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The human genetic basis of tuberculosis (TB) has long remained elusive. We recently reported a high level of enrichment in homozygosity for the common TYK2 P1104A variant in a heterogeneous cohort of patients with TB from non-European countries in which TB is endemic. This variant is homozygous in ∼1/600 Europeans and ∼1/5,000 people from other countries outside East Asia and sub-Saharan Africa. We report a study of this variant in the UK Biobank cohort. The frequency of P1104A homozygotes was much higher in patients with TB (6/620, 1%) than in controls (228/114,473, 0.2%), with an odds ratio (OR) adjusted for ancestry of 5.0 [95% confidence interval (CI): 1.96–10.31, P = 2 × 10−3]. Conversely,we did not observe enrichment for P1104A heterozygosity, or for TYK2 I684S or V362F homozygosity or heterozygosity. Moreover, it is unlikely that more than 10% of controls were infected with Mycobacterium tuberculosis, as 97% were of European genetic ancestry, born between 1939 and 1970, and resided in the United Kingdom. Had all of them been infected, the OR for developing TB upon infection would be higher. These findings suggest that homozygosity for TYK2 P1104A may account for ∼1% of TB cases in Europeans.

Mendelian susceptibility to mycobacterial disease (MSMD) is characterized by a selective predisposition to clinical disease caused by the Bacille Calmette-Guérin (BCG) vaccine and environmental mycobacteria. The known genetic etiologies of MSMD are inborn errors of IFN-γ immunity due to mutations of 15 genes controlling the production of or response to IFN-γ. Since the first MSMD-causing mutations were reported in 1996, biallelic mutations in the genes encoding IFN-γ receptor 1 (IFN-γR1) and IFN-γR2 have been reported in many patients of diverse ancestries. Surprisingly, mutations of the gene encoding the IFN-γ cytokine itself have not been reported, raising the remote possibility that there might be other agonists of the IFN-γ receptor. We describe 2 Lebanese cousins with MSMD, living in Kuwait, who are both homozygous for a small deletion within the IFNG gene (c.354_357del), causing a frameshift that generates a premature stop codon (p.T119Ifs4*). The mutant allele is loss of expression and loss of function. We also show that the patients' herpesvirus Saimiri-immortalized T lymphocytes did not produce IFN-γ, a phenotype that can be rescued by retrotransduction with WT IFNG cDNA. The blood T and NK lymphocytes from these patients also failed to produce and secrete detectable amounts of IFN-γ. Finally, we show that human IFNG has evolved under stronger negative selection than IFNGR1 or IFNGR2, suggesting that it is less tolerant to heterozygous deleterious mutations than IFNGR1 or IFNGR2. This may account for the rarity of patients with autosomal-recessive, complete IFN-γ deficiency relative to patients with complete IFN-γR1 and IFN-γR2 deficiencies.

ISG15 is an Interferon (IFN)-α/β—inducible, ubiquitin-like intracellular protein. Its conjugation to various proteins (ISGylation) contributes to antiviral immunity in mice. Here, we describe human patients with inherited ISG15 deficiency and mycobacterial, but not viral, diseases. The lack of intracellular ISG15 production and protein ISGylation was not associated with cellular susceptibility to any viruses that we tested, consistent with the lack of viral diseases in these patients. By contrast, the lack of mycobacterium-induced ISG15 secretion by leukocytes—granulocyte, in particular—reduced the production of IFN-γ by lymphocytes, including natural killer cells, probably accounting for the enhanced susceptibility to mycobacterial disease. This experiment of nature shows that human ISGylation is largely redundant for antiviral immunity, but that ISG15 plays an essential role as an IFN-γ-inducing secreted molecule for optimal antimycobacterial immunity.

ISG15 is a well-known intracellular ubiquitin-like molecule involved in ISGylation. However, a recent study has revived the notion first put forward two decades ago that ISG15 is also a secreted molecule. Human neutrophils, monocytes and lymphocytes can release ISG15, even though this protein has no detectable signal peptide sequence. ISG15 has also been found in the secretory granules of granulocytes. The mechanism underlying ISG15 secretion is unknown. Secreted ISG15 acts on at least T and natural killer (NK) lymphocytes, in which it induces interferon (IFN)-γ production. However, the mechanism by which ISG15 stimulates these cells also remains unclear. ISG15 and IFN-γ seem to define an innate circuit that operates preferentially, but not exclusively, between granulocytes and NK cells. Inherited ISG15 deficiency is associated with severe mycobacterial disease in both mice and humans. This infectious phenotype probably results from the lack of secreted ISG15, because patients and mice with other inborn errors of IFN-γ immunity also display mycobacterial diseases. In addition to raising mechanistic issues, the studies described here pave the way for clinical studies of various aspects, ranging from the use of recombinant ISG15 in patients with infectious diseases to the use of ISG15-blocking agents in patients with inflammatory diseases. Immunology: An antiviral protein's role in antibacterial defense ISG15, a protein previously implicated in protection against viruses in mice, is now emerging as an important defense against mycobacteria in humans. In a review article, Dusan Bogunovic and his colleagues discuss recent research - much of it stemming from the scientists' own laboratory at The Rockefeller University, USA - showing that ISG15 is released by the immune system in response to mycobacterial species. Secretion of ISG15 in turn induces specialized immune cells known as lymphocytes to produce interferon-gamma, an immune-activating molecule that is essential for fighting mycobacterial infections, such as tuberculosis. People with mutations in the gene encoding ISG15 express low levels of interferon-gamma in their white blood cells and are highly prone to infection from otherwise poorly pathogenic mycobacterial bugs. The authors raise the possibility of modulating ISG15 levels as a way to combat infectious and inflammatory diseases.

Genetic variants underlying life-threatening diseases, being unlikely to be transmitted to the next generation, are gradually and selectively eliminated from the population through negative selection. We study the determinants of this evolutionary process in human genes underlying monogenic diseases by comparing various negative selection scores and an integrative approach, CoNeS, at 366 loci underlying inborn errors of immunity (IEI). We find that genes underlying autosomal dominant (AD) or X-linked IEI have stronger negative selection scores than those underlying autosomal recessive (AR) IEI, whose scores are not different from those of genes not known to be disease causing. Nevertheless, genes underlying AR IEI that are lethal before reproductive maturity with complete penetrance have stronger negative selection scores than other genes underlying AR IEI. We also show that genes underlying AD IEI by loss of function have stronger negative selection scores than genes underlying AD IEI by gain of function, while genes underlying AD IEI by haploinsufficiency are under stronger negative selection than other genes underlying AD IEI. These results are replicated in 1,140 genes underlying inborn errors of neurodevelopment. Finally, we propose a supervised classifier, SCoNeS, which predicts better than state-of-the-art approaches whether a gene is more likely to underlie an AD or AR disease. The clinical outcomes of monogenic inborn errors, together with their mode and mechanisms of inheritance, determine the levels of negative selection at their corresponding loci. Integrating scores of negative selection may facilitate the prioritization of candidate genes and variants in patients suspected to carry an inborn error.

Monocytes and dendritic cells regulate adaptive and innate immunity. This study uncovers an association between mutations in the gene encoding interferon regulatory factor 8 and deficiency of dendritic cells and monocytes in the context of disseminated bacille Calmette–Guérin disease. The discovery of human primary immunodeficiencies that affect the development of granulocytes, B cells, and T cells has been instrumental in defining the contribution of these cell types to protective immunity. 1 , 2 Monocytes, macrophages, and dendritic cells — all mononuclear phagocytes — have essential functions in both innate and acquired immunity. These cells initially recognize and engulf invading microbes, produce proinflammatory cytokines (e.g., interleukin-12), and process antigens for presentation to naive T cells, which consequently secrete various lymphokines (e.g., interferon-γ). 3 , 4 On activation by cytokines secreted by T cells, mononuclear phagocytes destroy ingested microorganisms. There are no known genetic causes . . .

Purpose Inborn errors of immunity (IEI) are typically monogenic. Data from the Indian subcontinent are relatively scarce. This paper evaluates IEI diagnosed in Sri Lanka. Methods Data of patients diagnosed with IEI from 2010 to 2022 at the Department of Immunology, Medical Research Institute, Colombo, Sri Lanka, were retrospectively analyzed. Results Two hundred and six patients were diagnosed with IEI, with a prevalence of 0.94 per 100,000. The onset of disease was below 12 years in 84.9%, whereas in 10.9%, it was after 18 years. The male: female ratio was 1.78:1. Consanguinity was identified in 26.6%. IEI were found in all but one (bone marrow failure) of the 10 IUIS categories. Predominantly antibody deficiencies were the most common category among the nine identified (30.1%), followed by combined immune deficiencies with syndromic features (21.3%), immunodeficiencies affecting cellular and humoral immunity (19.9%), congenital defects of phagocyte number or function (13.1%), and defects in intrinsic and innate immunity (8.2%). Severe combined immune deficiency (SCID) was the commonest disease (14.6%), followed by chronic granulomatous disease (CGD) (10.6%) and X linked agammaglobulinemia (8.7%). Of the patients with a known outcome ( n  = 184), 51 died (27.7%). Mortality rates were high in SCID (83.3%), Omenn syndrome (OS) (100%), and CGD (31.8%) patients. Conclusion IEI in Sri Lanka are diagnosed mainly in childhood. The low diagnosis rates suggest a need for educating clinicians regarding IEI in adulthood. The high mortality rates associated with some IEI indicate the need of transplant services in the country.

On evaluation at our centre 2 months after initiation of treatment, we noted progression of the multifocal tuberculosis (figure 1). (C) Chest CT scan showing a 24 mm subcarinal low-density adenopathy and bilateral hilar adenopathies and (D) on coronal reconstructions (lung windows), bronchus intermedius and right lower lobe endobronchial granulomas resulting in air trapping of the right lower lobe. Severe multifocal tuberculosis was diagnosed, with well-known risk factors: high-dose oral corticosteroids, history of severe measles and poor adherence to treatment.

BACKGROUNDNatural resistance to Mycobacterium tuberculosis (Mtb) infection in some people with HIV (PWH) is unexplained.METHODSWe performed single cell RNA-sequencing of bronchoalveolar lavage cells, unstimulated or ex vivo stimulated with Mtb, for 7 PWH who were tuberculin skin test (TST) and IFN-γ release assay (IGRA) positive (called LTBI) and 6 who were persistently TST and IGRA negative (called resisters).RESULTSAlveolar macrophages (AM) from resisters displayed a baseline M1 macrophage phenotype while AM from LTBI did not. Resisters displayed alveolar lymphocytosis, with enrichment of all T cell subpopulations including IFNG-expressing cells. In both groups, mycobactericidal granulysin was expressed almost exclusively by a T cell subtype that coexpressed granzyme B, perforin and NK cell receptors. These poly-cytotoxic T lymphocytes (poly-CTL) overexpressed activating NK cell receptors and were increased in resister BAL. Following challenge with Mtb, only intraepithelial lymphocyte-like cells from LTBI participants responded with increased transcription of IFNG. AM from resisters responded with a stronger TNF signature at 6 hours after infection while at 24 hours after infection, AM from LTBI displayed a stronger IFN-γ signature. Conversely, at 24 hours after infection, only AM from resisters displayed an upregulation of MHC class I polypeptide-related sequence A (MICA) transcripts, which encode an activating ligand for poly-CTL.CONCLUSIONThese results suggest that poly-CTL and M1-like pre-activated AM mediate the resister phenotype in PWH.FUNDINGNational Institutes of Health. Canadian Institutes of Health Research. Digital Research Alliance of Canada. French National Research Agency. French National Agency for Research on AIDS and Viral Hepatitis. St. Giles Foundation. General Atlantic Foundation. South African Medical Research Council Centre for Tuberculosis Research.

A 51-year-old Iranian man presented with severe CMV infection, which proved to be fatal over the next 29 months. Investigation determined that he had a homozygous frameshift mutation in the gene encoding a nonfunctional NOS2 protein.