Due to their pivotal role in orchestrating the immune response, HLA loci were recognized as candidates for genetic association studies related to the severity of COVID‐19. Since the findings on the effects of HLA alleles on the outcome of SARS‐CoV‐2 infection remain inconclusive, we aimed to elucidate the potential involvement of genetic variability within HLA loci in the molecular genetics of COVID‐19 by classifying the articles according to different disease severity/outcomes and by conducting a systematic review with meta‐analysis. Potentially eligible studies were identified by searching PubMed, Scopus and Web of Science literature databases. A total of 28 studies with 13,073 participants were included in qualitative synthesis, while the results of 19 studies with 10,551 SARS‐CoV‐2‐positive participants were pooled in the meta‐analysis. According to the results of quantitative data synthesis, association with COVID‐19 severity or with the lethal outcome was determined for the following alleles and allele families: HLA‐A*01, HLA‐A*03, HLA‐A*11, HLA‐A*23, HLA‐A*31, HLA‐A*68, HLA‐A*68:02, HLA‐B*07:02, HLA‐B*14, HLA‐B*15, HLA‐B*40:02, HLA‐B*51:01, HLA‐B*53, HLA‐B*54, HLA‐B*54:01, HLA‐C*04, HLA‐C*04:01, HLA‐C*06, HLA‐C*07:02, HLA‐DRB1*11, HLA‐DRB1*15, HLA‐DQB1*03 and HLA‐DQB1*06 (assuming either allelic or dominant genetic model). We conclude that alleles of HLA‐A, ‐B, ‐C, ‐DRB1 and ‐DQB1 loci may represent potential biomarkers of COVID‐19 severity and/or mortality, which needs to be confirmed in a larger set of studies.

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Genes involved in the regulation of viral recognition and its entry into a host cell have been identified as candidates for genetic association studies on COVID-19 severity. Published findings on the effects of polymorphisms within ACE1 , ACE2 , TMPRSS2 , IFITM3 and VDR genes remained inconclusive, so we conducted a systematic review and meta-analysis in order to elucidate their potential involvement in the genetic basis underlying the severity of COVID-19 and/or an outcome of SARS-CoV-2 infection. Identification of potentially eligible studies was based on PubMed, Scopus and Web of Science database search. Relevant studies (n=29) with a total number of 8247 SARS-CoV-2-positive participants were included in qualitative synthesis, while results of 21 studies involving 5939 were pooled in meta-analysis. Minor allele I of rs1799752 located within ACE1 was identified as a protective variant against severe COVID-19, while its effect on mortality rate was opposite. Similarly, minor allele A of ACE2 polymorphism, rs2285666, was found to associate with a decreased risk of severe COVID-19 ( P = 0.003, OR = 0.512, 95 % CI = 0.331-0.793). Statistical significance was also seen for the association between COVID-19 severity and rs12329760 located within TMPRSS2 . Our results did not support the supposed association of rs12252 in IFITM3 and polymorphisms within VDR with disease severity. We conclude that genetic variants within ACE1 , ACE2 and TMPRSS2 may be potential biomarkers of COVID-19 severity, which needs to be further confirmed in a larger set of studies.

Glycosylation is co- and posttranslational modifications affecting proteins. The glycopattern changes are associated with changes in biological function and are involved in many diseases including cancer. We present the lectin-based protein microarray method enabling determination of differences in protein glycosylation. The method involves isolation of targeted protein from samples by immunoprecipitation, spotting of protein from multiple samples into arrays on a microarray slide, incubation with set of biotinylated lectins, the reaction with fluorescent conjugate of streptavidin, and detection of fluorescent intensities by microarray scanner. Lectin-based protein microarray was applied in investigation of differences in alpha-2-macroglobulin (α2M) glycosylation isolated from sera samples of healthy persons and patients with colorectal cancer (CC). From 14 lectins used in analysis, statistically significant differences (Student's t-test, P < 0.05) between two groups of samples (persons without cancer and CC patients) were found for 5 of them. α2M molecules isolated from sera of CC patients have higher content of α2,6 sialic acid, N-acetylglucosamine and mannose residues, and tri-/tetraantennary complex type high-mannose N-glycans. A novel lectin-based protein microarray developed and described can serve as a suitable analytical technique for sensitive, simple, fast, and high-throughput determination of differences in protein glycosylation isolated from serum or other samples.

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Insulin-like growth factors (IGFs) play active role in mitogenic and metabolic processes. In the peripheral circulation, they are mostly bound to specific IGF-binding proteins (IGFBPs). Proteolysis of IGFBPs releases free, active IGFs. IGFBP-2 is the second most abundant of the six binding proteins and its concentration increases in catabolic states. The possible interaction between IGFBP-2 and other proteins in the circulation was investigated in this study. Our results showed that IGFBP-2 associates with α2-macroglobulin (α2M), a protease inhibitor. Formation of IGFBP-2/α2M complexes most likely contributes to the regulation of IGFBP-2 proteolysis and, thus, the activity of IGFs.

Altered protein glycosylation as cancer biomarker can be effectively monitored by lectin-based protein microarray.

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