, are not entirely understood. Regarding SARS-CoV-2 infection characteristics, the present review suggests that various genetic polymorphisms influence virus pathogenicity and host immunity, which might have significant implications for understanding and interpreting the matter of genetics in SARS-CoV-2 pathogenicity and customized integrative medical care based on population investigation.

Immunomodulatory roles of microbiota-derived short-chain fatty acids in bacterial infections.

In recent years, an overwhelming amount of evidence has positively recommended a significant role of microbiota in human health and disease. Microbiota also plays a crucial role in the initiation, preparation, and function of the host immune response. Recently, it has been shown that short-chain fatty acids (SCFAs) are the primary metabolites of the intestinal microbiota produced by anaerobic fermentation, which contributes to the host-pathogen interaction. SCFAs, such as propionate, acetate, and butyrate, are bacterial metabolites with immunomodulatory activity, and they are indispensable for the maintenance of homeostasis. Some evidence indicates that they are involved in the development of infections. In the present study, we provide the latest findings on the role of SCFAs in response to bacterial infections.