Identification of human genetic variants modulating the course of COVID-19 infection with importance in other viral infections

Introduction: COVID-19 has been a major focus of scientific research since early 2020. Due to its societal, economic, and clinical impact worldwide, research efforts aimed, among other questions, to address the effect of host genetics in susceptibility and severity of COVID-19.Methods: We, therefore, performed next-generation sequencing of coding and regulatory regions of 16 human genes, involved in maintenance of the immune system or encoding receptors for viral entry into the host cells, in a subset of 60 COVID-19 patients from the General Hospital Tešanj, Bosnia and Herzegovina, classified into three groups of clinical conditions of different severity (“mild,” “moderate,” and “severe”).Results: We confirmed that the male sex and older age are risk factors for severe clinical picture and identified 13 variants on seven genes (CD55, IL1B, IL4, IRF7, DDX58, TMPRSS2, and ACE2) with potential functional significance, either as genetic markers of modulated susceptibility to SARS-CoV-2 infection or modifiers of the infection severity. Our results include variants reported for the first time as potentially associated with COVID-19, but further research and larger patient cohorts are required to confirm their effect.Discussion: Such studies, focused on candidate genes and/or variants, have a potential to answer the questions regarding the effect of human genetic makeup on the expected infection outcome. In addition, loci we identified here were previously reported to have clinical significance in other diseases and viral infections, thus confirming a general, broader significance of COVID-19-related research results following the end of the pandemic period

Challenges in obtaining high-quality data from a custom-made panel for the next generation sequencing (NGS) using Ion Torrent GeneStudio™ S5 platform

The goal of this part of the study was to optimize the sequencing procedure for 16 human genes and their regulatory regions that might be associated with differential immunological response to COVID-19. The study was performed on 60 COVID-19 patients from the General Hospital of Tešanj, Bosnia and Herzegovina, categorized into three groups of mild, moderate, and severe clinical manifestation, based on the diagnosis by the residential physician. Target coding sequences and their regulatory regions were amplified for the following genes: HLA-A, HLA-B, HLA-C, ACE2, IL-6, IL-4, TMPRSS2, IFITM3, IL-12, RIG-I/DDX58, IRF-7, IRF-9, IL-1B, IL-1A, CD55, and TNF-α. DNA was isolated from the whole blood samples stored at -20°C for six months using QIAamp® DNA Mini Kit according to manufacturer’s instructions. Since NGS analysis of target genomic regions was performed on the Ion Torrent GeneStudio™ S5 platforms, libraries were prepared using Ion AmpliSeq™ Library Kit Plus according to manufacturer’s instructions in a protocol optimized for low-quality DNA. Due to dissatisfactory sequencing results, further protocol optimization steps were employed through separating two primer pools, increasing the number of PCR cycles, and decreasing the annealing temperature for the primer pool which showed poorer amplification results. In the end, 36 samples produced optimal results, while the remaining 24 samples will be re-sequenced following repeated sample collection and DNA isolation, accompanied by additional protocol modifications