ABSTRACT
COVID-19 has aspects on its pathogenesis that still need elucidating and an analysis of clinical and immunogenetic factors in each cohort of patients is paramount to understanding how genetic variability can explain the multiple clinical spectra seen in patients infected with SARS-CoV-2. The aim of this study was to correlate the KIR polymorphism/HLA class I ligand interactions from patients and healthy subjects with either the susceptibility or severity to COVID-19. Genotyping of HLA-A, -B, -C and KIR genes were carried out from 459 symptomatic as well as 667 non-infected Spanish Caucasian individuals using Lifecodes HLA-SSO and KIR-SSO kits (ImmucorTM, USA) and analyzed in the Luminex in this uni-centre case-control study performed at the University Hospital of Salamanca, Spain. Comparative KIR gene analysis showed that KIR2DS4 was significantly more representative in healthy versus infected individuals. When comparing subgroups of infected patients, KIR2DS3 had a higher frequency in those who progressed to a more severity disease and yet with higher mortality rate. Three functional combinations were significant on univariate analysis: KIR2DL2/C1, KIR2DS2/C1, and KIR2DS3/C1. However, in the multivariate analysis, only the KIR2DL2/C1 interaction remained significant (OR = 15.2 (95% CI 1.5-147), p = 0.0189). Compared with the solo-clinical characteristics predictive model, that included well-known comorbidity variables such as hypertension, age, sex, diabetes, C-reactive protein, dyslipidemia, smoking, ferritin, and fibrinogen, the clinical-and-KIR-based model showed a better ability to discriminate between severe and nonsevere patients with higher sensitivity and specificity. Our results support a fundamental role of KIR/ligand interaction in the clinical course of COVID-19. Since the KIR2DL2 gene has a high frequency in Spain (60%), the analysis of the KIR2DL2/C1 in symptomatic patients who require hospitalization could be helpful to better determine their prognosis.
ABSTRACT
A strong link between COVID-19 severity and HLAC* 04:01 allele has been replicated in several Caucasian populations including Armenians. The results have led to an idea that HLA-C*04:01 may affect the immune response via three biological mechanisms: (i) disruption of the HLA-C mediated protection harnessing natural killer cells (NK);(ii) causing NK hypo-responsiveness through KIR2DL1;or (iii) over-activation and exhaustion of CTL and NK cells by stimulating functional KIR2DS4. To test those hypotheses, we re-analyzed HLA-genotypes and RNA-sequencing data of Overmyer et al. [Cell Systems 2021;12:23-40]. An ordinal regression of patients' status (i.e., non-COVID vs. COVIDnon- ICU vs. COVID-ICU) against HLA-C has corroborated the increase in the disease severity with increasing HLA-C*04:01 dosage (p< 0.003). DESeq2 analyses of the transcriptome (16444 loci) within COVID subset mapped 3586 down-regulated and 4031 up-regulated loci to the disease severity at FDR p<0.05. The results of enrichment analyses of those 7617 genes indicated aberrations in processes, such as T cell activation, inflammatory response, positive regulation of both NK-mediated cytotoxicity and interferon-gamma production. However, only 563 down- and 341 up-regulated loci had nominally associated with the HLA-C*04:01 carriage, reflecting its genetic association with severe symptoms. Using GTEx data and rs5010528 as proxy for HLAC* 04:01 (R2 = 0.97, 1kG EUR cohort), we found that HLA-C*04:01 was associated with multiple tissue (e.g., lung, heart and blood) RNA expressional and splicing changes in >10 protein-coding loci situated close to HLA-C. The ontology analysis of the loci implicated HLA-C*04:01 in altering antigen processing and presentation of endogenous peptide antigen via HLA class I via ER pathway (FDR p<0.0001), protection from NKmediated cytotoxicity (p<0.004), and innate immune response to other organisms (p<0.009). The work was supported by the Science Committee of RA (grant E17).
ABSTRACT
During the first and second waves of coronavirus-19 disease, Sardinia had one of the lowest hospitalization and related mortality rates in Europe. However, in contrast with this evidence, the Sardinia population showed a very high frequency of the Neanderthal risk locus variant rs35044562, considered to be a major risk factor for a severe SARS-CoV-2 disease course. We evaluated 358 patients who had tested positive for SARS-CoV-2 and 314 healthy Sardinian controls (Italy). Patients were divided according to WHO classification: 120 patients asymptomatic, 90 pauci-symptomatic, 108 with a moderate disease course and 40 severely ill. The allele frequencies of Neanderthal-derived genetic variants reported as being protective (rs1156361) or causative (rs35044562) for severe illness were calculated in patients and controls. The Thalassemia variant (rs11549407), the HLA haplotypes, the KIR genes, as well as KIRs and their HLA class I ligand combinations were also investigated. The rs35044562 and rs1156361 Neanderthal variants revealed a distribution in Hardy-Weinberg equilibrium (HWE) both in SARS-CoV-2 patients and the control population (X2HWE = 0.82, p = 0.37 and X2HWE = 0.13, p = 0.72, respectively). Our findings reported an increased risk for severe disease in Sardinian patients carrying the rs35044562 high-risk variant [OR 5.32 (95% CI 2.53-12.01), p<0.0001]. Conversely, the protective effect of the HLA-A*02:01~B*18:01~DRB1*03:01 three-loci extended haplotype in the Sardinian population was shown to efficiently contrast the high risk of a severe and devastating outcome of the infection predicted for carriers of the Neanderthal locus [OR 15.47 (95% CI 5.8 - 41.0), p<0.0001]. This result suggests that the balance between risk and protective immunogenetic factors plays an important role in the evolution of COVID-19. A better understanding of these mechanisms may well turn out to be the biggest advantage in the race for the development of more efficient drugs and vaccines.
ABSTRACT
Extreme polymorphism of HLA and Killer-cell Immunoglobulin-like Receptors (KIR) differentiates immune responses across individuals. Additional to Tcell receptor interactions, subsets of HLA class I act as ligands for inhibitory and activating KIR, allowing natural killer (NK) cells to detect and kill infected cells. We investigated the impact of HLA and KIR polymorphism on the severity of COVID-19. High resolution HLA class I and II and KIR genotypes were determined from 403 non-hospitalized and 1,575 hospitalized SARS-CoV-2 infected patients from Italy collected in 2020. We observed that the activating KIR2DS4*001 allotype is associated with severe disease (OR = 3.74, 95% CI 1.75-9.29, pc = 0.003). KIR2DS4*001 in presence of its specific HLA ligands and inhibitory KIR3DL2*002 in absence its HLA ligand are also enriched in severe COVID-19 patients (OR = 1.64, 95% CI 1.09-2.50, p = 0.019), suggesting this combination acts in tandem to increase risk of developing severe COVID-19. We also observed the HLA class II allotype, HLA-DPB1*13:01 protects SARS-CoV-2 infected patients from hospitalization (OR = 0.49, 95% CI 0.33-0.74, pc = 0.019). These association analyses were replicated using logistic regression with sex and age as covariates. Autoantibodies against IFN-alpha associated with COVID-19 severity were detected in 26% of hospitalized patients. HLA-C*08:02 was more frequent in patients with IFN-alpha autoantibodies than those without, and KIR3DL1*01502 was only present in patients lacking IFN- alpha antibodies. We intend to expand this analysis in Greek and Spanish COVID-19 cohorts. These findings show that KIR and HLA polymorphism may play important roles in determining the clinical outcome following SARS-CoV-2 infection, by influencing the course both of innate and adaptive immunity.
ABSTRACT
BACKGROUND: The major histocompatibility complex (MHC) and the killer cell immunoglobulin-like receptors (KIR) are key regulators of immune responses. The cynomolgus macaque, an Old World monkey species, can be applied as an important preclinical model for studying human diseases, including coronavirus disease 2019 (COVID-19). Several MHC-KIR combinations have been associated with either a poor or good prognosis. Therefore, macaques with a well-characterized immunogenetic profile may improve drug evaluation and speed up vaccine development. At present, a complete overview of the MHC and KIR haplotype organizations in cynomolgus macaques is lacking, and characterization by conventional techniques is hampered by the extensive expansion of the macaque MHC-B region that complicates the discrimination between genes and alleles. METHODS: We assembled complete MHC and KIR genomic regions of cynomolgus macaque using third-generation long-read sequencing approach. We identified functional Mafa-B loci at the transcriptome level using locus-specific amplification in a cohort of 33 Vietnamese cynomolgus macaques. RESULTS: This is the first physical mapping of complete MHC and KIR gene regions in a Vietnamese cynomolgus macaque. Furthermore, we identified four functional Mafa-B loci (B2, B3, B5, and B6) and showed that alleles of the Mafa-I*01, -B*056, -B*034, and -B*001 functional lineages, respectively, are highly frequent in the Vietnamese cynomolgus macaque population. CONCLUSION: The insights into the MHC and KIR haplotype organizations and the level of diversity may refine the selection of animals with specific genetic markers for future medical research.