A large-scale investigation into the role of classical HLA loci in multiple types of severe infections, with a focus on overlaps with autoimmune and mental disorders

The expanding spectrum of infectious risk organisms and immunogenetic susceptibility in neuropsychiatric disorders

The spectrum of infectious risk organisms showing associations with psychiatric traits is expanding. Infectious agents can modulate the risk of psychiatric disorders at different stages of life, such as gestational, childhood, adolescent, and adult periods. Prenatal infection appears to 'prime' the developing brain, whereas infection during childhood or later periods may act as a 'second hit', and these may have synergistic effects on the risk of developing psychiatric diseases. However, neither all the individuals with antecedent infection develop psychiatric disorders, nor do infectious organisms alone lead to psychiatric phenotypes. This suggests modulatory effects of additional host factors. The host genetic background crucially determines differential susceptibility to infection and serves as an important gateway for immune activation and signalling, as well as homeostatic brain functions. Despite the presence of several immune checkpoints and effectors, the infectious organisms disrupt the balance between immune-activating and immune-compensatory mechanisms and contribute to immune dysregulation. This depends substantially on genetic loci encoding immune molecules such as Toll-like receptors, Major Histocompatibility Complex, cytokines/ chemokines and their receptors, complement proteins, and other molecules and elements such as human endogenous retroviruses and gut microbiome that have distinct roles in immune regulation and immune effector functions. Genetic variations within these loci not only influence differential susceptibility to infection but also confer risk to psychiatric disorders. This article highlights a comprehensive overview of the nexus between infections and immune function-related genes and their impact on psychiatric traits. Understanding such interactions will lead to the identification of genetic markers of susceptibility to infection and psychiatric diseases.

mRNA-miRNA integration analysis of T-cell exhaustion in sepsis from community-acquired pneumonia

Aim

Community-acquired pneumonia is an acute lung infection in patients without recent healthcare exposure that can progress to severe sepsis. Despite the well-established influence of miRNAs on inflammation, their specific roles in pneumonia-associated sepsis remain underexplored. In this pilot study, we aimed to provide insights into the pathogenesis of community-acquired pneumonia-associated sepsis by performing an integrative mRNA-miRNA analysis to identify key cellular signaling pathways and potential molecular targets for future research and treatment development.

Methods

We conducted a prospective, observational, single-center study including 14 critically ill patients with community-acquired pneumonia-associated sepsis and 15 healthy controls (median age: 78 [interquartile range 67.3-83.5] and 55 [interquartile range 40.5-59.0] years, respectively).

Results

Eleven patients required ventilatory support, and six met the diagnostic criteria for septic shock. All patients survived. RNA sequencing revealed 1209 upregulated and 1461 downregulated differentially expressed genes for mRNAs (false discovery rate < 0.05, |log2 fold change| >1.2), 51 upregulated and 21 downregulated genes for miRNAs, and 646 upregulated and 1274 downregulated for mRNA related to miRNAs. Canonical pathway analysis revealed activation of the programmed death-1/programmed death-ligand-1 cancer immunotherapy pathway and suppression of the Th1 pathway, indicating T-cell exhaustion in the acute phase of community-acquired pneumonia-associated sepsis.

Conclusion

This study provides valuable insights into the molecular mechanisms underlying CAP-associated sepsis, confirming the occurrence of immune dysregulation, particularly T-cell exhaustion. Our findings suggest that specific miRNAs and signaling pathways identified here may serve as potential therapeutic targets or biomarkers.

Multi-omics analysis reveals the interplay between pulmonary microbiome and host in immunocompromised patients with sepsis-induced acute lung injury

The mechanisms behind the high inflammatory state and immunocompromise in severe sepsis remain unclear. While microbiota's role in immune regulation is known, the impact of pulmonary microbiota on sepsis progression is not fully understood. This study aims to investigate pulmonary microbial characteristics in septic patients and their relationship with host immune-related genes and clinical features. Fifty-four sepsis patients were divided into the immunocompromised host (ICH) group (n = 18) and the control group (n = 36). Bronchoalveolar lavage fluid (BALF) was analyzed using metagenomic next-generation sequencing (mNGS) to assess the pulmonary microbiome, and transcriptomic sequencing evaluated host gene expression. The pulmonary microbiota network in the ICH group showed notable alterations. Symbiotic bacteria like Streptococcus salivarius and Streptococcus oralis were key taxa in the control group. In contrast, opportunistic pathogens such as Campylobacter concisus and Prevotella melaninogenica, typically linked to infections in various body sites, dominated in the ICH group. Transcriptomic analysis revealed differential genes between the two groups. The downregulated differential genes in the ICH group were primarily enriched in pathways related to T-cell activation and the Type I interferon signaling pathway, both crucial for the immune system. Further correlation analysis identified significant associations between certain microbes and host genes, as well as clinical indicators, particularly with species like Campylobacter concisus, Streptococcus salivarius, Streptococcus oralis, and several species of Veillonella. These findings suggest that alterations in the pulmonary microbiome, especially the presence of opportunistic pathogens, may contribute to immune dysregulation in immunocompromised septic patients, warranting further research to explore causal relationships.

IMPORTANCE

Recent research has substantiated the significant role of microbiota in immune regulation, which could influence high inflammatory state and immunocompromise in patients with severe sepsis, as well as provide new opportunities for acute lung injury induced by sepsis diagnosis and treatment. Our study identified some potential critical microbes (Campylobacter concisus and several species of Veillonella), which were correlated with immune-related genes and might be the novel target to regulate immunotherapy in sepsis.

Influence of polymorphic variations of IFNL, HLA, and IL-6 genes in severe cases of COVID-19

The administration of vaccination doses to the global population has led to a decrease in the incidence of COVID-19. However, the clinical picture developed by infected individuals remains extremely concerning due to the great variability in the severity of cases even in vaccinated individuals. The clinical progression of the pathology is characterized by various influential factors such as sex, age group, comorbidities, and the genetics of the individual. The immune response to viral infections can be strongly influenced by the genetics of individuals; nucleotide variations called single-nucleotide polymorphisms (SNPs) in structures involved in the innate and adaptive immune response such as interferon (IFN)-λ, human leukocyte antigen (HLA), and interleukin (IL)-6 are frequently associated with pathological progression. In this study, we conducted a review of the main SNPs of these structures that are associated with severity in COVID-19. Searches were conducted on some platforms of the National Center for Biotechnology and Information (NCBI), and 102 studies were selected for full reading according to the inclusion criteria. IFNs showed a strong association with antiviral function, specifically, IFN-λ3 (IL-28B) demonstrated genetic variants commonly related to clinical progression in various pathologies. For COVID-19, rs12979860 and rs1298275 presented frequently described unfavorable genotypes for pathological conditions of hepatitis C and hepatocellular carcinoma. The high genetic variability of HLA was reported in the studies as a crucial factor relevant to the late immune response, mainly due to its ability to recognize antigens, with the HLA-B*46:01 SNP being associated with susceptibility to COVID-19. For IL-6, rs1554606 showed a strong relationship with the clinical progression of COVID-19. In addition, rs2069837 was identified with possible host protection relationships when linked to this infection.

An immunogenetic investigation of 30 autoimmune and autoinflammatory diseases and their links to psychiatric disorders in a nationwide sample

Autoimmune and autoinflammatory diseases (AIIDs) involve a deficit in an individual's immune system function, whereby the immune reaction is directed against self-antigens. Many AIIDs have a strong genetic component, but they can also be triggered by environmental factors. AIIDs often have a highly negative impact on the individual's physical and mental wellbeing. Understanding the genetic underpinning of AIIDs is thus crucial both for diagnosis and for identifying individuals at high risk of an AIID and mental illness as a result thereof. The aim of the present study was to perform systematic statistical and genetic analyses to assess the role of human leukocyte antigen (HLA) alleles in 30 AIIDs and to study the links between AIIDs and psychiatric disorders. We leveraged the Danish iPSYCH Consortium sample comprising 65 534 individuals diagnosed with psychiatric disorders or selected as part of a random population sample, for whom we also had genetic data and diagnoses of AIIDs. We employed regression analysis to examine comorbidities between AIIDs and psychiatric disorders and associations between AIIDs and HLA alleles across seven HLA genes. Our comorbidity analyses showed that overall AIID and five specific AIIDs were associated with having a psychiatric diagnosis. Our genetic analyses found 81 significant associations between HLA alleles and AIIDs. Lastly, we show connections across AIIDs, psychiatric disorders and infection susceptibility through network analysis of significant HLA associations in these disease classes. Combined, our results include both novel associations as well as replications of previously reported associations in a large sample, and highlight the genetic and epidemiological links between AIIDs and psychiatric disorders.

Maternal pregnancy-related infections and autism spectrum disorder-the genetic perspective

Autism spectrum disorder (ASD) refers to a group of neurodevelopmental disorders which include deficits in behavior, social interaction and communication. ASD has a complex genetic architecture, and it is also influenced by certain environmental exposures. Both types of predisposing factors may be related to immunological mechanisms, involving, for example, immune system genes and infections. Past studies have shown an association between infections occurring during the pregnancy in the mother and increased risk of ASD in the child, an observation which has received recent support from experimental animal studies of ASD-like behavior. The aim of this study was to study the genetic contribution to this effect. We employed genetic correlation analyses across potential ASD subtypes stratified on the basis of maternal pregnancy-related infections within the iPSYCH ASD case-cohort sample, as well as a case-case GWAS. We validated the trends of the genetic correlation analyses observed in our sample using GWAS summary statistics from the PGC ASD study (excluding iPSYCH). The genetic correlation between ASD with a history of maternal pregnancy-related infections and ASD without a history of maternal infections in iPSYCH was rg = 0.3811. We obtained a similar estimate between the former and the PGC ASD phenotype (rg = 0.3997). Both estimates are lower compared to the genetic correlation between ASD without a history of maternal infections and the PGC ASD phenotype (rg = 0.6735), and between ASD with a history of maternal infections occurring only more than 2 months following childbirth and the PGC ASD phenotype (rg = 0.6293). Additionally, we observed genetic variance between the two main ASD phenotypes using summary statistics from the case-case GWAS in iPSYCH (h2cc = 0.1059), indicating genome-wide differences between the phenotypes. Our results suggest potentially different etiologies of ASD based on a history of maternal pregnancy-related infections, which may, in part, be genetic. This highlights the relevance of maternal pregnancy-related infections to genetic studies of ASD and provides new insights into the molecular underpinnings of ASD.