IGHG3 hinge length variation was associated with the risk of critical disease and death in a Spanish COVID-19 cohort.

IgG3 would play an important role in the immune adaptive response against SARS-CoV-2, and low plasma levels might increase the risk of COVID-19 severity and mortality. The IgG3 hinge sequence has a variable repeat of a 15 amino acid exon with common 4-repeats (M) and 3-repeats (S). This length IGHG3 polymorphism might affect the IgG3 effector functions. The short hinge length would reduce the IgG3 flexibility and impairs the neutralization and phagocytosis compared to larger length-isoforms. We genotyped the IGHG3 length polymorphism in patients with critical COVID-19 (N = 516; 107 death) and 152 moderate-severe but no-critical cases. Carriers of the S allele had an increased risk of critical ICU and mortality (p < 0.001, OR = 2.79, 95% CI = 1.66-4.65). This adverse effect might be explained by a less flexibility and reduced ability to induce phagocytosis or viral neutralization for the short length allele. We concluded that the IgG3 hinge length polymorphism could be a predictor of critical COVID-19 and the risk of death. This study was based on a limited number of patients from a single population, and requires validation in larger cohorts.

Clinical differences between men and women with psoriatic arthritis: relevance of the analysis of genes and polymorphisms in the major histocompatibility complex region and of the age at onset of psoriasis.

It has been shown that males with spondyloarthritis tend to suffer from more severe spinal disease while females are more likely to have peripheral joint involvement. Nevertheless, gender-related differences have not been thoroughly explored in psoriatic arthritis (PsA). In PsA, males accumulate more peripheral and axial joint damage compared to women. However, it is not clear whether these findings are secondary to differences in occupational physical activity, hormonal changes, or other factors. The present study analyzed the differences in clinical expression of PsA between men and women. We have also evaluated the possible existence of gender-linked differences in the distribution of genes and polymorphisms within the major histocompatibility complex and whether patients' age at the onset of psoriasis established any differences in these aspects. Women suffered more polyarthritis, greater functional impairment, and a larger number of swollen joints during followup. We appreciated a differential expression of certain MHC genes according to gender and age at onset of psoriasis. Our results point to the need to include patient's age at the onset of psoriasis and gender as key stratification elements in future studies of genetic associations in PsA.

Patients with psoriatic arthritis may show differences in their clinical and genetic profiles depending on their age at psoriasis onset.

OBJECTIVES: The age of psoriasis onset has an important impact on the clinical expression and heritability of psoriasis. Psoriasis characteristics according to the age at disease onset have been extensively studied. However, the impact of the age of psoriasis onset on psoriatic arthritis (PsA) features has not been analysed in depth. The aim of the present paper is to analyse whether the age of psoriasis onset may have an impact on the clinical and genetic characteristics in a cohort of PsA patients. METHODS: The study included 110 PsA patients classified in accordance with the CASPAR criteria. Patients were divided into early (onset age <30 years) and late (onset age >30 years) onset psoriasis, and clinical features were studied in accordance to this stratification. Distribution of several genes within the MHC region were analysed in accordance with the prior stratification, and their frequencies compared to that of 110 healthy matched blood donors. RESULTS: Compared to patients with late-onset disease, PsA patients with early-onset psoriasis showed more frequently: a longer psoriasis-arthritis latency period (9.9±6 years vs. 3.8±4 years, p=0.0001), a positive family history of disease (60.3% vs. 20.5%, OR 6.1, 95% CI: 2.5-15.0, p=0.0001), severe psoriasis (PASI 8.2±4 vs. 3.6±2.2, p=0.0001), clinical enthesitis (37.7% vs. 22.4%, OR 2.09, 95% CI: 0.9-4.9, p=0.08), and oligoarthritis (47.5% vs. 28.6%, OR 2.26, 95% CI: 1.02-5.02, p=0.04). MICA-A9 was associated with susceptibility in both early-onset (60.7% vs. 30%, p=0.0002) and late-onset patients (59.2% vs. 30%, p=0.0008). However, HLA-Cw*0602 was significantly increased in patients with early-onset psoriasis (73.8% vs. 17%, p<0.0001), whereas the allele 384 of the microsatellite C1_4_4, located 34 kb telomeric to HLA-C locus, was increased only in late-onset cases (49% vs. 21%, p=0.001). CONCLUSIONS: Clinical and genetic features of PsA may differ depending on the age at psoriasis onset. This type of stratification should be considered in future genetic and epidemiological studies of PsA.

The origin of the bacterial immune response.

Bacteriophages are probably the oldest viruses, having appeared early during bacterial evolution. Therefore, bacteria and bacteriophages have a long history of co-evolution in which bacteria have developed multiple resistance mechanisms against bacteriophages. These mechanisms, that are very diverse and are in constant evolution, allow the survival of the bacteria. Bacteriophages have adapted to bacterial defense systems, devised strategies to evade these anti-phage mechanisms and restored their infective capacity. In this chapter, we review the bacterial strategies that hinder the phage infection as well as the counter-defense mechanisms developed.

Autophagy and self-defense.

Autophagy is a highly conserved mechanism which is essential for the maintenance of cellular homeostasis in response to cellular stress. Autophagy has been conserved from yeast to humans as a quality control process that is involved in the recognition and turnover of damaged proteins and organelles. It is also a response mechanism to nutrient starvation. In mammals, autophagy is involved in antigen presentation, tolerance, inflammation and protection against neurodegenerative diseases. The decrease of autophagy during aging reduces the removal of damaged organelles and increases the accumulation of waste products in the cells. In this chapter, we review these aspects of autophagy along with their role in self-nonself distinction, their implication in innate and adaptive immune response, and its dysregulation in the pathology of certain inflammatory and autoimmune diseases.

The emergence of the major histocompatilibility complex.

The Major Histocompatibility Complex (MHC) is a genomic region that contains genes that encode proteins involved with antigen presentation and, therefore, plays an important role in the adaptive immune system. The origin of these genes was probably an ancestral MHC that appeared before the emergence of the adaptive immune system and contained genes related to immunity. The organization of MHC genes varies in different groups of vertebrates; although, there are some characteristics that are maintained in all groups, which indicates that they confer some evolutionary advantage: Organization of the genes to form clusters and genetic polymorphisms. The study of how the MHC appeared during evolution and how it is organized in different species can help us clarify what features are essential in their participation in self-nonself recognition.

Association of the KIR3DS1*013 and KIR3DL1*004 alleles with susceptibility to ankylosing spondylitis.

OBJECTIVE: The killer cell immunoglobulin-like receptors (KIRs) form a group of regulatory molecules that specifically recognize HLA class I molecules. The aim of this study was to analyze the possible contribution of the KIR3DL1 and KIR3DS1 alleles, in addition to HLA-B27, in the susceptibility to ankylosing spondylitis (AS) in a population of individuals from Spain. METHODS: We genotyped the KIR3DS1 and KIR3DL1 alleles in 2 cohorts of patients with AS and healthy control subjects. In total, 270 patients with AS and 435 healthy, HLA-B27-positive matched control subjects from Spain were enrolled. The KIR3DS1 and KIR3DL1 alleles were genotyped by sequence-specific oligonucleotide probe-polymerase chain reaction, and their association with AS was analyzed. All individuals were typed for HLA-B. RESULTS: The KIR3DS1*013 allele was solely responsible for the increased frequency of the activator receptor KIR3DS1 in patients with AS compared with healthy HLA-B27-positive control subjects (35.7% versus 22.6% [P = 10(-6)], odds ratio 1.90, 95% confidence interval 1.50-2.40). The increased frequency of the KIR3DS1*013 allele in patients with AS was independent of the presence or absence of the HLA-Bw4I80 epitope. Moreover, the null allele KIR3DL1*004 was a unique inhibitory KIR3DL1 allele that showed a negative association with AS in the presence of HLA-Bw4I80. CONCLUSION: The increased frequency of the KIR3DS1*013 allele in patients with AS is clearly independent of the presence of the HLA-Bw4I80 epitope, whereas the presence of inhibitory allotypes such as KIR3DL1*004 demonstrated a negative association in patients with AS in the presence of HLA-Bw4I80. As a consequence, the influence of KIR genotypes on AS susceptibility would be mediated by a general imbalance between protective/inhibitory and risk/activating allotypes.

Genetic contribution of endoplasmic reticulum aminopeptidase 1 polymorphisms to liver fibrosis progression in patients with HCV infection.

The endoplasmic reticulum aminopeptidase ERAP1 regulates innate and adaptive immune responses, trimming peptides and loading onto HLA class I molecules. Coding single nucleotide polymorphisms within ERAP1 are associated with autoimmune diseases, viral infections, and cancer development. Our purpose was to analyze the influence of ERAP1 variants on fibrogenesis in hepatitis C virus (HCV)-infected patients. A range of ERAP1 polymorphisms were genotyped in 722 unrelated Caucasian patients diagnosed with chronic HCV from two Spanish cohorts. Patients were classified according to their fibrosis stage. Paraffin-embedded tissue microarrays were constructed to assess ERAP1 expression (HCV = 38; alcoholic = 20) by immunohistochemistry. A statistical algorithm was applied to derive a fibrogenesis prediction model. The ERAP1 variants rs30187/T (K528, pc < 0.001) and rs27044/G (Q730, pc < 0.001) were related with severe fibrosis. These results were validated in the two independent cohorts. Furthermore, patients with the rs30187/T allele had stronger ERAP1 protein expression than those with the rs30187/C (p < 0.05). The statistical model showed that patients with rs30187 C/T and T/T genotypes took 15.58 years (median) to develop advanced fibrosis, but this value was 32.08 years in patients carrying C/C genotype (p < 0.005). ERAP1 variants may influence the clinical course of fibrogenesis in HCV-infected patients. These polymorphisms could be exploited as constitutive new markers of fibrosis evolution. The results highlight the possibility of using modulators of ERAP1 to generate a protective immune response against chronic HCV infection. KEY MESSAGES: What is known Several ERAP1 polymorphisms are associated with autoimmune diseases and cancer. ERAP1 trims peptides to HLA class I presentation. What is new here ERAP1 polymorphisms are associated with fibrogenesis. The ERAP1 polymorphisms genotype could help us in clinical management of patients. Potential translational impact The use of modulators of ERAP1 could generate a protective response depending on SNPs.

Activating KIR genes are associated with ankylosing spondylitis in Asian populations.

Killer cell immunoglobulin-like receptors (KIRs) and human leukocyte antigen (HLA) loci are both highly polymorphic. The aim of this study was to perform a KIR genotype analysis and examine, in concert with HLA-B27 genotypes, their influence on ankylosing spondylitis (AS) susceptibility in two Asian populations (one from China, 42 patients and 30 controls, and another from Thailand, 30 patients and 16 controls). In the Chinese population, we observed an increase of KIR3DS1, KIR2DS5, and KIR2DL5 gene frequencies in AS patients (p(c) < 0.005, p(c) < 0.001, and p(c) < 0.01, respectively). A similar increase was reported in the Thai population: KIR3DS1, KIR2DS5, and KIR2DL5 gene frequencies were higher in AS (p(c) < 0.05, p < 0.05, and p(c) < 0.05, respectively). Upon analyzing the KIR3DL1/3DS1 genotypes, we determined significant differences in both populations. The frequency of 3DL1/3DL1 was decreased in AS (p(c) < 0.005 and p(c) < 0.05 in the Chinese and Thai populations, respectively), whereas 3DL1/3DS1 demonstrated an increased frequency in AS (p(c) < 0.005 in the Chinese population and p(c) < 0.05 in the Thai population).

Soluble MHC class I chain-related protein B serum levels correlate with disease activity in relapsing-remitting multiple sclerosis.

Recent studies demonstrated that dysregulation of NKG2D and its ligands, leading to activation of autoreactive effector cells, can trigger autoimmune diseases, but soluble forms of these ligands can downmodulate NKG2D expression in T effector cells. We investigated the presence of soluble major histocompatibility complex class I chain-related A or B (MICA or MICB) molecules in sera of multiple sclerosis (MS) patients and whether they play a role in the progression of the disease. Although soluble MICA serum levels did not differ, soluble MICB serum levels were higher in MS patients compared with controls. Moreover, the highest MICB levels were in MS patients during relapses. Using immunohistochemistry techniques, it was possible to locate MIC expression in neurons of MS demyelinating plaques that were intracellularly accumulated. Elevated soluble MICB levels exist in serum of multiple sclerosis patients related with disease activity. This may contribute to the modulation of immune response activity during relapses.

The allele MICB 0050204, over-represented in the Caucasian population, has an additional exon resulting from a new splice junction sequence.

We report that the allele MICB 0050204(1) allele, present in the majority of the Spanish population (70% of healthy controls) is characterized by the presence of an extra exon found between the sequence corresponding to exon 1 and 2. This is generated by a dinucleotide polymorphism in the first MICB intron that introduces a new splice junction, which can generate, by alternative splicing, transcripts with an additional exon. This new exon contains a premature stop codon and therefore the transcript does not produce a functional protein.

The predictive value of soluble major histocompatibility complex class I chain-related molecule A (MICA) levels on heart allograft rejection.

BACKGROUND: Recently the presence of a soluble form of major histocompatibility complex class I chain-related molecule A (sMICA) has been detected in the sera of patients with tumors. Shedding of sMICA by tumor cells downregulates NKG2D-mediated antitumor immunity. The aim of this investigation was to study the possible involvement of sMICA in the allograft acceptance after heart transplantation (HTX). METHODS: We monitored the levels of sMICA by specific enzyme-linked immunosorbent assay (ELISA) in a total of 146 serum samples obtained from 34 heart transplantation patients followed up during the first year post-HTX. RESULTS: The persistence of sMICA expression was correlated with the clinical evolution of these patients. sMICA was detected in the serum of 21 of 34 patients (61.70%) between 15 and 20 days after implantation and was practically absent in pretransplant serum samples. Twenty of these 21 patients (95.24%) with sMICA did not experience episodes of severe rejection during this period (P = 0.0001), whereas sMICA was practically absent in patients with manifestations of severe acute rejection. The longitudinal study of these patients revealed that the presence of sMICA was consistently maintained in 75% of the patients with good graft status during the period of observation. CONCLUSION: This has led us to believe that the presence of levels of sMICA during the first year post-HTX may contribute to allograft acceptance. Additionally, functional studies indicate that sMICA downregulates NKG2D surface expression, which may lead to a functional impairment of cell-mediated cytolysis. These data suggest a significant correlation between the presence of sMICA and a lower incidence of rejection.

MHC class I chain-related gene B promoter polymorphisms and celiac disease.

The possibility that susceptibility to celiac disease (CD) might be influenced by the MHC class I chain-related gene family, MICA and MICB, has been previously reported. In this study, we analyzed the MICB promoter and examined the association of the polymorphisms found within such in a group of CD patients. To study the MICB promoter we sequenced the 5' flanking region of MICB gene in DNA from homozygous B-lymphoblastoid cell lines corresponding to the most frequent MICB alleles found in our population (MICB*00502, MICB*002, MICB*004, and MICB*008). DNA from a MICB*003 homozygous individual was also analyzed. Sequence analysis revealed six single nucleotide polymorphisms located at positions 45860 C/A, 45862 G/C, 45877 C/G, 46113 A/C, 46219 G/C, and 46286 G/C and an insertion of 2 bp --/AG at position 45944 according to the published genomic sequence. Those polymorphisms were found to be associated in four different haplotypes corresponding to different MICB alleles. Subsequently, 126 CD subjects and 117 healthy controls were typed by polymerase chain reaction using sequence-specific primers for these polymorphisms. MICB promoter polymorphism haplotypes were also found in our population and showed strong linkage disequilibrium with MICB alleles. MICB promoter polymorphism Haplotype 3, included in MICB*002 and MICB*008 alleles, was found to be overrepresented in CD patients (79.4% CD patients vs 45.3% healthy controls; p(c) < 0.0001; OR = 4.64; CI 95% = 2.64-8.16). Both MICB*008 and MICB*002 alleles were found as part of the CD susceptibility extended haplotypes B8/DR3/DQ2, B18/DR3/DQ2, and DR4/DQ8.

The region of 150 kb telometic to HLA-C is associated with psoriasis in the Jewish population.

The HLA-Cw*0602 has been associated with psoriasis in different ethnic groups. But, it remains unclear whether HLA-C is the PSORS1 gene (the psoriasis gene in the MHC). Thus, several case-control studies have been performed in order to investigate whether HLA-C itself determines the susceptibility to the disease. We studied 59 Jewish patients with type I psoriasis and 79 matched controls. Polymorphic genes and markers from HLA-B (centromeric to HLA-C) to the corneodesmosin (CDSN) gene (telomeric to HLA-C) were genotyped in order to determine their contribution to the susceptibility to psoriasis. Neither HLA-Cw*0602 nor the allele CDSN*TTC were significantly associated with psoriasis with the size of the sample studied. The genes and markers telomeric to HLA-C such as the microsatellite C1_4_4 (OR = 2.6, 95% CI = 1.4-4.7, p(c) = 0.018) the octamer transcription factor (OTF)-3 gene (OR = 2.6, 95% CI = 1.6-4.3, p(c) = 0.0001) and the alpha-helix coiled-coil rod homologue (HCR) gene (OR = 2.5, 95% CI = 1.3-4.5, p(c) = 0.004), however, were associated with the disease. These results suggest that a major psoriasis susceptibility gene is likely to be located within a region of 150 kb telomeric to HLA-C and centromeric to the CDSN gene.

MHC class I chain-related gene A transmembrane polymorphism modulates the extension of ulcerative colitis.

Recent evidence from several studies has suggested a genetic predisposition in the pathogenesis of ulcerative colitis (UC), which is especially related with major histocompatibility complex (MHC) genes. The aim of this study was to investigate the possible association of human leukocyte antigen (HLA-B, HLA-DR) and MHC class I chain-related-transmembrane (MICA-TM) polymorphism with the behavior and extension of UC. We selected 121 unrelated patients with UC. These were divided into two groups according to the extension of the disease: 31 patients with distal UC and 90 with wide extension UC; 116 blood donors were also selected as healthy controls, all of whom were typed for HLA-B, HLA-DR, and MICA-TM alleles. HLA-B7 was found to be overrepresented in distal UC patients compared with those with extensive UC (p(c) = 0.007, OR = 5.33) and healthy controls (p(c) = 0.03, OR = 4.09). The MICA-A5.1 allele was also increased in distal UC (p(c) = 0.015, OR = 3.82) when compared with extensive forms. These alleles are in strong linkage disequilibrium in our population. The MICA-A5 allele was significantly increased in extensive forms when compared with healthy controls(p(c) = 0.02, OR = 2.4). According to our results, MICA-A5.1 allele seems to be protective against extensive forms of UC, and MICA-A5 may condition a worse progression of the disease. These results are in agreement with other studies that suggest a similar role of such alleles in other diseases, such as insulin-dependent diabetes mellitus and celiac disease.

High variability of HLA-B27 alleles in ankylosing spondylitis and related spondyloarthropathies in the population of northern Spain.

The distribution of B27 alleles (B*2701-23) was characterized by PCR-SSP in ankylosing spondylitis and related spondyloarthropathies (SpA) in a sample of B27 positive patients from northern Spain. Six B27 alleles were identified: B*2705,02,03,07,08 and B*2713. B*2705 and 02 were the most common alleles in the SpA studied: ankylosing spondylitis (AS) (n = 89), reactive arthritis (ReA) (n = 11), psoriatic arthritis (PsA) (n = 29), and inflammatory bowel disease (IBD) (n = 21). B*2707 and B*2708 were found in PsA patients and B*2703 in one patient with IBD. B*2713 was identified in a healthy control family. B*2713 has not been reported to be represented in either ethnic group. Thus, this population shows higher levels of B27 diversity than other Caucasian groups.

The Region Centromeric to HLA-C Is a Key Region for Understanding the Phenotypic Variability of Psoriatic Arthritis.

With the aim of clarifying the role of several polymorphisms around the HLA-C locus in the clinical expression of PsA, the distribution of several polymorphic markers and genes located around the HLA-C locus was analyzed in a well-established cohort of 110 patients with PsA, 50 patients with psoriasis alone, and 110 healthy controls. The frequency of these genes was also analyzed by PsA articular models, based on three main subgroups: oligoarthritis, polyarthritis, and spondylitis. Distal interphalangeal joint (DIP) involvement was associated with the presence of MICB-CA20 (OR 6.0, 95% CI: 1.58-22.69, P = 0.005). HLA-DRB∗07 was associated with oligoarticular forms of PsA (OR 4.1, 95% CI: 1.8-9.3, P = 0.0007). The spondylitic forms overexpressed the antigen HLA-B∗27 (OR 5.7, 95% CI: 2.4-13.6, P = 0.0001). MICA-A5.1 showed association with polyarthritis (OR 3.7, 95% CI: 1.5-8.8, P = 0.006). Genes telomeric to HLA-C were overexpressed in psoriasis but not in PsA subphenotypes. This study shows that the region centromeric to HLA-C is a key region that expresses not only disease risk genes but also genes that help explain the phenotypic variability of PsA.

Diversity of killer cell immunoglobulin-like receptor (KIR) genotypes and KIR2DL2/3 variants in HCV treatment outcome.

The aim of this study was to analyse the distribution of KIR haplotypes and the KIR2DL2/3 alleles in chronic HCV-infected patients in order to establish the influence on the response to pegylated interferon plus ribavirin classical treatment. The alleles study of previously associated KIR2DL2/3 showed that KIR2DL2*001 was more frequent in non-SVR (NSVR) (42.2% vs. 27.5%, p<0.05) and KIR2DL3*001 was associated with sustained viral response (SVR) (41.6% vs. 61.2%, p<0.005). The KIR2DL3*001-HLA-C1 association was also significant (24.5% vs. 45.7%, p<0.001). From the frequencies of KIR obtained, 35 genotypes were assigned on the basis of previous studies. The centromeric A/A genotype was more frequent in SVR (44.1% vs. 34.5%, p<0.005) and the centromeric B/B genotype was found to be significantly more frequent in NSVR (20.9% vs. 11.2%, p<0.001). The logic regression model showed the importance of KIR genes in predicting the response to combined treatment, since the positive predictive value (PPV) was improved (from 55.9% to 75.3%) when the analysis of KIR was included in addition to the IFNL3 rs12979860 polymorphism. The study of KIR receptors may be a powerful tool for predicting the combined treatment response in patients with chronic HCV infection in association with the determination of IFNL3 polymorphism.