MHC Variants Associated With Symptomatic Versus Asymptomatic SARS-CoV-2 Infection in Highly Exposed Individuals

The role of inflammatory gene polymorphisms in severe COVID-19: a review

The COVID-19 pandemic, caused by the novel coronavirus SARS-CoV-2, has profoundly impacted global healthcare systems and spurred extensive research efforts over the past three years. One critical aspect of the disease is the intricate interplay between the virus and the host immune response, particularly the role of inflammatory gene expression in severe COVID-19. While numerous previous studies have explored the role of genetic polymorphisms in COVID-19, research specifically focusing on inflammatory genes and their associations with disease severity remains limited. This review explores the relationship between severe COVID-19 outcomes and genetic polymorphisms within key inflammatory genes. By investigating the impact of genetic variations on immune responses, which include cytokine production and downstream signalling pathways, we aim to provide a comprehensive overview of how genetic polymorphisms contribute to the variability in disease presentation. Through an in-depth analysis of existing literature, we shed light on potential therapeutic targets and personalized approaches that may enhance our understanding of disease pathogenesis and treatment strategies.

Potential protective role of interferon-induced protein with tetratricopeptide repeats 3 (IFIT3) in COVID-19

The COVID-19 pandemic has prompted a quest to understand why certain individuals remain uninfected or asymptomatic despite repetitive exposure to SARS-CoV-2. Here, we focused on six exposed females residing with their symptomatic and reinfected SARS-CoV-2 PCR-positive COVID-19 partners. Peripheral blood mononuclear cell samples from couples were analysed for poly (I:C)-induced mRNA expression of type I/III interferons and interferon-stimulated genes (ISGs). Remarkably, we found a significant upregulation of the ISG interferon-inducible protein with tetrapeptide repeats 3 (IFIT3) gene exclusively in exposed uninfected or asymptomatic females, suggesting a potential role in protective immunity against symptomatic COVID-19.

Unraveling the protective genetic architecture of COVID-19 in the Brazilian Amazon

Despite all the efforts acquired in four years of the COVID-19 pandemic, the path to a full understanding of the biological mechanisms involved in this disease remains complex. This is partly due to a combination of factors, including the inherent characteristics of the infection, socio-environmental elements, and the variations observed within both the viral and the human genomes. Thus, this study aimed to investigate the correlation between genetic host factors and the severity of COVID-19. We conducted whole exome sequencing (WES) of 124 patients, categorized into severe and non-severe groups. From the whole exome sequencing (WES) association analysis, four variants (rs1770731 in CRYBG1, rs7221209 in DNAH17, rs3826295 in DGKE, and rs7913626 in CFAP46) were identified as potentially linked to a protective effect against the clinical severity of COVID-19, which may explain the less severe impact of COVID-19 on the Northern Region. Our findings underscore the importance of carrying out more genomic studies in populations living in the Amazon, one of the most diverse from the point of view of the presence of rare and specific alleles. To our knowledge, this is the first WES study of admixed individuals from the Brazilian Amazon to investigate genomic variants associated with the clinical severity of COVID-19.

The MICA deletion across different populations

The MICA gene encodes a glycoprotein upregulated upon cellular stress, particularly in oxidative stress, intracellular infections, and tumorigenesis. This stress-signaling molecule interacts with the activating receptor NKG2D from Natural Killer (NK) and some T lymphocytes, stimulating their cytotoxic activity. MICA is encoded within the human Major Histocompatibility Complex next to the HLA-B locus and is highly polymorphic. MICA might be absent from chromosome 6 due to a large deletion of approximately 100 Kb between HLA-B and MICB. Therefore, some individuals may not produce any isoform of MICA. The distribution of this phenotype may vary among different populations. We evaluated the distribution of the MICA*del and other MICA null alleles in different biogeographic regions and the Linkage Disequilibrium (LD) pattern between this allele and HLA-B. We detected at least two different patterns of deletion, one with full deletion of MICA and surrounding sequences and one partial MICA deletion. The presence of different patterns of deletion suggests independent deletion events. We confirm that the previously described MICA*del allele is mainly associated with B*48 and MICB*009N in Asia and America, but other haplotypes also occur. While most samples with complete or partial MICA deletion are heterozygous and present one functional copy of both MICA and MICB genes, we detected two samples with no functional MICA and one with no functional MIC genes. Therefore, other mechanisms might be in place to compensate for the absence of MIC molecules.

Evaluation of HLA typing content of next-generation sequencing datasets from family trios and individuals of arab ethnicity

Introduction: HLA typing is a critical tool in both clinical and research applications at the individual and population levels. Benchmarking studies have indicated HLA-HD as the preferred tool for accurate and comprehensive HLA allele calling. The advent of next-generation sequencing (NGS) has revolutionized genetic analysis by providing high-throughput sequencing data. This study aims to evaluate, using the HLA-HD tool, the HLA typing content of whole exome, whole genome, and HLA-targeted panel sequence data from the consanguineous population of Arab ethnicity, which has been underrepresented in prior benchmarking studies. Methods: We utilized sequence data from family trios and individuals, sequenced on one or more of the whole exome, whole genome, and HLA-targeted panel sequencing technologies. The performance and resolution across various HLA genes were evaluated. We incorporated a comparative quality control analysis, assessing the results obtained from HLA-HD by comparing them with those from the HLA-Twin tool to authenticate the accuracy of the findings. Results: Our analysis found that alleles across 29 HLA loci can be successfully and consistently typed from NGS datasets. Clinical-grade whole exome sequencing datasets achieved the highest consistency rate at three-field resolution, followed by targeted HLA panel, research-grade whole exome, and whole genome datasets. Discussion: The study catalogues HLA typing consistency across NGS datasets for a large array of HLA genes and highlights assessments regarding the feasibility of utilizing available NGS datasets in HLA allele studies. These findings underscore the reliability of HLA-HD for HLA typing in underrepresented populations and demonstrate the utility of various NGS technologies in achieving accurate HLA allele calling.

The Influence of HLA Polymorphisms on the Severity of COVID-19 in the Romanian Population

In this study, we aimed to investigate whether specific HLA alleles found in patients from Romania and the Republic of Moldova were associated with the severity of COVID-19 infection and its associated mortality. We analyzed the HLA alleles at the -A, -B, -C, -DRB1, and -DQB1 loci in a cohort of 130 individuals with severe and extremely severe forms of COVID-19, including 44 individuals who died. We compared these findings to a control group consisting of individuals who had either not been diagnosed with COVID-19 or had experienced mild forms of the disease. Using multivariate logistic regression models, we discovered that the B*27 and B*50 alleles were associated with an increased susceptibility to developing a severe form of COVID-19. The A*33 and C*15 alleles showed potential for offering protection against the disease. Furthermore, we identified two protective alleles (A*03 and DQB1*02) against the development of extremely severe forms of COVID-19. By utilizing score statistics, we established a statistically significant association between haplotypes and disease severity (p = 0.021). In summary, this study provides evidence that HLA genotype plays a role in influencing the clinical outcome of COVID-19 infection.

Human genetic determinants of COVID-19 in Brazil: challenges and future plans

COVID-19 pandemic represented a worldwide major challenge in different areas, and efforts undertaken by the scientific community led to the understanding of some of the genetic determinants that influence the different COVID-19 outcomes. In this paper, we review the studies about the role of human genetics in COVID-19 severity and how Brazilian studies also contributed to those findings. Rare variants in genes related to Inborn Errors of Immunity (IEI) in the type I interferons pathway, and its phenocopies, have been described as being causative of severe outcomes. IEI and its phenocopies are present in Brazil, not only in COVID-19 patients, but also in autoimmune conditions and severe reactions to yellow fever vaccine. In addition, studies focusing on common variants and GWAS studies encompassing worldwide patients have found several loci associated with COVID-19 severity. A GWAS study including only Brazilian COVID-19 patients identified a new locus 1q32.1 associated with COVID-19 severity. Thus, more comprehensive studies considering the Brazilian genomic diversity should be performed, since they can help to reveal not only what are the genetic determinants that contribute to the different outcomes for COVID-19 in the Brazilian population, but in the understanding of human genetics in different health conditions.

Rare peptide anchors of HLA class I alleles contribute to the COVID-19 disease severity and T cell memory

Understanding how human leukocyte antigen (HLA) polymorphism affects both the susceptibility and severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection will help to identify individuals at higher risk to better manage and prioritize vaccination at the clinical level and explain the differences in epidemic trends in different regions at the epidemiological level. This study compared the frequencies of HLA class I alleles (HLA-A, B) in 214 coronavirus disease 2019 (COVID-19) patients with different disease severity and 35 healthy controls and analyzed the correlations between specific HLA alleles and disease severity and T cell memory. The results showed no significant difference in HLA allele frequencies between COVID-19 patients and healthy controls (P > 0.05). The allele HLA-B*13:02 was significantly correlated with the disease severity of COVID-19 patients (P = 0.006). After adjustment for age and disease severity, the T cell responses of COVID-19 convalescents with the allele HLA-B*40:01 may be lower at six months (P = 0.044) and 12 months (P = 0.069). Moreover, these results may be due to their rare peptide anchors by analyzing the binding peptide motifs of these HLA alleles. The study may be valuable for investigating the potential association of specific HLA alleles with SARS-CoV-2 infection.

Genetic Association Studies of MICB and PLCE1 with Severity of Dengue in Indonesian and Taiwanese Populations

Dengue is an arboviral disease that has spread globally and become a major public health concern. A small proportion of patients may progress from symptomatic dengue fever (DF) to dengue hemorrhagic fever (DHF) or dengue shock syndrome (DSS). Findings from a previous genome-wide association study (GWAS) demonstrated that variations in the major histocompatibility complex (MHC) class I chain-related B (MICB) and the phospholipase C epsilon 1 (PLCE1) genes were related to DSS in a Vietnamese population. This study investigated associations of variations in MICB (rs3132468) and PLCE1 (rs3740360, rs3765524) with dengue severity and thrombocytopenia in both the Indonesian and Taiwanese populations. We sampled 160 patients from the Indonesian population and 273 patients from the Taiwanese population. None of the patients had DSS in the Taiwanese population. Based on age demographics, we found that dengue is more prevalent among younger individuals in the Indonesian population, whereas it has a greater impact on adults in the Taiwanese population. Our results showed the association between MICB rs3132468 and DSS. In addition, an association was identified between PLCE1 rs3740360 and DHF in secondary dengue in Indonesian patients. However, there is no association of MICB or PLCE1 variants with thrombocytopenia. This study highlights the value of genetic testing, which might be included in the clinical pathway for specific patients who can be protected from severe dengue.

Novel role of immune-related non-coding RNAs as potential biomarkers regulating tumour immunoresponse via MICA/NKG2D pathway

Major histocompatibility complex class I related chain A (MICA) is an important and stress-induced ligand of the natural killer group 2 member D receptor (NKG2D) that is expressed in various tumour cells. Given that the MICA/NKG2D signalling system is critically embedded in the innate and adaptive immune responses, it is particularly involved in the surveillance of cancer and viral infections. Emerging evidence has revealed the important roles of non-coding RNAs (ncRNAs) including microRNAs (miRNAs), long noncoding RNAs (lncRNAs) and circular RNAs (circRNAs) in different cancer types. We searched for all relevant publications in the PubMed, Scopus and Web of Science database using the keywords ncRNA, MICA, NKG2D, cancer, and miRNAs. All relevant studies published from 2008 to the 2023 were retrieved and collated. Notably, we found that miRNAs can target to NKG2D mRNA and MICA mRNA 3'-untranslated regions (3'-UTR), leading to translation inhibition of NKG2D and MICA degradation. Several immune-related MICA/NKG2D pathways may be dysregulated in cancer with aberrant miRNA expressions. At the same time, the competitive endogenous RNA (ceRNA) hypothesis holds that circRNAs, lncRNAs, and mRNAs induce an abnormal MICA expression by directly targeting downstream miRNAs to mediate mRNA suppression in cancer. This review summarizes the novel mechanism of immune escape in the ncRNA-related MICA/NKG2D pathway mediated by NK cells and cancer cells. Moreover, we identified the miRNA-NKG2D, miRNA-MICA and circRNA/lncRNA/mRNA-miRNA-mRNA/MICA axis. Thus, we were particularly concerned with the regulation of mediated immune escape in the MICA/NKG2D pathway by ncRNAs as potential therapeutic targets and diagnostic biomarkers of immunity and cancer.

Role of NKG2D ligands and receptor in haploidentical related donor hematopoietic cell transplantation

The recurrence of malignancy after hematopoietic cell transplantation (HCT) is the primary cause of transplantation failure. The NKG2D axis is a powerful pathway for antitumor responses, but its role in the control of malignancy after HCT is not well-defined. We tested the hypothesis that gene variation of the NKG2D receptor and its ligands MICA and MICB affect relapse and survival in 1629 patients who received a haploidentical HCT for the treatment of a malignant blood disorder. Patients and donors were characterized for MICA residue 129, the exon 5 short tandem repeat (STR), and MICB residues 52, 57, 98, and 189. Donors were additionally defined for the presence of NKG2D residue 72. Mortality was higher in patients with MICB-52Asn relative to those with 52Asp (hazard ratio [HR], 1.83; 95% confidence interval [CI], 1.24-2.71; P = .002) and lower in those with MICA-STR mismatch than in those with STR match (HR, 0.66; 95% CI, 0.54-0.79; P = .00002). Relapse was lower with NKG2D-72Thr donors than with 72Ala donors (relapse HR, 0.57; 95% CI, 0.35-0.91; P = .02). The protective effects of patient MICB-52Asp with donor MICA-STR mismatch and NKG2D-72Thr were enhanced when all 3 features were present. The NKG2D ligand/receptor pathway is a transplantation determinant. The immunobiology of relapse is defined by the concerted effects of MICA, MICB, and NKG2D germ line variation. Consideration of NKG2D ligand/receptor pairings may improve survival for future patients.

MHC class I links with severe pathogenicity in C57BL/6N mice infected with SARS-CoV-2/BMA8

BACKGROUND

The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) causes non-symptomatic infection, mild influenza-like symptoms to pneumonia, severe acute respiratory distress syndrome, and even death, reflecting different clinical symptoms of viral infection. However, the mechanism of its pathogenicity remains unclear. Host-specific traits have a breakthrough significance for studying the pathogenicity of SARS-CoV-2. We previously reported SARS-CoV-2/BMA8, a mouse-adapted strain, was lethal to aged BALB/c mice but not to aged C57BL/6N mice. Here, we further investigate the differences in pathogenicity of BMA8 strain against wild-type aged C57BL/6N and BALB/c mice.

METHODS

Whole blood and tissues were collected from mice before and after BMA8 strain infection. Viral replication and infectivity were assessed by detection of viral RNA copies and viral titers; the degree of inflammation in mice was tested by whole blood cell count, ELISA and RT-qPCR assays; the pathogenicity of SARS-CoV-2/BMA8 in mice was measured by Histopathology and Immunohistochemistry; and the immune level of mice was evaluated by flow cytometry to detect the number of CD8⁺ T cells.

RESULTS

Our results suggest that SARS-CoV-2/BMA8 strain caused lower pathogenicity and inflammation level in C57BL/6N mice than in BALB/c mice. Interestingly, BALB/c mice whose MHC class I haplotype is H-2K^d showed more severe pathogenicity after infection with BMA8 strain, while blockade of H-2K^b in C57BL/6N mice was also able to cause this phenomenon. Furthermore, H-2K^b inhibition increased the expression of cytokines/chemokines and accelerated the decrease of CD8⁺ T cells caused by SARS-CoV-2/BMA8 infection.

CONCLUSIONS

Taken together, our work shows that host MHC molecules play a crucial role in the pathogenicity differences of SARS-CoV-2/BMA8 infection. This provides a more profound insight into the pathogenesis of SARS-CoV-2, and contributes enlightenment and guidance for controlling the virus spread.

Insight into the liver dysfunction in COVID-19 patients: Molecular mechanisms and possible therapeutic strategies

As of June 2022, more than 530 million people worldwide have become ill with coronavirus disease 2019 (COVID-19). Although COVID-19 is most commonly associated with respiratory distress (severe acute respiratory syndrome), meta-analysis have indicated that liver dysfunction also occurs in patients with severe symptoms. Current studies revealed distinctive patterning in the receptors on the hepatic cells that helps in viral invasion through the expression of angiotensin-converting enzyme receptors. It has also been reported that in some patients with COVID-19, therapeutic strategies, including repurposed drugs (mitifovir, lopinavir/ritonavir, tocilizumab, etc.) triggered liver injury and cholestatic toxicity. Several proven indicators support cytokine storm-induced hepatic damage. Because there are 1.5 billion patients with chronic liver disease worldwide, it becomes imperative to critically evaluate the molecular mechanisms concerning hepatotropism of COVID-19 and identify new potential therapeutics. This review also designated a comprehensive outlook of comorbidities and the impact of lifestyle and genetics in managing patients with COVID-19.

Immunogenetics of HLA-B: SNP, allele, and haplotype diversity in populations from different continents and ancestry backgrounds

HLA-B is among the most variable gene in the human genome. This gene encodes a key molecule for antigen presentation to CD8+ T lymphocytes and NK cell modulation. Despite the myriad of studies evaluating its coding region (with an emphasis on exons 2 and 3), few studies evaluated introns and regulatory sequences in real population samples. Thus, HLA-B variability is probably underestimated. We applied a bioinformatics pipeline tailored for HLA genes on 5347 samples from 80 different populations, which includes more than 1000 admixed Brazilians, to evaluate the HLA-B variability (SNPs, indels, MNPs, alleles, and haplotypes) in exons, introns, and regulatory regions. We observed 610 variable sites throughout HLA-B; the most frequent variants are shared worldwide. However, the haplotype distribution is geographically structured. We detected 920 full-length haplotypes (exons, introns, and untranslated regions) encoding 239 different protein sequences. HLA-B gene diversity is higher in admixed populations and Europeans while lower in African ancestry individuals. Each HLA-B allele group is associated with specific promoter sequences. This HLA-B variation resource may improve HLA imputation accuracy and disease-association studies and provide evolutionary insights regarding HLA-B genetic diversity in human populations.

Immunological evaluation of young unvaccinated patients with Turner syndrome after COVID-19

OBJECTIVES

The X-chromosome contains the largest number of immune-related genes, which play a major role in COVID-19 symptomatology and susceptibility. Here, we had a unique opportunity to investigate, for the first time, COVID-19 outcomes in six unvaccinated young Brazilian patients with Turner syndrome (TS; 45, X0), including one case of critical illness in a child aged 10 years, to evaluate their immune response according to their genetic profile.

METHODS

A serological analysis of humoral immune response against SARS-CoV-2, phenotypic characterization of antiviral responses in peripheral blood mononuclear cells after stimuli, and the production of cytotoxic cytokines of T lymphocytes and natural killer cells were performed in blood samples collected from the patients with TS during the convalescence period. Whole exome sequencing was also performed.

RESULTS

Our volunteers with TS showed a delayed or insufficient humoral immune response to SARS-CoV-2 (particularly immunoglobulin G) and a decrease in interferon-γ production by cluster of differentiation (CD)4+ and CD8+ T lymphocytes after stimulation with toll-like receptors 7/8 agonists. In contrast, we observed a higher cytotoxic activity in the volunteers with TS than the volunteers without TS after phorbol myristate acetate/ionomycin stimulation, particularly granzyme B and perforin by CD8+ and natural killer cells. Interestingly, two volunteers with TS carry rare genetic variants in genes that regulate type I and III interferon immunity.

CONCLUSION

Following previous reports in the literature for other conditions, our data showed that patients with TS may have an impaired immune response against SARS-CoV-2. Furthermore, other medical conditions associated with TS could make them more vulnerable to COVID-19.

Differential haplotype expression in class I MHC genes during SARS-CoV-2 infection of human lung cell lines

Introduction

Cell entry of SARS-CoV-2 causes genome-wide disruption of the transcriptional profiles of genes and biological pathways involved in the pathogenesis of COVID-19. Expression allelic imbalance is characterized by a deviation from the Mendelian expected 1:1 expression ratio and is an important source of allele-specific heterogeneity. Expression allelic imbalance can be measured by allele-specific expression analysis (ASE) across heterozygous informative expressed single nucleotide variants (eSNVs). ASE reflects many regulatory biological phenomena that can be assessed by combining genome and transcriptome information. ASE contributes to the interindividual variability associated with the disease. We aim to estimate the transcriptome-wide impact of SARS-CoV-2 infection by analyzing eSNVs.

Methods

We compared ASE profiles in the human lung cell lines Calu-3, A459, and H522 before and after infection with SARS-CoV-2 using RNA-Seq experiments.

Results

We identified 34 differential ASE (DASE) sites in 13 genes (HLA-A, HLA-B, HLA-C, BRD2, EHD2, GFM2, GSPT1, HAVCR1, MAT2A, NQO2, SUPT6H, TNFRSF11A, UMPS), all of which are enriched in protein binding functions and play a role in COVID-19. Most DASE sites were assigned to the MHC class I locus and were predominantly upregulated upon infection. DASE sites in the MHC class I locus also occur in iPSC-derived airway epithelium basal cells infected with SARS-CoV-2. Using an RNA-Seq haplotype reconstruction approach, we found DASE sites and adjacent eSNVs in phase (i.e., predicted on the same DNA strand), demonstrating differential haplotype expression upon infection. We found a bias towards the expression of the HLA alleles with a higher binding affinity to SARS-CoV-2 epitopes.

Discussion

Independent of gene expression compensation, SARS-CoV-2 infection of human lung cell lines induces transcriptional allelic switching at the MHC loci. This suggests a response mechanism to SARS-CoV-2 infection that swaps HLA alleles with poor epitope binding affinity, an expectation supported by publicly available proteome data.

Disentangling the common genetic architecture and causality of rheumatoid arthritis and systemic lupus erythematosus with COVID-19 outcomes: Genome-wide cross trait analysis and bidirectional Mendelian randomization study

Coronavirus Disease (COVID-19) may cause a dysregulation of the immune system and has complex relationships with multiple autoimmune diseases, including rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). However, little is known about their common genetic architecture. Using the latest data from COVID-19 host genetics consortium and consortia on RA and SLE, we conducted a genome-wide cross-trait analysis to examine the shared genetic etiology between COVID-19 and RA/SLE and evaluated their causal associations using bidirectional Mendelian randomization (MR). The cross-trait meta-analysis identified 23, 28, and 10 shared genetic loci for severe COVID-19, COVID-19 hospitalization, and SARS-CoV-2 infection with RA, and 14, 17, and 7 shared loci with SLE, respectively. Co-localization analysis identified five causal variants in TYK2, IKZF3, PSORS1C1, and COG6 for COVID-19 with RA, and four in CRHR1, FUT2, and NXPE3 for COVID-19 with SLE, involved in immune function, angiogenesis and coagulation. Bidirectional MR analysis suggested RA is associated with a higher risk of COVID-19 hospitalization, and COVID-19 is not related to RA or SLE. Our novel findings improved the understanding of the genetic etiology shared by COVID-19, RA and SLE, and suggested an increased risk of COVID-19 hospitalization in people with higher genetic liability to RA.

Relevance of HLA-DP/DQ and INF-λ4 Polymorphisms to COVID-19 Outcomes

Background: Single nucleotide polymorphisms provide information on individuals' potential reactions to environmental factors, infections, diseases, as well as various therapies. A study on SNPs that influence SARS-CoV-2 susceptibility and severity may provide a predictive tool for COVID-19 outcomes and improve the customized coronavirus treatment. Aim: To evaluate the role of human leukocyte antigens DP/DQ and IFNλ4 polymorphisms on COVID-19 outcomes among Egyptian patients. Participants and Methods: The study involved 80 patients with severe COVID-19, 80 patients with mild COVID-19, and 80 non-infected healthy volunteers. Genotyping and allelic discrimination of HLA-DPrs3077 (G/A), HLA-DQrs7453920 (A/G), and IFNλ4 rs73555604 (C/T) SNPs were performed using real-time PCR. Results: Ages were 47.9 ± 8, 44.1 ± 12.1, and 45.8 ± 10 years in severe, mild and non-infected persons. There was a statistically significant association between severe COVID-19 and male gender (p = 0.002). A statistically significant increase in the frequency of HLA-DPrs3077G, HLA-DQrs7453920A, and IFNλ4rs73555604C alleles among severe COVID-19 patients when compared with other groups (p < 0.001). Coexistence of these alleles in the same individual increases the susceptibility to severe COVID-19 by many folds (p < 0.001). Univariate and multivariate logistic regression analysis for the studied parameters showed that old age, male gender, non-vaccination, HLA-DQ rs7453920AG+AA, HLA-DPrs3077GA+GG, and IFNλ4rs73555604CT+CC genotypes are independent risk factors for severe COVID-19 among Egyptian patients. Conclusion: HLA-DQ rs7453920A, HLA-DPrs3077G, and IFNλ4rs73555604C alleles could be used as markers of COVID-19 severity.

Better safe than sorry-Whole-genome sequencing indicates that missense variants are significant in susceptibility to COVID-19

Undoubtedly, genetic factors play an important role in susceptibility and resistance to COVID-19. In this study, we conducted the GWAS analysis. Out of 15,489,173 SNPs, we identified 18,191 significant SNPs for severe and 11,799 SNPs for resistant phenotype, showing that a great number of loci were significant in different COVID-19 representations. The majority of variants were synonymous (60.56% for severe, 58.46% for resistant phenotype) or located in introns (55.77% for severe, 59.83% for resistant phenotype). We identified the most significant SNPs for a severe outcome (in AJAP1 intron) and for COVID resistance (in FIG4 intron). We found no missense variants with a potential causal function on resistance to COVID-19; however, two missense variants were determined as significant a severe phenotype (in PM20D1 and LRP4 exons). None of the aforementioned SNPs and missense variants found in this study have been previously associated with COVID-19.

The association of human leucocyte antigen (HLA) alleles with COVID-19 severity: A systematic review and meta-analysis

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.

COVID-19 and non-Hodgkin's lymphoma: A common susceptibility pattern?

OBJECTIVE

To explore the link between COVID-19 incidence, socio-economic covariates, and NHL incidence.

DESIGN

Ecological study design.

SETTING

Sardinia, Italy.

PARTICIPANTS

We used official reports on the total cases of COVID-19 in 2020, published data on NHL incidence, and socio-economic indicators by administrative unit, covering the whole regional population.

MAIN OUTCOMES AND MEASURES

We used multivariable regression analysis to explore the association between the natural logarithm (ln) of the 2020 cumulative incidence of COVID-19 and the ln-transformed NHL incidence in 1974-2003, weighing by population size and adjusting by socioeconomic deprivation and other covariates.

RESULTS

The cumulative incidence of COVID-19 increased in relation to past incidence of NHL (p < 0.001), socioeconomic deprivation (p = 0.006), and proportion of elderly residents (p < 0.001) and decreased with urban residency (p = 0.001). Several sensitivity analyses confirmed the finding of an association between COVID-19 and NHL.

CONCLUSION

This ecological study found an ecological association between NHL and COVID-19. If further investigation would confirm our findings, shared susceptibility factors should be investigated among the plausible underlying mechanisms.

Men are the main COVID-19 transmitters: behavior or biology?

Background

COVID-19 has affected millions of people worldwide. Clinical manifestations range from severe cases with lethal outcome to mild or asymptomatic cases. Although the proportion of infected individuals does not differ between sexes, men are more susceptible to severe COVID-19, with a higher risk of death than women. Also, men are pointed out as more lax regarding protective measures, mask wearing and vaccination. Thus, we questioned whether sex-bias may be explained by biological pathways and/or behavioral aspects or both.

Methods

Between July 2020 and July 2021, we performed an epidemiological survey including 1744 unvaccinated adult Brazilian couples, with there was at least one infected symptomatic member, who were living together during the COVID-19 infection without protective measures. Presence or absence of infection was confirmed by RT-PCR and/or serology results. Couples were divided into two groups: (1) both partners were infected (concordant couples) and (2) one partner was infected and the spouse remained asymptomatic despite the close contact with the COVID-19 symptomatic partner (discordant couples). Statistical analysis of the collected data was performed aiming to verify a differential transmission potential between genders in couples keeping contact without protective measures.

Results

The combination of our collected data showed that the man is the first (or the only) affected member in most cases when compared to women and that this difference may be explained by biological and behavioral factors.

Conclusions

The present study confirmed the existence of gender differences not only for susceptibility to infection and resistance to COVID-19 but also in its transmission rate.

There are sex differences in COVID-19 susceptibility and transmission between couples highly exposed to SARS-Cov-2 without protective measures;

Men are more efficient virus transmitters than women;

Sex-bias in COVID-19 transmission can be explained by differences in viral load in saliva, immune response and also behavioral protective differences between genders.

The oldest unvaccinated Covid-19 survivors in South America

BACKGROUND

Although older adults are at a high risk of severe or critical Covid-19, there are many cases of unvaccinated centenarians who had a silent infection or recovered from mild or moderate Covid-19. We studied three Brazilian supercentenarians, older than 110 years, who survived Covid-19 in 2020 before being vaccinated.

RESULTS

Despite their advanced age, humoral immune response analysis showed that these individuals displayed robust levels of IgG and neutralizing antibodies (NAbs) against SARS-CoV-2. Enrichment of plasma proteins and metabolites related to innate immune response and host defense was also observed. None presented autoantibodies (auto-Abs) to type I interferon (IFN). Furthermore, these supercentenarians do not carry rare variants in genes underlying the known inborn errors of immunity, including particular inborn errors of type I IFN.

CONCLUSION

These observations suggest that their Covid-19 resilience might be a combination of their genetic background and their innate and adaptive immunity.

MUC22, HLA-A, and HLA-DOB variants and COVID-19 in resilient super-agers from Brazil

Background

Although aging correlates with a worse prognosis for Covid-19, super elderly still unvaccinated individuals presenting mild or no symptoms have been reported worldwide. Most of the reported genetic variants responsible for increased disease susceptibility are associated with immune response, involving type I IFN immunity and modulation; HLA cluster genes; inflammasome activation; genes of interleukins; and chemokines receptors. On the other hand, little is known about the resistance mechanisms against SARS-CoV-2 infection. Here, we addressed polymorphisms in the MHC region associated with Covid-19 outcome in super elderly resilient patients as compared to younger patients with a severe outcome.

Methods

SARS-CoV-2 infection was confirmed by RT-PCR test. Aiming to identify candidate genes associated with host resistance, we investigated 87 individuals older than 90 years who recovered from Covid-19 with mild symptoms or who remained asymptomatic following positive test for SARS-CoV-2 as compared to 55 individuals younger than 60 years who had a severe disease or died due to Covid-19, as well as to the general elderly population from the same city. Whole-exome sequencing and an in-depth analysis of the MHC region was performed. All samples were collected in early 2020 and before the local vaccination programs started.

Results

We found that the resilient super elderly group displayed a higher frequency of some missense variants in the MUC22 gene (a member of the mucins' family) as one of the strongest signals in the MHC region as compared to the severe Covid-19 group and the general elderly control population. For example, the missense variant rs62399430 at MUC22 is two times more frequent among the resilient super elderly (p = 0.00002, OR = 2.24).

Conclusion

Since the pro-inflammatory basal state in the elderly may enhance the susceptibility to severe Covid-19, we hypothesized that MUC22 might play an important protective role against severe Covid-19, by reducing overactive immune responses in the senior population.

Transcriptome-wide summary data-based Mendelian randomization analysis reveals 38 novel genes associated with severe COVID-19

Severe COVID-19 has a poor prognosis, while the genetic mechanism underlying severe COVID-19 remains largely unknown. We aimed to identify genes that are potentially causally associated with severe COVID-19. We conducted a summary data-based Mendelian randomization (SMR) analysis using expression quantitative trait loci (eQTL) data from 49 different tissues as the exposure and three COVID-19-phenotypes (very severe respiratory confirmed COVID-19 [severe COVID-19], hospitalized COVID-19, and SARS-CoV-2 infection) as the outcomes. SMR using multiple SNPs was used as a sensitivity analysis to reduce false positive rate. Multiple testing was corrected using the false discovery rate (FDR) q-value. We identified 309 significant gene-trait associations (FDR q value < 0.05) across 46 tissues for severe COVID-19, which mapped to 64 genes, of which 38 are novel. The top five most associated protein-coding genes were Interferon Alpha and Beta Receptor Subunit 2 (IFNAR2), 2'-5'-Oligoadenylate Synthetase 3 (OAS3), mucin 1 (MUC1), Interleukin 10 Receptor Subunit Beta (IL10RB), and Napsin A Aspartic Peptidase (NAPSA). The potential causal genes were enriched in biological processes related to type I interferons, interferon-gamma inducible protein 10 production, and chemokine (C-X-C motif) ligand 2 production. In addition, we further identified 23 genes and 5 biological processes which are unique to hospitalized COVID-19, as well as 13 genes that are unique to SARS-CoV-2 infection. We identified several genes that are potentially causally associated with severe COVID-19. These findings improve our limited understanding of the mechanism of COVID-19 and shed light on the development of therapeutic agents for treating severe COVID-19.

Follow-up of young adult monozygotic twins after simultaneous critical coronavirus disease 2019: A case report

Background

The influence of the host genome on coronavirus disease 2019 (COVID-19) susceptibility and severity is supported by reports on monozygotic (MZ) twins where both were infected simultaneously with similar disease outcomes, including several who died due to the SARS-CoV-2 infection within days apart. However, successive exposures to pathogens throughout life along with other environmental factors make the immune response unique for each individual, even among MZ twins.

Case presentation and methods

Here we report a case of a young adult monozygotic twin pair, who caught attention since both presented simultaneously severe COVID-19 with the need for oxygen support despite age and good health conditions. One of the twins, who spent more time hospitalized, reported symptoms of long-COVID even 7 months after infection. Immune cell profile and specific responses to SARS-CoV-2 were evaluated as well as whole exome sequencing.

Conclusion

Although the MZ twin brothers shared the same genetic mutations which may be associated with their increased risk of developing severe COVID-19, their clinical progression was different, reinforcing the role of both immune response and genetics in the COVID-19 presentation and course. Besides, post-COVID syndrome was observed in one of them, corroborating an association between the duration of hospitalization and the occurrence of long-COVID symptoms.

Immune modulation as a consequence of SARS-CoV-2 infection

Erroneous immune responses in COVID-19 could have detrimental effects, which makes investigation of immune network underlying COVID-19 pathogenesis a requisite. This study aimed to investigate COVID-19 related alterations within the frame of innate and adaptive immunity. Thirty-four patients clinically diagnosed with mild, moderate and severe COVID-19 disease were enrolled in this study. Decreased ILC1 and increased ILC2 subsets were detected in mild and moderate patients compared to healthy controls. NK cell subsets and cytotoxic capacity of NK cells were decreased in severe patients. Moreover, CD3+ T cells were reduced in severe patients and a negative correlation was found between CD3+ T cells and D-dimer levels. Likewise, moderate and severe patients showed diminished CD3+CD8+ T cells. Unlike T and NK cells, plasmablast and plasma cells were elevated in patients and IgG and IgA levels were particularly increased in severe patients. Severe patients also showed elevated serum levels of pro-inflammatory cytokines such as TNF-α, IL-6 and IL-8, reduced intracellular IFN-γ and increased intracellular IL-10 levels. Our findings emphasize that SARS-CoV-2 infection significantly alters immune responses and innate and acquired immunity are differentially modulated in line with the clinical severity of the disease. Elevation of IL-10 levels in NK cells and reduction of CD3+ and CD8+ T cells in severe patients might be considered as a protective response against the harmful effect of cytokine storm seen in COVID-19.

Exome-Wide Association Study Reveals Host Genetic Variants Likely Associated with the Severity of COVID-19 in Patients of European Ancestry

Host genetic variability plays a pivotal role in modulating COVID-19 clinical outcomes. Despite the functional relevance of protein-coding regions, rare variants located here are less likely to completely explain the considerable numbers of acutely affected COVID-19 patients worldwide. Using an exome-wide association approach, with individuals of European descent, we sought to identify common coding variants linked with variation in COVID-19 severity. Herein, cohort 1 compared non-hospitalized (controls) and hospitalized (cases) individuals, and in cohort 2, hospitalized subjects requiring respiratory support (cases) were compared to those not requiring it (controls). 229 and 111 variants differed significantly between cases and controls in cohorts 1 and 2, respectively. This included FBXO34, CNTN2, and TMCC2 previously linked with COVID-19 severity using association studies. Overall, we report SNPs in 26 known and 12 novel candidate genes with strong molecular evidence implicating them in the pathophysiology of life-threatening COVID-19 and post-recovery sequelae. Of these few notable known genes include, HLA-DQB1, AHSG, ALOX5AP, MUC5AC, SMPD1, SPG7, SPEG,GAS6, and SERPINA12. These results enhance our understanding of the pathomechanisms underlying the COVID-19 clinical spectrum and may be exploited to prioritize biomarkers for predicting disease severity, as well as to improve treatment strategies in individuals of European ancestry.

Epigenetic profiling linked to multisystem inflammatory syndrome in children (MIS-C): A multicenter, retrospective study

BACKGROUND

Most children and adolescents infected with the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) remain asymptomatic or develop a mild coronavirus disease 2019 (COVID-19) that usually does not require medical intervention. However, a small proportion of pediatric patients develop a severe clinical condition, multisystem inflammatory syndrome in children (MIS-C). The involvement of epigenetics in the control of the immune response and viral activity prompted us to carry out an epigenomic study to uncover target loci regulated by DNA methylation that could be altered upon the appearance of MIS-C.

METHODS

Peripheral blood samples were recruited from 43 confirmed MIS-C patients. 69 non-COVID-19 pediatric samples and 15 COVID-19 pediatric samples without MIS-C were used as controls. The cases in the two groups were mixed and divided into discovery (MIS-C = 29 and non-MIS-C = 56) and validation (MIS-C = 14 and non-MIS-C = 28) cohorts, and balanced for age, gender and ethnic background. We interrogated 850,000 CpG sites of the human genome for DNA methylation variants.

FINDINGS

The DNA methylation content of 33 CpG loci was linked with the presence of MIS-C. Of these sites, 18 (54.5%) were located in described genes. The top candidate gene was the immune T-cell mediator ZEB2; and others highly ranked candidates included the regulator of natural killer cell functional competence SH2D1B; VWA8, which contains a domain of the Von Willebrand factor A involved in the pediatric hemostasis disease; and human leukocyte antigen complex member HLA-DRB1; in addition to pro-inflammatory genes such as CUL2 and AIM2. The identified loci were used to construct a DNA methylation profile (EPIMISC) that was associated with MIS-C in both cohorts. The EPIMISC signature was also overrepresented in Kawasaki disease patients, a childhood pathology with a possible viral trigger, that shares many of the clinical features of MIS-C.

INTERPRETATION

We have characterized DNA methylation loci that are associated with MIS-C diagnosis. The identified genes are likely contributors to the characteristic exaggerated host inflammatory response observed in these patients. The described epigenetic signature could also provide new targets for more specific therapies for the disorder.

FUNDING

Unstoppable campaign of Josep Carreras Leukaemia Foundation, Fundació La Marató de TV3, Cellex Foundation and CERCA Programme/Generalitat de Catalunya.

Natural Killer Cells in SARS-CoV-2 Infection: Pathophysiology and Therapeutic Implications

Natural Killer (NK) cells are lymphocytes of the innate immunity that play a crucial role in the control of viral infections in the absence of a prior antigen sensitization. Indeed, they display rapid effector functions against target cells with the capability of direct cell killing and antibody-dependent cell-mediated cytotoxicity. Furthermore, NK cells are endowed with immune-modulatory functions innate and adaptive immune responses via the secretion of chemokines/cytokines and by undertaking synergic crosstalks with other innate immune cells, including monocyte/macrophages, dendritic cells and neutrophils. Recently, the Coronavirus disease 2019 (COVID-19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has spread globally. Although the specific role of NK cells in COVID-19 pathophysiology still need to be explored, mounting evidence indicates that NK cell tissue distribution and effector functions could be affected by SARS-CoV-2 infection and that a prompt NK cell response could determine a good clinical outcome in COVID-19 patients. In this review, we give a comprehensive overview of how SARS-CoV-2 infection interferes with NK cell antiviral effectiveness and their crosstalk with other innate immune cells. We also provide a detailed characterization of the specific NK cell subsets in relation to COVID-19 patient severity generated from publicly available single cell RNA sequencing datasets. Finally, we summarize the possible NK cell-based therapeutic approaches against SARS-CoV-2 infection and the ongoing clinical trials updated at the time of submission of this review. We will also discuss how a deep understanding of NK cell responses could open new possibilities for the treatment and prevention of SARS-CoV-2 infection.

Major Histocompatibility Complex Class I Chain-Related α (MICA) STR Polymorphisms in COVID-19 Patients

The SARS-CoV-2 disease presents different phenotypes of severity. Comorbidities, age, and being overweight are well established risk factors for severe disease. However, innate immunity plays a key role in the early control of viral infections and may condition the gravity of COVID-19. Natural Killer (NK) cells are part of innate immunity and are important in the control of virus infection by killing infected cells and participating in the development of adaptive immunity. Therefore, we studied the short tandem repeat (STR) transmembrane polymorphisms of the major histocompatibility complex class I chain-related A (MICA), an NKG2D ligand that induces activation of NK cells, among other cells. We compared the alleles and genotypes of MICA in COVID-19 patients versus healthy controls and analyzed their relation to disease severity. Our results indicate that the MICA*A9 allele is related to infection as well as to symptomatic disease but not to severe disease. The MICA*A9 allele may be a risk factor for SARS-CoV-2 infection and symptomatic disease.

T Cell Epitope Discovery in the Context of Distinct and Unique Indigenous HLA Profiles

CD8+ T cells are a pivotal part of the immune response to viruses, playing a key role in disease outcome and providing long-lasting immunity to conserved pathogen epitopes. Understanding CD8+ T cell immunity in humans is complex due to CD8+ T cell restriction by highly polymorphic Human Leukocyte Antigen (HLA) proteins, requiring T cell epitopes to be defined for different HLA allotypes across different ethnicities. Here we evaluate strategies that have been developed to facilitate epitope identification and study immunogenic T cell responses. We describe an immunopeptidomics approach to sequence HLA-bound peptides presented on virus-infected cells by liquid chromatography with tandem mass spectrometry (LC-MS/MS). Using antigen presenting cell lines that stably express the HLA alleles characteristic of Indigenous Australians, this approach has been successfully used to comprehensively identify influenza-specific CD8+ T cell epitopes restricted by HLA allotypes predominant in Indigenous Australians, including HLA-A*24:02 and HLA-A*11:01. This is an essential step in ensuring high vaccine coverage and efficacy in Indigenous populations globally, known to be at high risk from influenza disease and other respiratory infections.

Mapping the epithelial-immune cell interactome upon infection in the gut and the upper airways

Increasing evidence points towards the key role of the epithelium in the systemic and over-activated immune response to viral infection, including SARS-CoV-2 infection. Yet, how viral infection alters epithelial-immune cell interactions regulating inflammatory responses, is not well known. Available experimental approaches are insufficient to properly analyse this complex system, and computational predictions and targeted data integration are needed as an alternative approach. In this work, we propose an integrated computational biology framework that models how infection alters intracellular signalling of epithelial cells and how this change impacts the systemic immune response through modified interactions between epithelial cells and local immune cell populations. As a proof-of-concept, we focused on the role of intestinal and upper-airway epithelial infection. To characterise the modified epithelial-immune interactome, we integrated intra- and intercellular networks with single-cell RNA-seq data from SARS-CoV-2 infected human ileal and colonic organoids as well as from infected airway ciliated epithelial cells. This integrated methodology has proven useful to point out specific epithelial-immune interactions driving inflammation during disease response, and propose relevant molecular targets to guide focused experimental analysis.

The 90 plus: longevity and COVID-19 survival

The world population is getting older and studies aiming to enhance our comprehension of the underlying mechanisms responsible for health span are of utmost interest for longevity and as a measure for health care. In this review, we summarized previous genetic association studies (GWAS) and next-generation sequencing (NGS) of elderly cohorts. We also present the updated hypothesis for the aging process, together with the factors associated with healthy aging. We discuss the relevance of studying older individuals and build databanks to characterize the presence and resistance against late-onset disorders. The identification of about 2 million novel variants in our cohort of more than 1000 elderly Brazilians illustrates the importance of studying highly admixed populations of non-European ancestry. Finally, the ascertainment of nonagenarians and particularly of centenarians who were recovered from COVID-19 or remained asymptomatic opens new avenues of research aiming to enhance our comprehension of biological mechanisms associated with resistance against pathogens.

Approaching Genetics Through the MHC Lens: Tools and Methods for HLA Research

The current SARS-CoV-2 pandemic era launched an immediate and broad response of the research community with studies both about the virus and host genetics. Research in genetics investigated HLA association with COVID-19 based on in silico, population, and individual data. However, they were conducted with variable scale and success; convincing results were mostly obtained with broader whole-genome association studies. Here, we propose a technical review of HLA analysis, including basic HLA knowledge as well as available tools and advice. We notably describe recent algorithms to infer and call HLA genotypes from GWAS SNPs and NGS data, respectively, which opens the possibility to investigate HLA from large datasets without a specific initial focus on this region. We thus hope this overview will empower geneticists who were unfamiliar with HLA to run MHC-focused analyses following the footsteps of the Covid-19|HLA & Immunogenetics Consortium.