Patients With Common Variable Immunodeficiency (CVID) Show Higher Gut Bacterial Diversity and Levels of Low-Abundance Genes Than the Healthy Housemates

Relation between dysbiosis and inborn errors of immunity

Inborn errors of immunity (IEI) disorders, formerly primary immune deficiency diseases, are a heterogeneous group of disorders with variable hereditary transitions, clinical manifestations, complications and varying disease severity. Many of the clinical symptoms, signs and complications in IEI patients can be attributed to inflammatory and immune dysregulatory processes due to loss of microbial diversity (dysbiosis). For example, in common variable immunodeficiency patients, the diversity of bacteria, but not fungi, in the gut microbiota has been found to be reduced and significantly altered. Again, this was associated with a more severe disease phenotype. Compromise of the STAT3/Th17 pathway in hyper-IgE syndrome may lead to dysbiosis of the oral microbiota in these patients, causing Candida albicans to switch from commensal to pathogenic. Modification of the microbiota can be used as a therapeutic approach in patients with IEI. Prebiotics, probiotics, postbiotics and fecal microbiota transplantation can be used to restore the balance of the gut microbiota and reduce pathogenicity in IEI patients. Clinical trials are currently underway to understand the impact of this dysbiosis on the phenotype of IEI diseases and its role in their treatment.

Possible Role of Cytomegalovirus in Gastric Cancer Development and Recurrent Macrolide-Resistant Campylobacter jejuni Infection in Common Variable Immunodeficiency: A Case Report and Literature Discussion

Common variable immunodeficiency (CVID) is the most common symptomatic immunodeficiency in adults. It comprises a group of syndromes whose etiology involves genetic, epigenetic, microbiota, and environmental factors. We present the case of a 46-year-old Caucasian male patient with CVID and an immune dysregulation phenotype. The particular elements of the case consisted of an atypical clinical course, which undoubtedly demonstrates the great variability of clinical manifestations that these types of patients can suffer from, including bacterial and viral infections, autoimmune phenomena, and neoplasia. Notably, the patient suffered from recurrent gastrointestinal infection with macrolide-resistant Campylobacter jejuni and gastroduodenal disease and viraemia by cytomegalovirus (CMV). In addition, CMV was postulated as the main pro-oncogenic factor contributing to the development of early-onset intestinal-type gastric adenocarcinoma, for which the patient underwent gastrectomy. The patient's evolution was difficult, but finally, as a result of the multidisciplinary approach, clinical stabilization and improvement in his quality of life were achieved. Based on our brief literature review, this is the first reported case of this clinical complexity. Our experience could help with the management of future patients with CVID and may also update current epidemiological data on CVID.

Association between the skin microbiome and MHC class II diversity in an amphibian

Microbiomes play an important role in determining the ecology and behaviour of their hosts. However, questions remain pertaining to how host genetics shape microbiomes, and how microbiome composition influences host fitness. We explored the effects of geography, evolutionary history and host genetics on the skin microbiome diversity and structure in a widespread amphibian. More specifically, we examined the association between bacterial diversity and composition and the major histocompatibility complex class II exon 2 diversity in 12 moor frog (Rana arvalis) populations belonging to two geographical clusters that show signatures of past and ongoing differential selection. We found that while bacterial alpha diversity did not differ between the two clusters, MHC alleles/supertypes and genetic diversity varied considerably depending on geography and evolutionary history. Bacterial alpha diversity was positively correlated with expected MHC heterozygosity and negatively with MHC nucleotide diversity. Furthermore, bacterial community composition showed significant variation between the two geographical clusters and between specific MHC alleles/supertypes. Our findings emphasize the importance of historical demographic events on hologenomic variation and provide new insights into how immunogenetic host variability and microbial diversity may jointly influence host fitness with consequences for disease susceptibility and population persistence.

Dysimmunity in common variable immunodeficiency is associated with alterations in oral, respiratory, and intestinal microbiota

Common variable immunodeficiency (CVID) is the most common symptomatic primary immunodeficiency characterized by decreased immunoglobulins and recurrent infections. Its aetiology remains unknown, and some patients present with severe non-infectious autoimmune or inflammatory complications with elevated associated morbimortality. Recently, intestinal dysbiosis has been proposed as a driver of immune dysregulation. In this study, we assessed the oral, respiratory, and gastrointestinal microbiota of 41 CVID patients (24 with dysimmune and 17 with infection complications) and 15 healthy volunteers using 16S rRNA gene sequencing to explore associations between microbiome profiles and CVID phenotypes. Profound differences in the composition of the microbiota in saliva, sputum, and stool were detected between dysimmune CVID patients and healthy individuals. Globally, respiratory species diversity and faecal bacterial richness were lower in CVID individuals with immune complications. Although a single species could not be identified as a robust predictor of dysimmunity, a combination of around 5-7 bacterial species in each type of sample could predict this severe phenotype with an accuracy of around 90% in the study population. Our study provides new insights into these previously unexplored but highly interrelated ecological niches among themselves and with patient profiles. Our data suggest that this disease-related systemic dysbiosis could be implicated in the immune dysregulation associated with severe cases of CVID.

Is there a role for microbiome-based approach in common variable immunodeficiency?

Common variable immunodeficiency (CVID) is a primary immunodeficiency characterized by low levels of serum immunoglobulins and increased susceptibility to infections, autoimmune disorders and cancer. CVID embraces a plethora of heterogeneous manifestations linked to complex immune dysregulation. While CVID is thought to be due to genetic defects, the exact cause of this immune disorder is unknown in the large majority of cases. Compelling evidences support a linkage between the gut microbiome and the CVID pathogenesis, therefore a potential for microbiome-based treatments to be a therapeutic pathway for this disorder. Here we discuss the potential of treating CVID patients by developing a gut microbiome-based personalized approach, including diet, prebiotics, probiotics, postbiotics and fecal microbiota transplantation. We also highlight the need for a better understanding of microbiota-host interactions in CVID patients to prime the development of improved preventive strategies and specific therapeutic targets.

Mendelian randomization analysis reveals causal relationships between gut microbiome and optic neuritis

BACKGROUND

It is unclear whether gut microbiota (GM) affects the risk of optic neuritis (ON) through the "gut-brain" axis and the "gut-retina" axis. To examine the causal relationship between GM and ON, we conducted Mendelian randomization (MR) study.

METHODS

Up to 18,340 samples of 24 population-based cohorts were included in genome-wide association study (GWAS) of 196 GM taxa. ON outcomes were selected from the FinnGen GWAS (951 ON cases and 307,092 controls). In addition, the GWAS based on UK Biobank (UKB) (105 ON cases and 456,243 controls) was used for further exploration. Inverse variance weighted (IVW) was carried out to estimate their effects on ON risk and the MR assumptions were evaluated in sensitivity analyses.

RESULTS

Among the 196 GM taxa, the IVW results confirmed that Family -Peptococcaceae (P = 2.17 × 10-3), Genus- Hungatella (P = 4.57 × 10-3) and genus-Eubacterium_rectale_group (P = 0.02) were correlated with the risk of ON based on Finngen GWAS. Based on data from UKB, Genus- Eubacterium_hallii_group (P = 1.50 × 10-3) and Genus- Ruminococcaceae_UCG_002 (P = 0.02) were correlated with the risk of ON. At the phylum, class and order levels, no GM taxa were causally related to ON (P > 0.05). Heterogeneity (P > 0.05) and pleiotropy (P > 0.05) analysis confirmed the robustness of the MR results.

CONCLUSION

Our MR findings support the causal effect of specific GM taxa on ON. GM may affect the risk of ON through the "gut-brain" axis and the "gut-retina" axis. However, further research is needed to confirm the relevant mechanism of the relationship between GM and ON.

Dysbiosis and primary B-cell immunodeficiencies: current knowledge and future perspective

According to Elie Metchnikoff, an originator of modern immunology, several pivotal functions for disease and health are provided by indigenous microbiota. Nonetheless, important mechanistic insights have been elucidated more recently, owing to the growing availability of DNA sequencing technology. There are 10 to 100 trillion symbiotic microbes (such as viruses, bacteria, and yeast) in each human gut microbiota. Both locally and systemically, the gut microbiota has been demonstrated to impact immune homeostasis. Primary B-cell immunodeficiencies (PBIDs) are a group of primary immunodeficiency diseases (PIDs) referring to the dysregulated antibody production due to either intrinsic genetic defects or failures in functions of B cells. Recent studies have found that PBIDs cause disruptions in the gut's typical homeostatic systems, resulting in inadequate immune surveillance in the gastrointestinal (GI) tract, which is linked to increased dysbiosis, which is characterized by a disruption in the microbial homeostasis. This study aimed to review the published articles in this field to provide a comprehensive view of the existing knowledge about the crosstalk between the gut microbiome and PBID, the factors shaping the gut microbiota in PBID, as well as the potential clinical approaches for restoring a normal microbial community.

Disturbed lipid profile in common variable immunodeficiency - a pathogenic loop of inflammation and metabolic disturbances

The relationship between metabolic and inflammatory pathways play a pathogenic role in various cardiometabolic disorders and is potentially also involved in the pathogenesis of other disorders such as cancer, autoimmunity and infectious diseases. Common variable immunodeficiency (CVID) is the most common primary immunodeficiency in adults, characterized by increased frequency of airway infections with capsulated bacteria. In addition, a large proportion of CVID patients have autoimmune and inflammatory complications associated with systemic inflammation. We summarize the evidence that support a role of a bidirectional pathogenic interaction between inflammation and metabolic disturbances in CVID. This include low levels and function of high-density lipoprotein (HDL), high levels of triglycerides (TG) and its major lipoprotein very low-density lipoprotein (VLDL), and an unfavorable fatty acid (FA) profile. The dysregulation of TG, VLDL and FA were linked to disturbed gut microbiota profile, and TG and VLDL levels were strongly associated with lipopolysaccharides (LPS), a marker of gut leakage in blood. Of note, the disturbed lipid profile in CVID did not include total cholesterol levels or high low-density lipoprotein levels. Furthermore, increased VLDL and TG levels in blood were not associated with diet, high body mass index and liver steatosis, suggesting a different phenotype than in patients with traditional cardiovascular risk such as metabolic syndrome. We hypothesize that these metabolic disturbances are linked to inflammation in a bidirectional manner with disturbed gut microbiota as a potential contributing factor.

Treatment of inflammatory complications in common variable immunodeficiency (CVID): current concepts and future perspectives

INTRODUCTION

Patients with Common variable immunodeficiency (CVID) have a high frequency of inflammatory complications like autoimmune cytopenias, interstitial lung disease and enteropathy. These patients have poor prognosis and effective, timely and safe treatment of inflammatory complications in CVID are essential, but guidelines and consensus on therapy are often lacking.

AREAS COVERED

This review will focus on current medical treatment of inflammatory complications in CVID and point out some future perspectives based on literature indexed in PubMed. There are a number of good observational studies and case reports on treatment of specific complications but randomized controlled trials are scarce.

EXPERT OPINION

In clinical practice, the most urgent issues that need to be addressed are the preferred treatment of GLILD, enteropathy and liver disease. Treating the underlying immune dysregulation and immune exhaustion in CVID is an alternative approach that potentially could alleviate these and other organ-specific inflammatory complications. Therapies of potential interest and wider use in CVID include mTOR-inhibitors like sirolimus, JAK-inhibitors like tofacitinib, the monoclonal IL-12/23 antibody ustekinumab, the anti-BAFF antibody belimumab and abatacept. For all inflammatory complications, there is a need for prospective therapeutic trials, preferably randomized controlled trials, and multi-center collaborations with larger cohorts of patients will be essential.

Common Variable Immunodeficiency Patient Fecal Microbiota Transplant Recapitulates Gut Dysbiosis

Purpose

Patients with non-infectious complications have worse clinical outcomes in common variable immunodeficiency (CVID) than those with infections-only. Non-infectious complications are associated with gut microbiome aberrations, but there are no reductionist animal models that emulate CVID. Our aim in this study was to uncover potential microbiome roles in the development of non-infectious complications in CVID.

Methods

We examined fecal whole genome shotgun sequencing from patients CVID, and non-infectious complications, infections-only, and their household controls. We also performed Fecal Microbiota transplant from CVID patients to Germ-Free Mice.

Results

We found potentially pathogenic microbes Streptococcus parasanguinis and Erysipelatoclostridium ramosum were enriched in gut microbiomes of CVID patients with non-infectious complications. In contrast, Fusicatenibacter saccharivorans and Anaerostipes hadrus, known to suppress inflammation and promote healthy metabolism, were enriched in gut microbiomes of infections-only CVID patients. Fecal microbiota transplant from non-infectious complications, infections-only, and their household controls into germ-free mice revealed gut dysbiosis patterns in recipients from CVID patients with non-infectious complications, but not infections-only CVID, or household controls recipients.

Conclusion

Our findings provide a proof of concept that fecal microbiota transplant from CVID patients with non-infectious complications to Germ-Free mice recapitulates microbiome alterations observed in the donors.

Gastrointestinal Involvement in Primary Antibody Deficiencies

Primary antibody deficiencies (PADs) are the most frequent group of inborn errors of immunity. Impaired B-cell development, reduced production of immunoglobulins (mainly IgG and IgA), and specific antibodies resulting in recurrent infections are their hallmarks. Infections typically affect the respiratory tract; however, gastrointestinal involvement is also common. These include infection with Helicobacter pylori, Salmonella, Campylobacter species, Giardia, and noroviruses. Impaired IgA production also contributes to dysbiosis and thereby an increase in abundance of species with proinflammatory properties, resulting in immune system dysregulation. Dysregulation of the immune system results in a broad spectrum of non-infectious manifestations, including autoimmune, lymphoproliferative, and granulomatous complications. Additionally, it increases the risk of malignancy, which may be present in more than half of patients with PADs. Higher prevalence is often seen in monogenic causes, and gastrointestinal involvement may clinically mimic various conditions including inflammatory bowel diseases and celiac disease but possess different immunological features and response to standard treatment, which make diagnosis and therapy challenging. The spectrum of malignancies includes gastric cancer and lymphoma. Thus, non-infectious manifestations significantly affect mortality and morbidity. In this overview, we provide a comprehensive insight into the epidemiology, genetic background, pathophysiology, and clinical manifestations of infectious and non-infectious complications.

Gut inflammation in CVID: causes and consequences

INTRODUCTION

There is a wide spectrum of noninfectious gastrointestinal pathology, causing considerable morbidity and mortality in CVID, where both etiology and effective therapy are under debate.

AREAS COVERED

This review will focus on the noninfectious inflammation in the GI tract in CVID patients, covering the both the upper and lower GI tract inflammation, including the liver. The controversy of the CVID enteropathy definition and that of gluten-free diet for celiac-like disease in CVID will be discussed. Furthermore, the review will cover the link between GI inflammation and GI cancer. Finally, the role of gut microbiota, IgA, and genetics and its relationship with CVID enteropathy is scrutinized. The authors reviewed literature from PubMed.

EXPERT OPINION

The heterogeneity and the unknown mechanism behind CVID enteropathy, and thereby the lack of effective treatment, is one of the key challenges in the field of CVID. Celiac-like disease in CVID is due to immune dysregulation, and a gluten-free diet is therefore not indicated. Gut microbial dysbiosis and mucosal IgA can initiate systemic and local inflammation and is involved in the immune dysregulation in CVID. Considering the heterogeneity of CVID enteropathy, personalized medicine is probably the future for these patients.

Gut Microbiome and Common Variable Immunodeficiency: Few Certainties and Many Outstanding Questions

Common variable immunodeficiency (CVID) is the most common symptomatic primary antibody immunodeficiency, characterized by reduced serum levels of IgG, IgA, and/or IgM. The vast majority of CVID patients have polygenic inheritance. Immune dysfunction in CVID can frequently involve the gastrointestinal tract and lung. Few studies have started to investigate the gut microbiota profile in CVID patients. Overall, the results suggest that in CVID patients there is a reduction of alpha and beta diversity compared to controls. In addition, these patients can exhibit increased plasma levels of lipopolysaccharide (LPS) and markers (sCD14 and sCD25) of systemic immune cell activation. CVID patients with enteropathy exhibit decreased IgA expression in duodenal tissue. Mouse models for CVID unsatisfactorily recapitulate the polygenic causes of human CVID. The molecular pathways by which gut microbiota contribute to systemic inflammation and possibly tumorigenesis in CVID patients remain poorly understood. Several fundamental questions concerning the relationships between gut microbiota and the development of chronic inflammatory conditions, autoimmune disorders or cancer in CVID patients remain unanswered. Moreover, it is unknown whether it is possible to modify the microbiome and the outcome of CVID patients through specific therapeutic interventions.

Systematic Feature Filtering in Exploratory Metabolomics: Application toward Biomarker Discovery

Exploratory mass spectrometry-based metabolomics generates a plethora of features in a single analysis. However, >85% of detected features are typically false positives due to inefficient elimination of chimeric signals and chemical noise not relevant for biological and clinical data interpretation. The data processing is considered a bottleneck to unravel the translational potential in metabolomics. Here, we describe a systematic workflow to refine exploratory metabolomics data and reduce reported false positives. We applied the feature filtering workflow in a case/control study exploring common variable immunodeficiency (CVID). In the first stage, features were detected from raw liquid chromatography-mass spectrometry data by XCMS Online processing, blank subtraction, and reproducibility assessment. Detected features were annotated in metabolomics databases to produce a list of tentative identifications. We scrutinized tentative identifications' physicochemical properties, comparing predicted and experimental reversed-phase liquid chromatography (LC) retention time. A prediction model used a linear regression of 42 retention indices with the cLogP ranging from -6 to 11. The LC retention time probes the physicochemical properties and effectively reduces the number of tentatively identified metabolites, which are further submitted to statistical analysis. We applied the retention time-based analytical feature filtering workflow to datasets from the Metabolomics Workbench (www.metabolomicsworkbench.org), demonstrating the broad applicability. A subset of tentatively identified metabolites significantly different in CVID patients was validated by MS/MS acquisition to confirm potential CVID biomarkers' structures and virtually eliminate false positives. Our exploratory metabolomics data processing workflow effectively removes false positives caused by the chemical background and chimeric signals inherent to the analytical technique. It reduced the number of tentatively identified metabolites by 88%, from initially detected 6940 features in XCMS to 839 tentative identifications and streamlined consequent statistical analysis and data interpretation.