Mendelian susceptibility to mycobacterial disease: recent discoveries

Inherited human ITK deficiency impairs IFN-γ immunity and underlies tuberculosis

Inborn errors of IFN-γ immunity can underlie tuberculosis (TB). We report three patients from two kindreds without EBV viremia or disease but with severe TB and inherited complete ITK deficiency, a condition associated with severe EBV disease that renders immunological studies challenging. They have CD4+ αβ T lymphocytopenia with a concomitant expansion of CD4-CD8- double-negative (DN) αβ and Vδ2- γδ T lymphocytes, both displaying a unique CD38+CD45RA+T-bet+EOMES- phenotype. Itk-deficient mice recapitulated an expansion of the γδ T and DN αβ T lymphocyte populations in the thymus and spleen, respectively. Moreover, the patients' T lymphocytes secrete small amounts of IFN-γ in response to TCR crosslinking, mitogens, or forced synapse formation with autologous B lymphocytes. Finally, the patients' total lymphocytes secrete small amounts of IFN-γ, and CD4+, CD8+, DN αβ T, Vδ2+ γδ T, and MAIT cells display impaired IFN-γ production in response to BCG. Inherited ITK deficiency undermines the development and function of various IFN-γ-producing T cell subsets, thereby underlying TB.

Disseminated multidrug-resistant tuberculosis and SARS-CoV-2 co-infection in a child with IL-12Rβ1 deficiency

Mendelian Susceptibility to Mycobacterial Disease describes a spectrum of inherited defects, of which complete deficiency of the interleukin-12 receptor β subunit 1 (IL-12Rβ1) is the most common cause. This condition results in a predisposition to severe disease caused by mycobacteria. We report a case of disseminated multidrug-resistant tuberculosis with extensive central nervous system affection with SARS-CoV-2 co-infection, in a 4-year-old child with IL-12Rβ1 complete deficiency.

Mendelian Susceptibility to Mycobacterial Disease: Retrospective Clinical and Genetic Study in Mexico

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare genetic disorder characterized by impaired immunity against intracellular pathogens, such as mycobacteria, attenuated Mycobacterium bovis-Bacillus Calmette-Guérin (BCG) vaccine strains, and environmental mycobacteria in otherwise healthy individuals. Retrospective study reviewed the clinical, immunological, and genetic characteristics of patients with MSMD in Mexico. Overall, 22 patients diagnosed with MSMD from 2006 to 2021 were enrolled: 14 males (64%) and eight females. After BCG vaccination, 12 patients (70%) developed BCG infection. Furthermore, 6 (22%) patients developed bacterial infections mainly caused by Salmonella, as what is described next in the text is fungal infections, particularly Histoplasma. Seven patients died of disseminated BCG disease. Thirteen different pathogenic variants were identified in IL12RB1 (n = 13), IFNGR1 (n = 3), and IFNGR2 (n = 1) genes. Interleukin-12Rβ1 deficiency is the leading cause of MSMD in our cohort. Morbidity and mortality were primarily due to BCG infection.

Gene-environment interactions in birth defect etiology: Challenges and opportunities

Birth defects are relatively common congenital outcomes that significantly impact affected individuals, their families, and communities. Effective development and deployment of prevention and therapeutic strategies for these conditions requires sufficient understanding of etiology, including underlying genetic and environmental causes. Tremendous progress has been made in defining the genetic basis of familial and syndromic forms of birth defects. However, the majority of birth defect cases are considered nonsyndromic and thought to result from multifactorial gene-environment interactions. While substantial advances have been made in elucidating the genetic landscape of these etiologically complex conditions, significant biological and technical constraints have stymied progress toward a refined knowledge of environmental risk factors. Defining specific gene-environment interactions in birth defect etiology is even more challenging. However, progress has been made, including demonstration of critical proofs of concept and development of new conceptual and technical approaches for resolving complex gene-environment interactions. In this review, we discuss current views of multifactorial birth defect etiology, comparing them with other diseases that also involve gene-environment interactions, including primary immunodeficiency and cancer. We describe how various model systems have illuminated mechanisms of multifactorial etiology and these models' individual strengths and weaknesses. Finally, suggestions for areas of future emphasis are proposed.

The lung in inborn errors of immunity: From clinical disease patterns to molecular pathogenesis

In addition to being a vital organ for gas exchange, the lung is a crucial immune organ continuously exposed to the external environment. Genetic defects that impair immune function, called inborn errors of immunity (IEI), often have lung disease as the initial and/or primary manifestation. Common types of lung disease seen in IEI include infectious complications and a diverse group of diffuse interstitial lung diseases. Although lung damage in IEI has been historically ascribed to recurrent infections, contributions from potentially targetable autoimmune and inflammatory pathways are now increasingly recognized. This article provides a practical guide to identifying the diverse pulmonary disease patterns in IEI based on lung imaging and respiratory manifestations, and integrates this clinical information with molecular mechanisms of disease and diagnostic assessments in IEI. We cover the entire IEI spectrum, including immunodeficiencies and immune dysregulation with monogenic autoimmunity and autoinflammation, as well as recently described IEI with pulmonary manifestations. Although the pulmonary manifestations of IEI are highly relevant for all age groups, special emphasis is placed on the pediatric population, because initial presentations often occur during childhood. We also highlight the pivotal role of genetic testing in the diagnosis of IEI involving the lungs and the critical need to develop multidisciplinary teams for the challenging evaluation of these rare but potentially life-threatening disorders.

Host-directed immunotherapy to fight infectious diseases

PURPOSE OF REVIEW

This review provides readers with examples of refractory infections due to inborn errors of immunity, highlighting how they may be successfully treated by deducing and targeting the underlying immunodeficiency.

RECENT FINDINGS

The use of host-directed immunotherapy to treat infectious disease in inborn errors of immunity is currently limited but growing. Different strategies include depleting the cellular reservoir for pathogens with restricted cell-tropism; augmenting the diminished effector response; and restoring molecular equipoise. The immunotherapies illustrated are existing drugs that have been re-purposed and rationally used, depending on the molecular or cellular impact of the mutation. As more biologic response modifiers and molecular targeted therapies are developed for other indications, they open the avenues for their use in inborn errors of immunity. Conversely, as more molecular pathways underlying defective immune responses and refractory infections are elucidated, they lend themselves to tractability with these emerging therapies.

SUMMARY

Infections that fail appropriate antimicrobial therapy are a harbinger of underlying inborn errors of immunity. Dissecting the mechanism by which the immune system fails provides opportunities to target the host response and make it succeed.

Fibrosing mediastinitis in a child with Mendelian susceptibility to mycobacterial disease possibly due to Bacillus Calmette-Guérin

Background

Mendelian susceptibility to mycobacterial disease (MSMD) is an uncommon disorder with increased susceptibility to less virulent mycobacteria including bacillus Calmette-Guérin (BCG). Fibrosing mediastinitis (FM) is also a rare condition defined by excessive fibrotic reactions in the mediastinum. So far, some infectious organisms and autoimmune diseases have been introduced as possible etiologies of FM. However, no study has ever discussed the possible association of BCG infection and FM.

Case presentation

In this study, we report a 3-year-old female presenting with persistent fever, weakness, and bloody diarrhea in addition to mediastinal lymphadenopathy, hepatosplenomegaly, and pleural and pericardial effusion. Further examinations established a diagnosis of MSMD based on her clinical condition, immunologic data, positive tests for mycobacterial species, positive family history, and genetic study (IL12RB1 gene, c.G1193C, p.W398S). A year and a half later, she was referred with submandibular lymphadenitis and underwent immunologic work-up which revealed high inflammatory indices, a slight reduction in numbers of CD3 + and CD4 + cells as well as elevated CD16/56 + cell count and hyperimmunoglobulinemia. Purified protein derivative (PPD), QuantiFERON, and gastric washing test were all negative. Her chest computed tomography (CT) scan revealed suspicious para-aortic soft tissue and her echocardiography was indicative of strictures in superior vena cava and pulmonary veins. She further underwent chest CT angiography which confirmed FM development. Meanwhile, she has been treated with anti-mycobacterial agents and subcutaneous IFN-γ.

Conclusion

In summary, we described a novel case of MSMD in a child presenting with granulomatous FM possibly following BCG infection. This is the first report introducing aberrant BCG infection as the underlying cause of FM. This result could assist physicians in identifying early-onset FM in suspicious cases with MSMD. However, more studies are required to support this matter.

A novel STAT1 loss-of-function mutation associated with Mendelian susceptibility to mycobacterial disease

Mendelian susceptibility to mycobacterial diseases (MSMD) is a rare congenital immune deficiency characterized by susceptibility to weakly virulent mycobacteria. Loss-of-function (LOF) mutation of signal transducer and activator of transcription 1 (STAT1) is one of the common genetic causes of MSMD. In this study, we identified a patient who presented with multiple lymph node enlargements and multiple osteolytic disruptions. Mycobacterium gordonae infection was confirmed by metagenomic next-generation sequencing. Whole-exome sequencing identified a novel paternal heterozygous mutation in exon 22 of STAT1 (NM_007315.4, c.1892T>C, p.Val631Ala). This variant was confirmed pathogenic by multiple software predictions. Based on functional assays, STAT1 expression in STAT1^V631A cells was not different from STAT1^WT cells. But STAT1^V631A mutation caused much lower activation of STAT1 when stimulated by interferon-γ (IFN-γ). Fluorescence localization analysis revealed that both STAT1^V631A and STAT1^WT proteins were located in the cytoplasm, and only a few STAT1^V631A proteins were translocated to the nucleus in response to IFN-γ. These results suggest that STAT1^V631A leads to LOF in IFN-γ-mediated mycobacterial immunity, resulting in MSMD. Treatment with antibiotics has achieved ideal disease control for this patient, and no adverse events occurred during follow-up. The STAT1 LOF deficiency is a genetic cause of MSMD, which should be considered in patients with mycobacterial disease, especially those with bone involvement.

Candidate genes and sequence variants for susceptibility to mycobacterial infection identified by whole-exome sequencing

Inborn errors of immunity are known to influence susceptibility to mycobacterial infections. The aim of this study was to characterize the genetic profile of nine patients with mycobacterial infections (eight with BCGitis and one with disseminated tuberculosis) from the Republic of Moldova using whole-exome sequencing. In total, 12 variants in eight genes known to be associated with Mendelian Susceptibility to Mycobacterial Disease (MSMD) were detected in six out of nine patients examined. In particular, a novel splice site mutation c.373–2A>C in STAT1 gene was found and functionally confirmed in a patient with disseminated tuberculosis. Trio analysis was possible for seven out of nine patients, and resulted in 23 candidate variants in 15 novel genes. Four of these genes - GBP2, HEATR3, PPP1R9B and KDM6A were further prioritized, considering their elevated expression in immune-related tissues. Compound heterozygosity was found in GBP2 in a single patient, comprising a maternally inherited missense variant c.412G>A/p.(Ala138Thr) predicted to be deleterious and a paternally inherited intronic mutation c.1149+14T>C. Functional studies demonstrated that the intronic mutation affects splicing and the level of transcript. Finally, we analyzed pathogenicity of variant combinations in gene pairs and identified five patients with putative oligogenic inheritance. In summary, our study expands the spectrum of genetic variation contributing to susceptibility to mycobacterial infections in children and provides insight into the complex/oligogenic disease-causing mode.

Occurrence of extrapulmonary tuberculosis is associated with geographical origin: spatial characteristics of the Frankfurt TB cohort 2013-2018

INTRODUCTION

Tuberculosis (TB) is caused by M. tuberculosis complex (MTB) and pulmonary tuberculosis (PTB) is its classical manifestation. However, in some regions of the world, extrapulmonary TB (EPTB) seems to be more frequent.

METHODS

We performed a retrospective cohort study of all TB patients treated at University Hospital Frankfurt, Germany, for the time period 2013-2018. Patient charts were reviewed and demographic, clinical, and microbiological data recorded. Patients were subdivided according to their geographic origins.

RESULTS

Of the 378 included patients, 309 were born outside Germany (81.7%). Three WHO regions were significantly associated with the occurrence of isolated EPTB: the South-East Asian Region (OR 3.37, CI 1.74-6.66, p < 0.001), the African Region (2.20, CI 1.25-3.90, p = 0.006), and the Eastern Mediterranean Region (OR 3.18, CI 1.78-5.76, p < 0.001). On a country level, seven countries of origin could be demonstrated to be significantly associated with the occurrence of isolated EPTB: India (OR 5.58, CI 2.30-14.20, p < 0.001), Nepal (OR 12.75, CI 1.73-259.28, p = 0.027), Afghanistan (OR 3.64, CI 1.14-11.98, p = 0.029), Pakistan (OR 3.64, CI 1.14-11.98, p = 0.029), Eritrea (OR 3.32, CI 1.52-7.47, p = 0.003), Somalia (OR 7.08, CI 2.77-19.43, p < 0.001), and Turkey (OR 9.56, CI 2.52-47.19, p = 0.002).

CONCLUSION

Geographical origin is a predictor for the occurrence of extrapulmonary TB. This might be linked to a delay in diagnosis in these patients, as well as specific responsible impairments of the host's immune system, possible virulence factors of MTB, and relevant comorbidities.

Role of Interferons in Mycobacterium tuberculosis Infection

Considerable measures have been implemented in healthcare institutions to screen for and treat tuberculosis (TB) in developed countries; however, in low- and middle-income countries, many individuals still suffer from TB’s deleterious effects. TB is caused by an infection from the Mycobacterium tuberculosis (M. tb) bacteria. Symptoms of TB may range from an asymptomatic latent-phase affecting the pulmonary tract to a devastating active and disseminated stage that can cause central nervous system demise, musculoskeletal impairments, and genitourinary compromise. Following M. tb infection, cytokines such as interferons (IFNs) are released as part of the host immune response. Three main classes of IFNs prevalent during the immune defense include: type I IFN (α and β), type II IFN (IFN-γ), and type III IFN (IFN-λ). The current literature reports that type I IFN plays a role in diminishing the host defense against M. tb by attenuating T-cell activation. In opposition, T-cell activation drives type II IFN release, which is the primary cytokine mediating protection from M. tb by stimulating macrophages and their oxidative defense mechanisms. Type III IFN has a subsidiary part in improving the Th1 response for host cell protection against M. tb. Based on the current evidence available, our group aims to summarize the role that each IFN serves in TB within this literature review.

Manifestations of cutaneous mycobacterial infections in patients with inborn errors of IL-12/IL-23-IFNγ immunity

Background

Inborn errors of IL-12/IL-23-IFNγ immunity underlie Mendelian susceptibility to mycobacterial diseases (MSMD), a group of immunodeficiencies characterized by a highly selective susceptibility to weakly virulent strains of mycobacteria, such as non-tuberculous mycobacteria (NTM) and bacillus Calmette-Guérin (BCG). Cutaneous mycobacterial infections are common in MSMD and may represent a red flag for this immunodeficiency.

Objectives

We present a case series of four paediatric patients with MSMD, specifically with IFNγR1 and STAT1 deficiencies, and cutaneous NTM/BCG infections to increase awareness of this immunodeficiency, which may, in some cases, be intercepted by the dermatologist and thus timely referred to the immunologist.

Materials & Methods

Clinical, laboratory and genetic investigations of the four paediatric patients with MSMD are presented.

Results

All four presented patients experienced early complications after BCG vaccination. Two patients suffered recurrent mycobacteriosis, one patient experienced delayed BCG reactivation, and one patient died of disseminated avian mycobacteriosis. The dermatological manifestation in these patients included destructive nasal ulcerations, scrofuloderma of various sites and lupus vulgaris. All patients had a normal basic immune phenotype.

Conclusion

The presented cases demonstrate that NTM/BCG infections in otherwise seemingly immunocompetent patients should raise suspicion of MSMD. This is of utmost importance as specific therapeutic approaches, such as IFNγ treatment or haematopoietic stem cell transplantation, may be employed to improve the disease outcome.

IL12RB1 allele bias in human TH cells is regulated by functional SNPs in its 3'UTR

Allele bias is an epigenetic mechanism wherein only the maternal- or paternal-derived allele of a gene is preferentially expressed. Allele bias is used by T cells to regulate expression of numerous genes, including those which govern their development and response to cytokines. Here we demonstrate that human T_H cell expression of the cytokine receptor gene IL12RB1 is subject to allele bias, and the extent to which this bias occurs is influenced by cells' differentiation status and two polymorphic sites in the IL12RB1 3'UTR. The single nucleotide polymorphisms (SNPs) at these sites, rs3746190 and rs404733, function to increase expression of their encoding allele. Modeling suggests this is due to a stabilizing effect of these SNPs on the predicted mRNA secondary structure. The SNP rs3746190 is also proximal to the predicted binding site of microRNA miR-1277, raising the possibility that miR-1277 cannot exert suppression in the presence of rs3746190. Functional experiments demonstrate, however, that miR-1277 suppression of IL12RB1 3'UTR expression-which itself has not been previously reported-is nevertheless independent of rs3746190. Collectively, these data demonstrate that rs3746190 and rs404733 are functional SNPs which regulate IL12RB1 allele bias in human T_H cells.

Human Pulmonary Tuberculosis: Understanding the Immune Response in the Bronchoalveolar System

Mycobacterium tuberculosis, the causal agent of one of the most devastating infectious diseases worldwide, can evade or modulate the host immune response and remain dormant for many years. In this review, we focus on identifying the local immune response induced in vivo by M. tuberculosis in the lungs of patients with active tuberculosis by analyzing data from untouched cells from bronchoalveolar lavage fluid (BALF) or exhaled breath condensate (EBC) samples. The most abundant resident cells in patients with active tuberculosis are macrophages and lymphocytes, which facilitate the recruitment of neutrophils. The cellular response is characterized by an inflammatory state and oxidative stress produced mainly by macrophages and T lymphocytes. In the alveolar microenvironment, the levels of cytokines such as interleukins (IL), chemokines, and matrix metalloproteinases (MMP) are increased compared with healthy patients. The production of cytokines such as interferon (IFN)-γ and IL-17 and specific immunoglobulin (Ig) A and G against M. tuberculosis indicate that the adaptive immune response is induced despite the presence of a chronic infection. The role of epithelial cells, the processing and presentation of antigens by macrophages and dendritic cells, as well as the role of tissue-resident memory T cells (Trm) for in situ vaccination remains to be understood.

From rare disorders of immunity to common determinants of infection: Following the mechanistic thread

The immense interindividual clinical variability during any infection is a long-standing enigma. Inborn errors of IFN-γ and IFN-α/β immunity underlying rare infections with weakly virulent mycobacteria and seasonal influenza virus have inspired studies of two common infections: tuberculosis and COVID-19. A TYK2 genotype impairing IFN-γ production accounts for about 1% of tuberculosis cases, and autoantibodies neutralizing IFN-α/β account for about 15% of critical COVID-19 cases. The discovery of inborn errors and mechanisms underlying rare infections drove the identification of common monogenic or autoimmune determinants of related common infections. This "rare-to-common" genetic and mechanistic approach to infectious diseases may be of heuristic value.

Sex Differences in Active Pulmonary Tuberculosis Outcomes in Mali, West Africa

Men and women often respond differently to infectious diseases and their treatments. Tuberculosis (TB) is a life-threatening communicable disease that affects more men than women globally. Whether male sex is an independent risk factor for unfavorable TB outcomes, however, has not been rigorously investigated in an African context, where individuals are likely exposed to different microbial and environmental factors. We analyzed data collected from a cohort study in Mali by focusing on newly diagnosed active pulmonary TB individuals who were treatment naive. We gathered baseline demographic, clinical, and microbiologic characteristics before treatment initiation and also at three time points during treatment. More males than females were affected with TB, as evidenced by a male-to-female ratio of 2.4:1. In addition, at baseline, males had a significantly higher bacterial count and shorter time to culture positivity as compared with females. Male sex was associated with lower smear negativity rate after 2 months of treatment also known as the intensive phase of treatment, but not at later time points. There was no relationship between patients' sex and mortality from any cause during treatment. This study suggests that sex-based differences in TB outcomes exist, with sex-specific effects on disease outcomes being more pronounced before treatment initiation and during the intensive phase of treatment rather than at later phases of treatment.

Chronic Granulomatous Disease-Like Presentation of a Child with Autosomal Recessive PKCδ Deficiency

BACKGROUND

Autosomal recessive (AR) PKCδ deficiency is a rare inborn error of immunity (IEI) characterized by autoimmunity and susceptibility to bacterial, fungal, and viral infections. PKCδ is involved in the intracellular production of reactive oxidative species (ROS).

MATERIAL AND METHODS

We studied a 5-year old girl presenting with a history of Burkholderia cepacia infection. She had no history of autoimmunity, lymphocyte counts were normal, and no auto-antibodies were detected in her plasma. We performed a targeted panel analysis of 407 immunity-related genes and immunological investigations of the underlying genetic condition in this patient.

RESULTS

Consistent with a history suggestive of chronic granulomatous disease (CGD), oxidative burst impairment was observed in the patient's circulating phagocytes in a dihydrorhodamine 123 (DHR) assay. However, targeted genetic panel analysis identified no candidate variants of known CGD-causing genes. Two heterozygous candidate variants were detected in PRKCD: c.285C > A (p.C95*) and c.376G > T (p.D126Y). The missense variant was also predicted to cause abnormal splicing, as it is located at the splice donor site of exon 5. TOPO-TA cloning confirmed that exon 5 was completely skipped, resulting in a truncated protein. No PKCδ protein was detected in the patient's neutrophils and monocyte-derived macrophages. The monocyte-derived macrophages of the patient produced abnormally low levels of ROS, as shown in an Amplex Red assay.

CONCLUSION

PKCδ deficiency should be considered in young patients with CGD-like clinical manifestations and abnormal DHR assay results, even in the absence of clinical and biological manifestations of autoimmunity.

Defects of the Innate Immune System and Related Immune Deficiencies

The innate immune system is the host's first line of defense against pathogens. Toll-like receptors (TLRs) are pattern recognition receptors that mediate recognition of pathogen-associated molecular patterns. TLRs also activate signaling transduction pathways involved in host defense, inflammation, development, and the production of inflammatory cytokines. Innate immunodeficiencies associated with defective TLR signaling include mutations in NEMO, IKBA, MyD88, and IRAK4. Other innate immune defects have been associated with susceptibility to herpes simplex encephalitis, viral infections, and mycobacterial disease, as well as chronic mucocutaneous candidiasis and epidermodysplasia verruciformis. Phagocytes and natural killer cells are essential members of the innate immune system and defects in number and/or function of these cells can lead to recurrent infections. Complement is another important part of the innate immune system. Complement deficiencies can lead to increased susceptibility to infections, autoimmunity, or impaired immune complex clearance. The innate immune system must work to quickly recognize and eliminate pathogens as well as coordinate an immune response and engage the adaptive immune system. Defects of the innate immune system can lead to failure to quickly identify pathogens and activate the immune response, resulting in susceptibility to severe or recurrent infections.

An Updated Review on MSMD Research Globally and A Literature Review on the Molecular Findings, Clinical Manifestations, and Treatment Approaches in China

Mendelian susceptibility to mycobacterial disease (MSMD) arises from a group of rare inherited errors of immunity that result in selective susceptibility of otherwise healthy people to clinical disease caused by low virulence strains of mycobacteria, such as Mycobacterium bovis Bacille Calmette-Guérin (BCG) and environmental mycobacteria. Patients have normal resistance to other pathogens and no overt abnormalities in routine immunological and hematological evaluations for primary immunodeficiencies. At least 19 genes and 34 clinical phenotypes have been identified in MSMD. However, there have been no systematic reports on the clinical characteristics and genetic backgrounds of MSMD in China. In this review, on the one hand, we summarize an update findings on molecular defects and immunological mechanisms in the field of MSMD research globally. On the other hand, we undertook a systematic review of PubMed (MEDLINE), the Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, EMBASE, CNKI, and Wanfang to identify articles published before Jan 23, 2022, to summarize the clinical characteristics, diagnosis, treatment, and prognosis of MSMD in China. All the English and Chinese publications were searched without any restriction on article types.

Pathogenic autoantibodies to IFN-γ act through the impedance of receptor assembly and Fc-mediated response

Anti-interferon (IFN)-γ autoantibodies (AIGAs) are a pathogenic factor in late-onset immunodeficiency with disseminated mycobacterial and other opportunistic infections. AIGAs block IFN-γ function, but their effects on IFN-γ signaling are unknown. Using a single-cell capture method, we isolated 19 IFN-γ-reactive monoclonal antibodies (mAbs) from patients with AIGAs. All displayed high-affinity (KD < 10-9 M) binding to IFN-γ, but only eight neutralized IFN-γ-STAT1 signaling and HLA-DR expression. Signal blockade and binding affinity were correlated and attributed to somatic hypermutations. Cross-competition assays identified three nonoverlapping binding sites (I-III) for AIGAs on IFN-γ. We found that site I mAb neutralized IFN-γ by blocking its binding to IFN-γR1. Site II and III mAbs bound the receptor-bound IFN-γ on the cell surface, abolishing IFN-γR1-IFN-γR2 heterodimerization and preventing downstream signaling. Site III mAbs mediated antibody-dependent cellular cytotoxicity, probably through antibody-IFN-γ complexes on cells. Pathogenic AIGAs underlie mycobacterial infections by the dual blockade of IFN-γ signaling and by eliminating IFN-γ-responsive cells.

A Novel Homozygous Stop Mutation in IL23R Causes Mendelian Susceptibility to Mycobacterial Disease

PURPOSE

Mendelian susceptibility to mycobacterial disease (MSMD) is caused by inborn errors of IFN-γ immunity. The most frequent genetic defects are found in IL12 or a subunit of its receptor. IL23R deficiency in MSMD has only been reported once, in two pediatric patients from the same kindred with isolated disseminated Bacille Calmette-Guérin disease. We evaluated the impact of a homozygous stop mutation in IL23R (R381X), identified by whole exome sequencing, in an adult patient with disseminated non-tuberculous mycobacterial disease.

METHODS

We performed functional validation of the R381X mutation by evaluating IL23R expression and IL-23 signaling (STAT3 phosphorylation, IFN-γ production) in primary cells (PBMCs, EBV-B cells) and cell lines (HeLa) with or without back-complementation of wild-type IL23R.

RESULTS

We report on a 48-year-old male with disseminated non-tuberculous mycobacterial disease. We identified and characterized a homozygous loss-of-function stop mutation underlying IL23R deficiency, resulting in near absent expression of membrane bound IL23R. IL23R deficiency was characterized by impaired IL-23-mediated IFN-γ secretion in CD4⁺, CD8⁺ T, and mucosal-associated invariant T (MAIT) cells, and low frequencies of circulating Th17 (CD3⁺CD45RA^-CCR4⁺CXCR3^-RORγT⁺), Th1* (CD45RA^-CCR4^-CXCR3⁺RORγT⁺), and MAIT (CD3⁺CD8⁺Vα7.2⁺CD161⁺) cells. Although the patient did not have a history of recurrent fungal infections, impaired Th17 differentiation and blunted IL-23-mediated IL-17 secretion in PBMCs were observed.

CONCLUSION

We demonstrate that impaired IL-23 immunity caused by a homozygous R381X mutation in IL23R underlies MSMD, corroborating earlier findings with a homozygous p.C115Y IL23R mutation. Our report further supports a model of redundant contribution of IL-23- to IL-17-mediated anti-fungal immunity.1.

Anti-cytokine autoantibodies and inborn errors of immunity

The past quarter of a century has witnessed an inordinate increase in our understanding of primary immunodeficiencies / inborn errors of immunity. These include a significant increase in the number of identified conditions, broadening the phenotypes of existing entities, delineation of classical inborn errors of immunity from those with a narrow phenotype, and a gradual shift from supportive to definitive care in patients afflicted with these diseases. It has also seen the discovery of conditions broadly defined as phenocopies of primary immunodeficiencies, where somatic mutations or autoantibodies mimic a recognised primary immunodeficiency's presentation in the absence of the underlying genetic basis for that disease. This article will provide a review of the anti-cytokine autoantibody-mediated phenocopies of inborn errors of immunity and discuss the therapeutic and laboratory aspects of this group of diseases.

BCG Infection in Patients With Inborn Errors of Immunity Receiving the Russian BCG Strain

BACKGROUND

Bacillus Calmette-Guierin (BCG) vaccination complications are common in inborn errors of immunity (IEI) due to the inability to clear live attenuated Mycobacterium bovis. Various BCG-vaccine strains are used worldwide, and the profile of the Russian BCG strain vaccine complications in IEI is poorly characterized.

OBJECTIVE

To evaluate risks of BCG infection in a large cohort of patients with IEI vaccinated with the Russian BCG strain.

METHODS

We evaluated 778 patients with IEI vaccinated with the Russian BCG strain.

RESULTS

A total of 114 (15%) developed BCG infection, 41 (36%) with local, 19 (17%) with regional, and 54 with (47%) disseminated disease. BCG infection was seen in 58% of the patients with severe combined immunodeficiency (SCID), 82% with chronic granulomatous disease, 50% with innate immune defects, 5% with combined immunodeficiency, and 2% with other IEI. BCG infection presented at a median age of 4 to 5 months in SCID, chronic granulomatous disease, combined immunodeficiency, and other IEI groups versus 12 months in patients with innate immune defects (P < .005). We found no influence of specific genetic defects, CD3⁺ and natural killer cell numbers in SCID, or dihydrorhodamine test stimulation index values in chronic granulomatous disease on the BCG-infection risks. All patients with SCID received antimycobacterial therapy at SCID diagnosis even in the absence of active BCG infection. More antimycobacterial agents were required in disseminated relative to local or regional infection (P < .0001). Only 1 of 114 patients (with SCID) died of BCG-related complications (<1%).

CONCLUSIONS

BCG infection is common in patients with IEI receiving BCG vaccination. Rational early antimycobacterial therapy, combined with anticytokine agents for posttransplant inflammatory syndrome prevention, and treatment in SCID may prevent BCG-related mortality.

The Pathogenesis of Giant Condyloma Acuminatum (Buschke-Lowenstein Tumor): An Overview

Giant condyloma acuminatum, also known as Buschke-Lowenstein tumor (BLT), is a rare disease of the anogenital region. BLT is considered a locally aggressive tumor of benign histological appearance, but with the potential for destructive growth and high recurrence rates. BLT development is strongly associated with infection with low-risk human papillomaviruses (HPVs), mostly HPV-6 and -11. Immunity to HPVs plays a crucial role in the natural control of various HPV-induced lesions. Large condyloma acuminata are frequently reported in patients with primary (e.g., DOCK8 or SPINK5 deficiencies) and secondary (e.g., AIDS, solid organ transplantation) immune defects. Individuals with extensive anogenital warts, including BLT in particular, should therefore be tested for inherited or acquired immunodeficiency. Research into the genetic basis of unexplained cases is warranted. An understanding of the etiology of BLT would lead to improvements in its management. This review focuses on the role of underlying HPV infections, and human genetic and immunological determinants of BLT.

Human autoantibodies underlying infectious diseases

The vast interindividual clinical variability observed in any microbial infection-ranging from silent infection to lethal disease-is increasingly being explained by human genetic and immunological determinants. Autoantibodies neutralizing specific cytokines underlie the same infectious diseases as inborn errors of the corresponding cytokine or response pathway. Autoantibodies against type I IFNs underlie COVID-19 pneumonia and adverse reactions to the live attenuated yellow fever virus vaccine. Autoantibodies against type II IFN underlie severe disease caused by environmental or tuberculous mycobacteria, and other intra-macrophagic microbes. Autoantibodies against IL-17A/F and IL-6 are less common and underlie mucocutaneous candidiasis and staphylococcal diseases, respectively. Inborn errors of and autoantibodies against GM-CSF underlie pulmonary alveolar proteinosis; associated infections are less well characterized. In individual patients, autoantibodies against cytokines preexist infection with the pathogen concerned and underlie the infectious disease. Human antibody-driven autoimmunity can interfere with cytokines that are essential for protective immunity to specific infectious agents but that are otherwise redundant, thereby underlying specific infectious diseases.

Respiratory Infections in Patients with Primary Immunodeficiency

Recurrent and life-threatening respiratory infections are nearly universal in patients with primary immunodeficiency diseases (PIDD). Early recognition, aggressive treatment, and prophylaxis with antimicrobials and immunoglobulin replacement have been the mainstays of management and will be reviewed here with an emphasis on respiratory infections. Genetic discoveries have allowed direct translation of research to clinical practice, improving our understanding of clinical patterns of pathogen susceptibilities and guiding prophylaxis. The recent identification of inborn errors in type I interferon signaling as a basis for life-threatening viral infections in otherwise healthy individuals suggests another targetable pathway for treatment and/or prophylaxis. The future of PIDD diagnosis will certainly involve early genetic identification by newborn screening before onset of infections, with early treatment offering the potential of preventing disease complications such as chronic lung changes. Gene editing approaches offer tremendous therapeutic potential, with rapidly emerging delivery systems. Antiviral therapies are desperately needed, and specific cellular therapies show promise in patients requiring hematopoietic stem cell transplantation. The introduction of approved therapies for clinical use in PIDD is limited by the difficulty of studying outcomes in rare patients/conditions with conventional clinical trials.

Effective anti-mycobacterial treatment for BCG disease in patients with Mendelian Susceptibility to Mycobacterial Disease (MSMD): a case series

Background

Post-vaccination BCG disease typically attests to underlying inborn errors of immunity (IEIs), with the highest rates of complications in patients with Mendelian susceptibility to mycobacterial disease (MSMD). However, therapeutic protocols for the management of BCG-osis (disseminated) and persistent BCG-itis (localized) are still controversial.

Methods

Twenty-four Iranian patients with MSMD (BCG-osis or BCG-itis), followed from 2009 to 2020 in Tehran, were included in the study. Their medical records were retrospectively reviewed for demographics, clinical features, laboratory findings, and molecular diagnosis. The therapeutic protocol sheets were prepared to contain the types and duration of anti-mycobacterial agents.

Results

BCG disease either as BCG-itis (33.3%) or BCG-osis (66.7%) was confirmed in all patients by positive gastric washing test (54.2%), microbial smear and culture (58.3%), or purified protein derivative (PPD) test (4.2%). The duration between BCG-osis onset and MSMD diagnosis was 21.6 months.

All except three patients were initiated on second-line anti-mycobacterial agents with either a fluoroquinolone (levofloxacin: 15 mg/kg/day, ciprofloxacin: 20 mg/kg/day, ofloxacin: 15 mg/kg/day), aminoglycoside (amikacin: 10–15 mg/kg/day, streptomycin: 15 mg/kg/day), and/or macrolide (clarithromycin: 15 mg/kg/day) along with oral rifampin (10 mg/kg/day), isoniazid (15 mg/kg/day), and ethambutol (20 mg/kg/day). Three patients showed a clinical response to rifampin, despite in vitro resistance. Fourteen (58.3%) patients received also adjuvant subcutaneous IFN-γ therapy, 50 µ/m² every other day. At the end of survey, most patients (n = 22, 91.7%) were alive and two patients died following BCG-osis and respiratory failure.

Conclusions

We recommend the early instigation of second-line anti-mycobacterial agents in MSMD patients with BCG disease.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12941-022-00500-y.

Epigenetic Alterations in Inborn Errors of Immunity

The epigenome bridges environmental factors and the genome, fine-tuning the process of gene transcription. Physiological programs, including the development, maturation and maintenance of cellular identity and function, are modulated by intricate epigenetic changes that encompass DNA methylation, chromatin remodeling, histone modifications and RNA processing. The collection of genome-wide DNA methylation data has recently shed new light into the potential contribution of epigenetics in pathophysiology, particularly in the field of immune system and host defense. The study of patients carrying mutations in genes encoding for molecules involved in the epigenetic machinery has allowed the identification and better characterization of environment-genome interactions via epigenetics as well as paving the way for the development of new potential therapeutic options. In this review, we summarize current knowledge of the role of epigenetic modifications in the immune system and outline their potential involvement in the pathogenesis of inborn errors of immunity.

Unbalanced serum immunoglobulins in clinical subtypes of pediatric tuberculosis disease

Immune response to tuberculosis (TB) has been extensively studied in the past decades and classically involves cellular immunity. However, evidence suggests that humoral immunity may play a relevant role. Past studies regarding serum immunoglobulin (Ig) levels in TB are dated and only involve adult subjects. In this study, we retrospectively studied a cohort of 256 children with TB disease and analyzed 111 patients screened for total serum Ig at diagnosis. According to the severity and extent of organ involvement, subjects were divided into four groups, namely, uncomplicated pulmonary TB (UCPTB, 56.3% of patients), complicated pulmonary TB (CPTB, 22.5%), lymph node extrapulmonary TB (LN-EPTB, 7.2%), and extra-nodal extrapulmonary TB (EN-EPTB, 13.5%). Serum IgG and IgA levels were significantly higher in more severe and extended TB disease. Median IgG levels progressively increased from uncomplicated to complicated pulmonary and nodal forms, reaching their highest values in diffuse extra-pulmonary TB. In parallel, UCPTB showed significantly lower frequencies of patients presenting a substantial increase in IgG levels when compared with the other three groups. No relevant differences in IgM levels were detected. Ig screening at follow-up showed a significant reduction in IgG and IgA levels. Finally, we unveiled three cases of selective IgA and one case of selective IgM deficiencies (SIgMD), the latter with a severe clinical course. Serum IgG and IgA may be a useful clinical tool to assess the severity and monitor the treatment response in pediatric TB disease. Moreover, immunological workup in children with TB disease may unmask primary defects of humoral immunity.

Case Report: Disseminated Mycobacterium intracellulare Infection With More Than 1-Year Follow-Up in a Young Boy With IFNGR1 Deficiency

All members of the genus Mycobacterium are collectively labeled as "non-tuberculous mycobacterium" (NTM), with the exception of the Mycobacterium tuberculosis complex and M. leprae. Recently, the incidence of NTM infection and number of cases have been increasing, but their identification remains difficult in some countries. Usually, NTM infections and diseases are associated with primary immunodeficiency diseases (PIDs), and their prognoses can be improved with a timely diagnosis and appropriate treatment. Here, we report a case of a 3-year-old boy with disseminated NTM disease (Mycobacterium intracellulare) and interferon-γ receptor 1 (IFNGR1) deficiency. He presented with skin and soft-tissue disease, disseminated osteomyelitis, and pulmonary disease. Initially, we suspected an infection due to the Bacillus Calmette-Guérin vaccine but later suspected Langerhans cell histiocytosis. Following oral treatment of azithromycin, rifampicin, and ethambutol, his condition improved progressively according to clinical and imaging manifestations. This case highlights the importance of early identification of the pathogen in a timely prescription of specific treatments in PIDs patients. We also discuss our experience of treatment of M. intracellulare disease in patients with IFNGR1 deficiency.

High overall mortality of Mycobacterium genavense infections and impact of antimycobacterial therapy: Systematic review and individual patient data meta-analysis

INTRODUCTION

Mycobacterium genavense is a fastidious slow growing mycobacterium (SGM) that causes disseminated infections in immunocompromised hosts. It has been described in HIV-positive individuals and increasingly in patients without HIV. The infections are difficult to treat and the optimal antimycobacterial regimen is still unknown.

METHODS

An individual patient data meta-analysis was conducted aiming at including all hitherto published cases of infection with M. genavense. Clinical manifestations, microbiological data, dispositions and immunosuppression were recorded. Antimycobacterial therapies and mortality were analyzed by logistic regression and time-to-event analysis.

RESULTS

We included 223 patients with infection due to M. genavense published from 1992 to 2021. While the majority was HIV positive (n = 171, 76.7%), 52 patients were non-HIV-patients (23.3%), 36 of whom received immunosuppressive therapy (69%). We could confirm the bacterium's tropism for the gastrointestinal tract with abdominal pain, hepato-/splenomegaly and abdominal lymphadenopathy being major clinical manifestations. More than 90% of patients received antimycobacterial therapy. The regimens consisted mainly of macrolides, rifamycins and ethambutol. Overall mortality was high, but in logistic regression and time-to-event analysis a macrolide containing regimen was associated with better outcomes.

CONCLUSION

In this first individual patient data meta-analysis of infections with M. genavense we confirm its tropism for the gastrointestinal tract. The high overall mortality underlines the clinical relevance of infection with this bacterium for the individual patient. In addition, our data give a hint that a macrolide containing regimen is associated with better survival.

A Critical Review on the Standardization and Quality Assessment of Nonfunctional Laboratory Tests Frequently Used to Identify Inborn Errors of Immunity

Inborn errors of immunity (IEI), which were previously termed primary immunodeficiency diseases, represent a large and growing heterogeneous group of diseases that are mostly monogenic. In addition to increased susceptibility to infections, other clinical phenotypes have recently been associated with IEI, such as autoimmune disorders, severe allergies, autoinflammatory disorders, benign lymphoproliferative diseases, and malignant manifestations. The IUIS 2019 classification comprises 430 distinct defects that, although rare individually, represent a group affecting a significant number of patients, with an overall prevalence of 1:1,200-2,000 in the general population. Early IEI diagnosis is critical for appropriate therapy and genetic counseling, however, this process is deeply dependent on accurate laboratory tests. Despite the striking importance of laboratory data for clinical immunologists, several IEI-relevant immunoassays still lack standardization, including standardized protocols, reference materials, and external quality assessment programs. Moreover, well-established reference values mostly remain to be determined, especially for early ages, when the most severe conditions manifest and diagnosis is critical for patient survival. In this article, we intend to approach the issue of standardization and quality control of the nonfunctional diagnostic tests used for IEI, focusing on those frequently utilized in clinical practice. Herein, we will focus on discussing the issues of nonfunctional immunoassays (flow cytometry, enzyme-linked immunosorbent assays, and turbidimetry/nephelometry, among others), as defined by the pure quantification of proteins or cell subsets without cell activation or cell culture-based methods.

Signal peptide peptidase-like 2 proteases: Regulatory switches or proteasome of the membrane?

Signal peptide peptidase-like 2 (SPPL) proteases constitute a subfamily of SPP/SPPL intramembrane proteases which are homologues of the presenilins, the catalytic core of the γ-secretase complex. The three SPPL2 proteases SPPL2a, SPPL2b and SPPL2c proteolyse single-span, type II-oriented transmembrane proteins and/or tail-anchored proteins within their hydrophobic transmembrane segments. We review recent progress in defining substrate spectra and in vivo functions of these proteases. Characterisation of the respective knockout mice has implicated SPPL2 proteases in immune cell differentiation and function, prevention of atherosclerotic plaque development and spermatogenesis. Mechanisms how substrates are selected by these enzymes are still incompletely understood. We will discuss current views on how selective SPPL2-mediated cleavage is or whether these proteases may exhibit a generalised role in the turnover of membrane proteins. This has been suggested previously for the mechanistically related γ-secretase for which the term "proteasome of the membrane" has been coined based on its broad substrate spectrum. With regard to individual substrates, potential signalling functions of the resulting cytosolic cleavage fragments remain a controversial aspect. However, it has been clearly shown that SPPL2 proteases can influence cellular signalling and membrane trafficking by controlling levels of their membrane-bound substrate proteins which highlights these enzymes as regulatory switches. Based on this, regulatory mechanisms controlling activity of SPPL2 proteases would need to be postulated, which are just beginning to emerge. These different questions, which are relevant for other families of intramembrane proteases in a similar way, will be critically discussed based on the current state of knowledge.

GATA2 deficiency phenotype associated with tandem duplication GATA2 and over-expression of GATA2-AS1

Typical features of GATA2 deficiency were associated with a de novo tandem duplication of GATA2 and increased expression of GATA2-AS1.

The duplication contained a maternally inherited deletion copy number polymorphism esv2725896/nsv513733.

A 3-year-old girl of nonconsanguineous healthy parents presented with cervical and mediastinal lymphadenopathy due to Mycobacterium fortuitum infection. Routine blood analysis showed normal hemoglobin, neutrophils, and platelets but profound mononuclear cell deficiency (monocytes < 0.1 × 10⁹/L; B cells 78/μL; NK cells 48/μL). A 548 902-bp region containing GATA2 was sequenced by targeted capture and deep sequencing. This revealed a de novo 187-kb duplication of the entire GATA2 locus, containing a maternally inherited copy number variation deletion of 25 kb (GRCh37: esv2725896 and nsv513733). Many GATA2-associated phenotypes have been attributed to amino acid substitution, frameshift/deletion, loss of intronic enhancer function, or aberrant splicing. Gene deletion has been described, but other structural variation has not been reported in the germline configuration. In this case, duplication of the GATA2 locus was paradoxically associated with skewed diminished expression of GATA2 messenger RNA and loss of GATA2 protein. Chimeric RNA fusion transcripts were not detected. A possible mechanism involves increased transcription of the anti-sense long noncoding RNA GATA2-AS1 (RP11-472.220), which was increased several fold. This case further highlights that evaluation of the allele count is essential in any case of suspected GATA2-related syndrome.

Human genetic and immunological dissection of papillomavirus-driven diseases: new insights into their pathogenesis

Human papillomaviruses (HPVs) are responsible for cutaneous and mucosal lesions. Persistent HPV infection remains a leading cause of uterine cancer in women, but also of cutaneous squamous cell carcinoma in patients with epidermodysplasia verruciformis (EV), and of rare and devastating benign tumors, such as 'tree-man' syndrome. HPV infections are usually asymptomatic or benign in the general population. Severe manifestations in otherwise healthy subjects can attest to inherited immunodeficiencies. The human genetic dissection of these cases has identified critical components of the immune response to HPVs, including the non-redundant roles of keratinocyte-intrinsic immunity in controlling β-HPVs, and of T cell-dependent adaptive immunity for controlling all HPV types. A key role of the CD28 T-cell costimulation pathway in controlling common warts due to HPVs was recently discovered. This review summarizes the state of the art in the human genetics of HPV infection, focusing on two key affected cell types: keratinocytes and T cells.

Herpes simplex encephalitis in a patient with a distinctive form of inherited IFNAR1 deficiency

Inborn errors of TLR3-dependent IFN-α/β- and IFN-λ-mediated immunity in the CNS can underlie herpes simplex virus 1 (HSV-1) encephalitis (HSE). The respective contributions of IFN-α/β and IFN-λ are unknown. We report a child homozygous for a genomic deletion of the entire coding sequence and part of the 3'-UTR of the last exon of IFNAR1, who died of HSE at the age of 2 years. An older cousin died following vaccination against measles, mumps, and rubella at 12 months of age, and another 17-year-old cousin homozygous for the same variant has had other, less severe, viral illnesses. The encoded IFNAR1 protein is expressed on the cell surface but is truncated and cannot interact with the tyrosine kinase TYK2. The patient's fibroblasts and EBV-B cells did not respond to IFN-α2b or IFN-β, in terms of STAT1, STAT2, and STAT3 phosphorylation or the genome-wide induction of IFN-stimulated genes. The patient's fibroblasts were susceptible to viruses, including HSV-1, even in the presence of exogenous IFN-α2b or IFN-β. HSE is therefore a consequence of inherited complete IFNAR1 deficiency. This viral disease occurred in natural conditions, unlike those previously reported in other patients with IFNAR1 or IFNAR2 deficiency. This experiment of nature indicates that IFN-α/β are essential for anti-HSV-1 immunity in the CNS.

Inherited human c-Rel deficiency disrupts myeloid and lymphoid immunity to multiple infectious agents

We studied a child with severe viral, bacterial, fungal, and parasitic diseases, who was homozygous for a loss-of-function mutation of REL, encoding c-Rel, which is selectively expressed in lymphoid and myeloid cells. The patient had low frequencies of NK, effector memory cells reexpressing CD45RA (Temra) CD8+ T cells, memory CD4+ T cells, including Th1 and Th1*, Tregs, and memory B cells, whereas the counts and proportions of other leukocyte subsets were normal. Functional deficits of myeloid cells included the abolition of IL-12 and IL-23 production by conventional DC1s (cDC1s) and monocytes, but not cDC2s. c-Rel was also required for induction of CD86 expression on, and thus antigen-presenting cell function of, cDCs. Functional deficits of lymphoid cells included reduced IL-2 production by naive T cells, correlating with low proliferation and survival rates and poor production of Th1, Th2, and Th17 cytokines by memory CD4+ T cells. In naive CD4+ T cells, c-Rel is dispensable for early IL2 induction but contributes to later phases of IL2 expression. The patient's naive B cells displayed impaired MYC and BCL2L1 induction, compromising B cell survival and proliferation and preventing their differentiation into Ig-secreting plasmablasts. Inherited c-Rel deficiency disrupts the development and function of multiple myeloid and lymphoid cells, compromising innate and adaptive immunity to multiple infectious agents.

Infection-induced inflammation from specific inborn errors of immunity to COVID-19

Inborn errors of immunity (IEIs) are a group of genetically defined disorders leading to defective immunity. Some IEIs have been linked to mutations of immune receptors or signaling molecules, resulting in defective signaling of respective cascades essential for combating specific pathogens. However, it remains incompletely understood why in selected IEIs, such as X-linked lymphoproliferative syndrome type 2 (XLP-2), hypo-immune response to specific pathogens results in persistent inflammation. Moreover, mechanisms underlying the generation of anticytokine autoantibodies are mostly unknown. Recently, IEIs have been associated with coronavirus disease 2019 (COVID-19), with a small proportion of patients that contract severe COVID-19 displaying loss-of-function mutations in genes associated with type I interferons (IFNs). Moreover, approximately 10% of patients with severe COVID-19 possess anti-type I IFN-neutralizing autoantibodies. Apart from IEIs that impair immune responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), SARS-CoV-2 encodes several proteins that suppress early type I IFN production. One primary consequence of the lack of type I IFNs during early SARS-CoV-2 infection is the increased inflammation associated with COVID-19. In XLP-2, resolution of inflammation rescued experimental subjects from infection-induced mortality. Recent studies also indicate that targeting inflammation could alleviate COVID-19. In this review, we discuss infection-induced inflammation in IEIs, using XLP-2 and COVID-19 as examples. We suggest that resolving inflammation may represent an effective therapeutic approach to these diseases.

Candidiasis in patients with APS-1: low IL-17, high IFN-γ, or both?

Chronic mucocutaneous candidiasis (CMC) is one of the earliest and most frequent clinical manifestations of autosomal recessive autoimmune polyendocrine syndrome type 1 (APS-1), a monogenic inborn error of immunity caused by deleterious variants of the autoimmune regulator (AIRE) gene. APS-1 patients suffer from various autoimmune diseases, due to the defective thymic deletion of autoreactive T cells, and the development of a large range of autoantibodies (auto-Abs) against various tissue antigens, and some cytokines. The mechanisms underlying CMC remained elusive for many years, until the description in 2010 of high serum titers of neutralizing auto-Abs against IL-17A, IL-17F, and/or IL-22, which are present in almost all APS-1 patients. Excessively high mucosal concentrations of IFN-γ were recently proposed as an alternative mechanism for CMC in APS-1.

Novel IL-β12R1 deficiency-mediates recurrent cutaneous leishmaniasis

BACKGROUND

The IL-12/IFN-γ axis plays a vital role in the control of intramacrophagic pathogens including Leishmania infections.

OBJECTIVE

The aim of this study was to investigate genetic defects in the IL-12/IFN-γ axis in cutaneous leishmaniasis patients, using immunological and genetic evaluation.

METHODS

Enzyme-linked immunosorbent assay was used to quantify IFN-γ , while flow cytometry was performed to analyze surface IL-12Rβ1/IL-12Rβ2 expression and phosphorylation of signal transducers as well as the activator of transcription 4 (pSTAT4). Sequencing was carried out for genetic analysis.

RESULTS

The peripheral blood mononuclear cells from the two patients (P1 and P2) demonstrated impaired production of IFN-γ. Furthermore, abolishment of the surface expression of Il-12Rβ1 was observed in lymphocytes, with consequent impairment of STAT4 phosphorylation in the lymphocytes of P1 and P2. IL-12Rββ1 deficiency was identified, which was caused by a novel homozygous missense mutation (c.485>T/p.P162L) and a novel homozygous nonsense mutation (c.805G>T/P.E269*) in the IL-12Rβ2 gene of P1 and P2, respectively. In silico analyses predicted these novel mutations as being pathogenic, causing truncated proteins, with consequent inactivation.

CONCLUSION

Our data have expanded the phenotype and mutation spectra associated with IL-12Rβ1 deficiency, and suggest that patients with CL should be screened for mutations in genes of the IL-12/IFN-γ axis.

Leukocytoclastic vasculitis in patients with IL12B or IL12RB1 deficiency: case report and review of the literature

BACKGROUND

Mendelian susceptibility to mycobacterial disease (MSMD) is an inborn error of immunity, resulting in susceptibility to weakly virulent mycobacteria and other intramacrophagic pathogens. Rheumatologic manifestations and vasculitis are considered rare manifestations in MSMD patients.

CASE PRESENTATION

In this study, we reported a 20-year-old female who was presented with recurrent lymphadenitis following bacillus Calmette-Guérin (BCG) vaccination and a history of recurrent disseminated rash diagnosed as leukocytoclastic vasculitis (LCV). A slight reduction in lymphocyte subsets including CD4+, CD19+, and CD 16 + 56 T-cell count, as well as an elevation in immunoglobulins level (IgG, IgA, IgM, IgE), were observed in the patient. Whole exome sequencing revealed a homozygous Indel-frameshift mutation, c.527_528delCT (p. S176Cfs*12), at the exon 5 of the IL12B gene. She experienced symptom resolution after treatment with anti-mycobacterial agents and subcutaneous IFN-γ. We conducted a manual literature search for MSMD patients reported with vasculitis in PubMed, Web of Science, and Scopus databases. A total of 18 MSMD patients were found to be affected by a variety of vasculitis phenotypes mainly including LCV and Henoch-Schönlein purpura (HSP) with often skin involvement. Patients were all involved with vasculitis at the median age of 6.8 (2.6-7.7) years, nearly 6.1 years after the initial presentations. Sixteen patients (88.9%) had IL12RB1 defects and concurrent Salmonella infection was reported in 15 (88.2%) patients.

CONCLUSION

The lack of IL-12 and IL-23 signaling/activity/function and salmonella infection may be triggering factors for the development of leukocytoclastic vasculitis. IL12B or IL12RB1 deficiency and salmonellosis should be considered in MSMD patients with vasculitis.

Outcome of Hematopoietic Stem Cell Transplantation in patients with Mendelian Susceptibility to Mycobacterial Diseases

Predisposition to mycobacterial infection is a key presenting feature of several rare inborn errors of intrinsic and innate immunity. Hematopoietic stem cell transplantation (HSCT) can be curative for such conditions, but published reports are few. We present a retrospective survey of the outcome of 11 affected patients (7 males, 4 females) who underwent HSCT between 2007 and 2019. Eight patients had disseminated mycobacterial infection prior to transplant. Median age at first transplant was 48 months (9 -192); three patients were successfully re-transplanted due to secondary graft failure. Donors were matched family (1), matched unrelated (3), and mismatched unrelated and haploidentical family (5 each). Stem cell source was peripheral blood (9), bone marrow (4), and cord blood (1). TCRαβ/CD19 + depletion was performed in 6. Conditioning regimens were treosulfan, fludarabine (4), with additional thiotepa (in 8), and fludarabine, melphalan (2); all had serotherapy with alemtuzumab (8) or anti T-lymphocyte globulin (6). Median hospital stay was 113 days (36–330). Three patients developed acute grade I-II skin and one grade IV skin graft versus host disease. Four patients had immune-reconstitution syndrome. Two reactivated cytomegalovirus (CMV), 1 Epstein-Barr virus, and 3 adenovirus post HSCT. Nine are alive, 1 died early post-transplant from CMV, and the other was a late death from pneumococcal sepsis. Patients with active mycobacterial infection at HSCT continued anti-mycobacterial therapy for almost 12 months. In conclusion, HSCT is a successful treatment for patients with mycobacterial susceptibility even with disseminated mycobacterial infection and in the absence of an HLA matched donor.

Mycobacterial diseases in patients with inborn errors of immunity

Clinical disease caused by the agent of tuberculosis, Mycobacterium tuberculosis, and by less virulent mycobacteria, such as bacillus Calmette-Guérin (BCG) vaccines and environmental mycobacteria, can result from inborn errors of immunity (IEIs). IEIs underlie more than 450 conditions, each associated with an impairment of the development and/or function of hematopoietic and/or non-hematopoietic cells involved in host defense. Only a minority of IEIs confer predisposition to mycobacterial disease. The IEIs underlying susceptibility to bona fide tuberculosis are less well delineated than those responsible for susceptibility to less virulent mycobacteria. However, all these IEIs share a defining feature: the impairment of immunity mediated by interferon gamma (IFN-γ). More profound IFN-γ deficiency is associated with a greater vulnerability to weakly virulent mycobacteria, whereas more selective IFN-γ deficiency is associated with a more selective predisposition to mycobacterial disease. We review here recent progress in the study of IEIs underlying mycobacterial diseases.

An updated review on Mendelian susceptibility to mycobacterial diseases - a silver jubilee celebration of its first genetic diagnosis

INTRODUCTION

Mendelian susceptibility to mycobacterial diseases (MSMD), a group of at least 18 different genetic disorders, encompasses a specific class of inborn errors of immunity that result in predilection to infection with mycobacteria including the weakly virulent strains. Primarily, these consist of defects in the IFN-γ-IL-12/23 circuit that is crucial for immunity against intracellular microorganisms. Although the first genetic etiology of MSMD was discovered in 1996, molecular diagnosis of MSMD in resource-constrained settings may remain far-fetched. Recently, original studies have emerged from developing countries, including India, wherein the genetic diagnosis was confirmed within the country itself. A lag of about 25 years, hence, seems to exist.

AREAS COVERED

Herein, we review the clinical, laboratory, and mutational profile of the genetic defects responsible for causing MSMD. We intend to enhance the recognition of these disorders in settings endemic for tuberculosis and bridge the gap between the developed and developing countries in the field of MSMD research and therapeutics.

EXPERT OPINION

Research in the field of MSMD in developing countries, including India, can uncover novel genetic etiologies, as the population exceeds 1.3 billion, a huge burden of tuberculosis (across all clinical spectrums) exists, and BCG vaccination is given universally at birth.

Genetic, Immunological, and Clinical Features of 32 Patients with Autosomal Recessive STAT1 Deficiency

Autosomal recessive (AR) STAT1 deficiency is a severe inborn error of immunity disrupting cellular responses to type I, II, and III IFNs, and IL-27, and conferring a predisposition to both viral and mycobacterial infections. We report the genetic, immunological, and clinical features of an international cohort of 32 patients from 20 kindreds: 24 patients with complete deficiency, and 8 patients with partial deficiency. Twenty-four patients suffered from mycobacterial disease (bacillus Calmette-Guérin = 13, environmental mycobacteria = 10, or both in 1 patient). Fifty-four severe viral episodes occurred in sixteen patients, mainly caused by Herpesviridae viruses. Attenuated live measles, mumps, and rubella and/or varicella zoster virus vaccines triggered severe reactions in the five patients with complete deficiency who were vaccinated. Seven patients developed features of hemophagocytic syndrome. Twenty-one patients died, and death was almost twice as likely in patients with complete STAT1 deficiency than in those with partial STAT1 deficiency. All but one of the eight survivors with AR complete deficiency underwent hematopoietic stem cell transplantation. Overall survival after hematopoietic stem cell transplantation was 64%. A diagnosis of AR STAT1 deficiency should be considered in children with mycobacterial and/or viral infectious diseases. It is important to distinguish between complete and partial forms of AR STAT1 deficiency, as their clinical outcome and management differ significantly.