Ludovic de Beaucoudrey

Mutations in STAT3 and IL12RB1 impair the development of human IL-17–producing T cells

The cytokines controlling the development of human interleukin (IL) 17–producing T helper cells in vitro have been difficult to identify. We addressed the question of the development of human IL-17–producing T helper cells in vivo by quantifying the production and secretion of IL-17 by fresh T cells ex vivo, and by T cell blasts expanded in vitro from patients with particular genetic traits affecting transforming growth factor (TGF) β, IL-1, IL-6, or IL-23 responses. Activating mutations in TGFB1, TGFBR1, and TGFBR2 (Camurati-Engelmann disease and Marfan-like syndromes) and loss-of-function mutations in IRAK4 and MYD88 (Mendelian predisposition to pyogenic bacterial infections) had no detectable impact. In contrast, dominant-negative mutations in STAT3 (autosomal-dominant hyperimmunoglobulin E syndrome) and, to a lesser extent, null mutations in IL12B and IL12RB1 (Mendelian susceptibility to mycobacterial diseases) impaired the development of IL-17–producing T cells. These data suggest that IL-12Rβ1– and STAT-3–dependent signals play a key role in the differentiation and/or expansion of human IL-17–producing T cell populations in vivo.

Gains of glycosylation comprise an unexpectedly large group of pathogenic mutations

Mutations involving gains of glycosylation have been considered rare, and the pathogenic role of the new carbohydrate chains has never been formally established. We identified three children with mendelian susceptibility to mycobacterial disease who were homozygous with respect to a missense mutation in IFNGR2 creating a new N-glycosylation site in the IFNγR2 chain. The resulting additional carbohydrate moiety was both necessary and sufficient to abolish the cellular response to IFNγ. We then searched the Human Gene Mutation Database for potential gain-of-N-glycosylation missense mutations; of 10,047 mutations in 577 genes encoding proteins trafficked through the secretory pathway, we identified 142 candidate mutations (∼1.4%) in 77 genes (∼13.3%). Six mutant proteins bore new N-linked carbohydrate moieties. Thus, an unexpectedly high proportion of mutations that cause human genetic disease might lead to the creation of new N-glycosylation sites. Their pathogenic effects may be a direct consequence of the addition of N-linked carbohydrate.

Novel STAT1 alleles in otherwise healthy patients with mycobacterial disease.

The transcription factor signal transducer and activator of transcription-1 (STAT1) plays a key role in immunity against mycobacterial and viral infections. Here, we characterize three human STAT1 germline alleles from otherwise healthy patients with mycobacterial disease. The previously reported L706S, like the novel Q463H and E320Q alleles, are intrinsically deleterious for both interferon gamma (IFNG)–induced gamma-activating factor–mediated immunity and interferon alpha (IFNA)–induced interferon-stimulated genes factor 3–mediated immunity, as shown in STAT1-deficient cells transfected with the corresponding alleles. Their phenotypic effects are however mediated by different molecular mechanisms, L706S affecting STAT1 phosphorylation and Q463H and E320Q affecting STAT1 DNA-binding activity. Heterozygous patients display specifically impaired IFNG-induced gamma-activating factor–mediated immunity, resulting in susceptibility to mycobacteria. Indeed, IFNA-induced interferon-stimulated genes factor 3–mediated immunity is not affected, and these patients are not particularly susceptible to viral disease, unlike patients homozygous for other, equally deleterious STAT1 mutations recessive for both phenotypes. The three STAT1 alleles are therefore dominant for IFNG-mediated antimycobacterial immunity but recessive for IFNA-mediated antiviral immunity at the cellular and clinical levels. These STAT1 alleles define two forms of dominant STAT1 deficiency, depending on whether the mutations impair STAT1 phosphorylation or DNA binding.

Bacillus Calmette guérin triggers the IL-12/IFN-γ axis by an IRAK-4- and NEMO-dependent, non-cognate interaction between monocytes, NK, and T lymphocytes

The IL‐12/IFN‐γ axis is crucial for protective immunity to Mycobacterium in humans and mice. Our goal was to analyze the relative contribution of various human blood cell subsets and molecules to the production of, or response to IL‐12 and IFN‐γ. We designed an assay for the stimulation of whole blood by live M. bovis Bacillus Calmette‐Guérin (BCG) alone, or BCG plus IL‐12 or IFN‐γ, measuring IFN‐γ and IL‐12 levels. We studied patients with a variety of specific inherited immunodeficiencies resulting in a lack of leukocytes, or T, B, and/or NK lymphocytes, or polymorphonuclear cells, or a lack of expression of key molecules such as HLA class II, CD40L, NF‐κB essential modulator (NEMO), and IL‐1 receptor‐associated kinase‐4 (IRAK‐4). Patients with deficiencies in IL‐12p40, IL‐12 receptor β1 chain (IL‐12Rβ1), IFN‐γR1, IFN‐γR2, and STAT‐1 were used as internal controls. We showed that monocytes were probably the main producers of IL‐12, and that NK and T cells produced similar amounts of IFN‐γ. NEMO and IRAK‐4 were found to be important for IL‐12 production and subsequent IFN‐γ production, while a lack of CD40L or HLA class II had no major impact on the IL‐12/IFN‐γ axis. The stimulation of whole blood by live BCG thus triggers the IL‐12/IFN‐γ axis by an IRAK‐4‐ and NEMO‐dependent, non‐cognate interaction between monocytes, NK, and T lymphocytes.

Paracoccidioides brasiliensis Disseminated Disease in a Patient with Inherited Deficiency in the β1 Subunit of the Interleukin (IL)–12/IL-23 Receptor

BACKGROUND Paracoccidioides brasiliensis is a facultative intracellular dimorphic fungus that causes paracoccidioidomycosis (PCM), the most important deep mycosis in Latin America. Only a small percentage of individuals infected by P. brasiliensis develop clinical PCM, possibly in part because of genetically determined interindividual variability of host immunity. However, no primary immunodeficiency has ever been associated with PCM. METHODS We describe the first patient, to our knowledge, with PCM and a well-defined primary immunodeficiency in the beta 1 subunit of the interleukin (IL)-12/IL-23 receptor, a disorder previously shown to be specifically associated with impaired interferon (IFN)-gamma production, mycobacteriosis, and salmonellosis. RESULTS Our patient had a childhood history of bacille Calmette-Guérin disease and nontyphoid salmonellosis and, at the age of 20 years, presented to our clinic with a disseminated (acute) form of PCM. He responded well to antifungal treatment and is now doing well at 24 years of age. CONCLUSIONS This unique observation supports previous studies of PCM suggesting that IL-12, IL-23, and IFN-gamma play an important role in protective immunity to P. brasiliensis. Tuberculosis and PCM are thus not only related clinically and pathologically, but also by their immunological pathogenesis. Our study further expands the spectrum of clinical manifestations of inherited defects of the IL-12/IL-23-IFN-gamma axis. Patients with unexplained deep fungal infections, such as PCM, should be tested for defects in the IL-12/IL-23-IFN- gamma axis.

The NEMO mutation creating the most-upstream premature stop codon is hypomorphic because of a reinitiation of translation.

Amorphic mutations in the NF- kappa B essential modulator (NEMO) cause X-dominant incontinentia pigmenti, which is lethal in males in utero, whereas hypomorphic mutations cause X-recessive anhidrotic ectodermal dysplasia with immunodeficiency, a complex developmental disorder and life-threatening primary immunodeficiency. We characterized the NEMO mutation 110_111insC, which creates the most-upstream premature translation termination codon (at codon position 49) of any known NEMO mutation. Surprisingly, this mutation is associated with a pure immunodeficiency. We solve this paradox by showing that a Kozakian methionine codon located immediately downstream from the insertion allows the reinitiation of translation. The residual production of an NH(2)-truncated NEMO protein was sufficient for normal fetal development and for the subsequent normal development of skin appendages but was insufficient for the development of protective immune responses.

Interleukin-12 Receptor β1 Chain Deficiency in a Child with Disseminated Tuberculosis

An 11-year-old girl who presented with disseminated tuberculosis associated with secondary hemophagocytosis received a diagnosis of interleukin-12 receptor beta 1 chain deficiency. This diagnosis of immunodeficiency should, therefore, be considered for children with disseminated tuberculosis, even in the absence of any personal or familial history of prior infection by weakly pathogenic Salmonella and Mycobacterium species.

Inherited disorders of the IL-12-IFN-γ axis in patients with disseminated BCG infection

Disseminated BCG infection is a rare complication of vaccination that occurs in patients with impaired immunity. In recent years, a series of inherited disorders of the IL-12-IFN-γ axis have been described that predispose affected individuals to disseminated disease caused by BCG, environmental Mycobacteria, and non-typhoidal Salmonella. The routine immunological work-up of these patients is normal and the diagnosis requires specific investigation of the IL-12-IFN-γ circuit. We report here the first two such patients originating from and living in Iran. The first child is two years old and suffers from complete IFN-γ receptor 2 deficiency and disseminated BCG infection. He is currently in clinical remission thanks to prolonged multiple antibiotic therapy. The other, a 28-year-old adult, suffers from IL-12p40 deficiency and presented with disseminated BCG infection followed by recurrent episodes of systemic salmonellosis. He is now doing well. A third patient of Iranian descent, living in North America, was reported elsewhere to suffer from IL-12Rβ1 deficiency. These three patients thus indicate that various inherited defects of the IL-12-IFN-γ circuit can be found in Iranian people. In conclusion we recommend to consider the disorders of the IL-12-IFN-γ circuit in all patients with severe BCG infection, disseminated environmental mycobacterial disease, or systemic non-typhoidal salmonellosis, regardless of their ethnic origin and country of residence.

A novel X-linked recessive form of Mendelian susceptibility to mycobaterial disease

Background: Mendelian susceptibility to mycobacterial disease (MSMD) is associated with infection caused by weakly virulent mycobacteria in otherwise healthy people. Causal germline mutations in five autosomal genes (IFNGR1, IFNGR2, STAT1, IL12RB1, IL12B) and one X-linked (NEMO) gene have been described. The gene products are physiologically related, as they are involved in interleukin 12/23-dependent, interferon γ-mediated immunity. However, no genetic aetiology has yet been identified for about half the patients with MSMD. Methods: A large kindred was studied, including four male maternal relatives with recurrent mycobacterial disease, suggesting X-linked recessive inheritance. Three patients had recurrent disease caused by the bacille Calmette–Guérin vaccine, and the fourth had recurrent tuberculosis. The infections showed tropism for the peripheral lymph nodes. Results: Known autosomal and X-linked genetic aetiologies of MSMD were excluded through genetic and immunological investigations. Genetic linkage analysis of the X-chromosome identified two candidate regions, on Xp11.4–Xp21.2 and Xq25–Xq26.3, with a maximum LOD score of 2. Conclusion: A new X-linked recessive form of MSMD is reported, paving the way for the identification of a new MSMD-causing gene.

T Cell-Dependent Activation of Dendritic Cells Requires IL-12 and IFN-γ Signaling in T Cells

Patients presenting with genetic deficiencies in IFNGR1, IFNGR2, IL-12B, and IL-12RB1 display increased susceptibility to mycobacterial infections. We analyzed in this group of patients the cross-talk between human CD4+ T lymphocytes and dendritic cells (DCs) that leads to maturation of DC into producers of bioactive IL-12 and to activation of T cells into IFN-γ producers. We found that this cross-talk is defective in all patients from this group. Unraveling the mechanisms underlying this deficiency, we showed that IL-12 signaling in T cells is required to induce expression of costimulatory molecules and secretion of IL-12 by DCs and that IFNGR expression is required on both DCs and CD4+ T cells to induce IL-12 secretion by DCs. These data suggest that CD4+ T cell-mediated activation of DCs plays a critical role in the defense against mycobacterial infections in humans.