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.

Disseminated Mycobacterium simiae Infection in a Patient with Complete IL-12p40 Deficiency.

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare group of genetic disorders characterized by infections with weakly virulent environmental mycobacteria (EM) or Mycobacterium bovis bacillus Calmette-Guérin (BCG). Herein, we described the case of a 4.5-year-old boy with protein-losing enteropathy, lymphoproliferation, and candidiasis, who was found to have disseminated Mycobacterium simiae infection. A homozygous mutation in the IL12B gene, c.527_528delCT (p.S176Cfs*12) was identified, responsible for the complete IL-12p40 deficiency. He was resistant to anti-mycobacterial treatment and finally died due to sepsis-related complications.

Interleukin 12p40 Deficiency Promotes Abdominal Aortic Aneurysm by Activating CCN2/MMP2 Pathways.

Background Development of abdominal aortic aneurysm (AAA) is associated with proinflammatory cytokines including interleukin-12 (IL12). Deficiency of interleukin 12p40 (IL12p40) increases localized fibrotic events by promoting TGFß2 (transforming growth factor ß)-dependent anti-inflammatory response. Here, we determined whether IL12p40 deficiency in apolipoprotein E-/- mice attenuates the development of AAA by antagonizing proinflammatory response. Methods and Results Double knockout (DKO) mice were generated by crossbreeding IL12p40-/- mice with apolipoprotein E-/- mice (n=12). Aneurysmal studies were performed using angiotensin II (1 µg/kg/min; subcutaneous). Surprisingly, DKO mice did not prevent the development of AAA with angiotensin II infusion. Immunohistological analysis, however, showed distinct pathological features between apolipoprotein E-/- and DKO mice. Polymerase chain reaction (7 day) and cytokine arrays (28 day) of the aortic tissues from DKO mice showed significantly increased expression of cytokines related to anti-inflammatory response (interleukin 5 and interleukin 13), synthetic vascular smooth muscle cell phenotype (Activin receptor-like kinase-1 (ALK-1), artemin, and betacellulin) and T helper 17-associated response (4-1BB, interleukin-17e (Il17e) and Cd40 ligand (Cd-40L)). Indeed, DKO mice exhibited increased expression of the fibro-proteolytic pathway in the medial layer of aortae induced by cellular communication network factor 2 (CCN2) and Cd3+IL17+ cells compared with apolipoprotein E-/- mice. Laser capture microdissection showed predominant expression of CCN2/TGFß2 in the medial layer of human AAA. Finally, Ccn2 haploinsufficiency in the mice showed decreased AAA incidence in response to elastase infusion, associated with decreased matrix metalloproteinase-2 expression. Conclusions Our study reveals novel roles for IL12p40 deficiency in inducing fibro-proteolytic activities in the aneurysmal mouse model. Mechanistically, these effects of IL12p40 deficiency are mediated by CCN2/matrix metalloproteinase-2 crosstalk in the medial layer of aneurysmal aortae.

Interleukin-12/23 deficiency differentially affects pathology in male and female Alzheimer's disease-like mice.

Pathological aggregation of amyloid-ß (Aß) is a main hallmark of Alzheimer's disease (AD). Recent genetic association studies have linked innate immune system actions to AD development, and current evidence suggests profound gender differences in AD pathogenesis. Here, we characterise gender-specific pathologies in the APP23 AD-like mouse model and find that female mice show stronger amyloidosis and astrogliosis compared with male mice. We tested the gender-specific effect of lack of IL12p40, the shared subunit of interleukin (IL)-12 and IL-23, that we previously reported to ameliorate pathology in APPPS1 mice. IL12p40 deficiency gender specifically reduces Aß plaque burden in male APP23 mice, while in female mice, a significant reduction in soluble Aß1-40 without changes in Aß plaque burden is seen. Similarly, plasma and brain cytokine levels are altered differently in female versus male APP23 mice lacking IL12p40, while glial properties are unchanged. These data corroborate the therapeutic potential of targeting IL-12/IL-23 signalling in AD, but also highlight the importance of gender considerations when studying the role of the immune system and AD.

[Disseminated infection caused by the bacillus Calmette-Guérin vaccine and SARS-CoV-2 coinfection in a patient with IL-12 receptor ß1 subunit deficiency]. / Infección diseminada por vacuna con bacilo de Calmette-Guérin y coinfección por SARS-CoV-2 en paciente con deficiencia de la subunidad ß1 del receptor de IL-12.

BACKGROUND: Inborn errors of immunity manifest with a greater susceptibility to infections, autoimmunity, autoinflammatory diseases, allergies, or malignancies. One of these is the mendelian susceptibility to mycobacterial disease. The most frequent etiology is the complete autosomal recessive deficiency of the ß1 subunit of the interleukin 12 receptor. CASE REPORT: A female patient who, by the age of six months, started with a nodular lesion in the right shoulder and ipsilateral axillary adenitis after the bacillus Calmette-Guérin vaccine was applied. Later, she developed a cutaneous fistula in the anterior thorax, the inframammary region, and chronic recidivant suppurative lymphadenitis. A disseminated infection caused by Mycobacterium bovis was diagnosed, therefore, individualized pharmacological treatment was required due to failure with the primary treatment. The patient was diagnosed with deficiency in the ß1 subunit of the interleukin 12 receptor at age six. During her last hospitalization, she presented fever, cough, and tachypnea, and SARS-CoV-2 was detected by quantitative polymerase chain reaction. The patient has had a favorable evolution. CONCLUSION: In patients with disseminated infections caused by bacillus Calmette-Guérin vaccination or by environmental mycobacteria, there should be suspicion of an inborn error of immunity and the patient should be referred to a third level hospital for an early immunological assessment.

Antecedentes: Los errores innatos de la inmunidad se manifiestan con una mayor susceptibilidad a infecciones, autoinmunidad, enfermedades autoinflamatorias, alergia o malignidad. Uno de estos es la susceptibilidad mendeliana a infecciones micobacterianas. La etiología más frecuente es la deficiencia completa autosómica recesiva de la subunidad ß1 del receptor de interleucina 12. Caso clínico: Paciente que comenzó a los seis meses de edad con una lesión nodular en hombro derecho y adenitis axilar ipsolateral posterior a la vacuna con bacilo de Calmette-Guérin. Posteriormente desarrolló una fistula cutánea en tórax anterior, región inframamaria y linfadenitis supurativa crónica recidivante. Se diagnosticó infección diseminada por Mycobacterium bovis, por lo que requirió tratamiento farmacológico individualizado debido al fracaso con el tratamiento primario. La paciente fue diagnosticada con deficiencia de la subunidad ß1 del receptor de interleucina 12 a los seis años. Durante su última hospitalización presentó fiebre, tos y taquipnea, detectándose SARS-CoV-2 por reacción en cadena de la polimerasa cuantitativa. La paciente evolucionó favorablemente. Conclusión: En los pacientes con infecciones diseminadas por la vacuna con bacilo de Calmette-Guérin o micobacterias ambientales, debe sospecharse un error innato de la inmunidad y derivarlos a tercer nivel de atención para la evaluación inmunológica temprana.

Deficiency of IL12p40 (Interleukin 12 p40) Promotes Ang II (Angiotensin II)-Induced Abdominal Aortic Aneurysm.

Objective- Abdominal aortic aneurysm is caused by the accumulation of inflammatory cells in the aortic wall. Our recent studies demonstrated that inhibition of Notch signaling attenuates abdominal aortic aneurysm formation by shifting the macrophage balance towards anti-inflammatory (M2) phenotype. Using IL12p40-/- (interleukin 12 p40) mice, we investigated the effects of M2-predominant macrophages on the development of abdominal aortic aneurysm. Approach and Results- Male (8-10 week-old) wild-type and IL12p40-/- mice (n=15) on C57BL/6 background were infused with Ang II (angiotensin II, 1000 ng/kg per minute) by implanting osmotic pumps subcutaneously for 28 days. In the IL12p40-/- mice, Ang II significantly increased the maximal intraluminal diameter (9/15) as determined by transabdominal ultrasound imaging. In addition, IL12p40-deletion significantly increased aortic stiffness in response to Ang II as measured by pulse wave velocity and atomic force microscopy. Histologically, IL12p40-/- mice exhibited increased maximal external diameter of aorta and aortic lesions associated with collagen deposition and increased elastin fragmentation compared with wild-type mice infused with Ang II. Mechanistically, IL12p40 deficiency by siRNA (small interfering RNA) augmented the Tgfß2-mediated Mmp2 expression in wild-type bone marrow-derived macrophages without affecting the expression of Mmp9. No such effects of IL12p40 deficiency on MMP2/MMP9 was observed in human aortic smooth muscle cells or fibroblasts. Depletion of macrophages in IL12p40-/- mice by clodronate liposomes significantly decreased the maximal external diameter of aorta and aortic stiffness in response to Ang II as determined by imaging and atomic force microscopy. Conclusions- IL12p40 depletion promotes the development of abdominal aortic aneurysm, in part, by facilitating recruitment of M2-like macrophages and potentiating aortic stiffness and fibrosis mediated by Tgfß2.

Chronic Disseminated Salmonellosis in a Patient With Interleukin-12p40 Deficiency.

Interleukin (IL)-12 is composed of p35 and p40 subunits; in this case, IL-12p40 deficiency is a rare genetic etiology of Mendelian susceptibility to mycobacterial disease. Salmonellosis has been reported in almost half of these patients and mostly present in recurrent extraintestinal form. In this report, we described an 18-month-old boy with absence of IL-12p40 production suffering from chronic disseminated nontyphoidal salmonellosis. To the best of our knowledge, this is the first-reported case.

Visceral leishmaniasis in two patients with IL-12p40 and IL-12Rß1 deficiencies.

Mutations of the IL12B and IL12RB1 genes underlie the development of IL-12 p40 and IL-12Rß1 deficiencies, respectively, both of which cause predisposition to infection with weakly virulent mycobacteria and Salmonella. Infections with other intramacrophagic organisms have only been rarely observed. We identified two patients with visceral leishmaniasis who had autosomal recessive IL-12 p40 and IL-12Rß1 deficiencies, respectively. This finding demonstrates the importance of IFN-γ immunity in the control of leishmaniasis. We also searched the literature for similar reports in patients with these and other primary immunodeficiencies.

IL-12p40 gene-deficient BALB/c mice exhibit lower weight loss, reduced lung pathology and decreased sensitization to allergen in response to infection with pneumonia virus of mice.

Respiratory syncytial virus (RSV) is a major cause of bronchiolitis and pneumonia in infants and pneumonia virus of mice (PVM) causes similar disease. BALB/c mice are highly susceptible, while C57BL/6 mice are more resistant to PVM. IL-12 was significantly more up-regulated in response to PVM infection in BALB/c than in C57BL/6 mice. IL-12p40-deficient neonatal and adult BALB/c mice showed significantly less weight loss than wild-type mice after PVM challenge. The percentage of regulatory T cells, as well as IFN-ß and IL-18 expression, was higher in the lungs of both neonatal and adult IL-12p40-/- mice. Adult IL-12p40-/- mice also showed enhanced TGF-ß and IL-10 expression and reduced inflammatory responses. Furthermore, IL-12p40-/- mice showed decreased sensitization to inhaled cockroach antigen after PVM infection when compared to wild-type mice. In conclusion, these data suggest that a depressed regulatory capacity in BALB/c mice to PVM infection results in enhanced immunopathology and sensitization to allergen.

IL-12p40 impairs mesenchymal stem cell-mediated bone regeneration via CD4+ T cells.

Severe or prolonged inflammatory response caused by infection or biomaterials leads to delayed healing or bone repair failure. This study investigated the important roles of the proinflammatory cytokines of the interleukin-12 (IL-12) family, namely, IL-12 and IL-23, in the inflammation-mediated inhibition of bone formation in vivo. IL-12p40-/- mice lacking IL-12 and IL-23 exhibited enhanced bone formation. IL-12 and IL-23 indirectly inhibited bone marrow mesenchymal stem cell (BMMSC) differentiation by stimulating CD4+ T cells to increase interferon γ (IFN-γ) and IL-17 levels. Mechanistically, IL-17 synergistically enhanced IFN-γ-induced BMMSC apoptosis. Moreover, INF-γ and IL-17 exerted proapoptotic effects by upregulating the expression levels of Fas and tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), as well as by activating the caspase cascade in BMMSCs. IL-12p40 depletion in mice could promote ectopic bone formation. Thus, IL-12p40 is an attractive therapeutic target to overcome the inflammation-mediated inhibition of bone formation in vivo.

Essential Role of Interleukin-12/23p40 in the Development of Graft-versus-Host Disease in Mice.

Graft-versus-host disease (GVHD), in both its acute (aGVHD) and chronic (cGVHD) forms, remains a major obstacle impeding successful allogeneic hematopoietic stem cell transplantation (allo-HSCT). T cells, in particular pathogenic T helper (Th) 1 and Th17 subsets, are a driving force for the induction of GVHD. IL-12 and IL-23 cytokines share a common p40 subunit and play a critical role in driving Th1 differentiation and in stabilizing the Th17 phenotype, respectively. In our current study, we hypothesized that p40 is an essential cytokine in the development of GVHD. By using p40-deficient mice, we found that both donor- and host-derived p40 contribute to the development of aGVHD. Neutralization of p40 with an anti-p40 mAb inhibited Th1- and Th17-polarization in vitro. Furthermore, anti-p40 treatment reduced aGVHD severity while preserving the graft-versus-leukemia (GVL) activity. Alleviation of aGVHD was associated with an increase of Th2 differentiation and a decrease of Th1 and Th17 effector T cells in the GVHD target organs. In addition, anti-p40 treatment attenuated the severity of sclerodermatous cGVHD. These results provide a strong rationale that blockade of p40 may represent a promising therapeutic strategy in preventing and treating aGVHD and cGVHD while sparing the GVL effect after allo-HSCT.

Tissue specific CD4+ T cell priming determines the requirement for interleukin-23 in experimental arthritis.

INTRODUCTION: Rheumatoid arthritis (RA) is a chronic inflammatory disease with striking heterogeneity in (i) clinical presentation, (ii) autoantibody profiles and (iii) responses to treatment suggesting that distinct molecular mechanisms may underlie the disease process. Proteoglycan-induced arthritis (PGIA) is induced by two pathways either by intraperitoneal (i.p.) or subcutaneous (s.c.) exposure to PG. CD4+ T cells primed by the i.p. route are T helper (Th)1 cells expressing interferon gamma (IFN-γ) whereas CD4+ T cells primed by the s.c. route are Th17 cells expressing interleukin (IL)-17. IL-23 is necessary for maintaining the phenotype of Th17 cells; however, IL-23 is inflammatory independent of IL-17. The aim of this study was to determine if PGIA induced by different routes of immunization is dependent on IL-23. METHODS: BALB/c wild type (WT), IL-12p40-/- and IL-23p19-/- littermate mice were immunized with recombinant G1 (rG1) domain of human PG in adjuvant either i.p. or s.c. and development of arthritis monitored. Joint histology was assessed. CD4+ T cell cytokines in spleen, lymph node (LN), and joint were assessed by intracellular staining and cytokine enzyme-linked immunosorbent assay. RNA transcripts for cytokines and transcription factors were examined. RESULTS: PGIA was suppressed in the p40-/- and p19-/- mice immunized by the s.c. route but only inhibited in p40-/- mice by the i.p. route. The joints of s.c. but not i.p. sensitized mice contained a population of CD4+ T cells expressing single positive IFN-γ and IL-17 and double positive IFN-γ/IL-17 which were dependent on IL-23 expression. The IFN-γ and IL-17 response in spleen and inguinal LN was inhibited in p19-/- mice and p40-/- mice after s.c. immunization, whereas in i.p. immunized p19-/- mice, IL-17 but not IFN-γ was reduced. Inguinal LN CD11c+ dendritic cells (DC) from s.c. immunized, but not spleen DC from i.p. immunized mice, produced IL-23, IL-1ß, and IL-6 and activated T cells to produce IL-17. CONCLUSION: IL-23 is necessary for the activity of Th17 after s.c. immunization and does not play a role independent of IL-17 after i.p. immunization. These data demonstrate that the molecular pathways IL-23/17 and IL-12/IFN-γ may represent subtypes of arthritis determined by the mode of induction.

MyD88 and TLR9 dependent immune responses mediate resistance to Leishmania guyanensis infections, irrespective of Leishmania RNA virus burden.

Infections with Leishmania parasites of the Leishmania Viannia subgenus give rise to both localized cutaneous (CL), and metastatic leishmaniasis. Metastasizing disease forms including disseminated (DCL) and mutocutaneous (MCL) leishmaniasis result from parasitic dissemination and lesion formation at sites distal to infection and have increased inflammatory responses. The presence of Leishmania RNA virus (LRV) in L. guyanensis parasites contributes to the exacerbation of disease and impacts inflammatory responses via activation of TLR3 by the viral dsRNA. In this study we investigated other innate immune response adaptor protein modulators and demonstrated that both MyD88 and TLR9 played a crucial role in the development of Th1-dependent healing responses against L. guyanensis parasites regardless of their LRV status. The absence of MyD88- or TLR9-dependent signaling pathways resulted in increased Th2 associated cytokines (IL-4 and IL-13), which was correlated with low transcript levels of IL-12p40. The reliance of IL-12 was further confirmed in IL12AB-/- mice, which were completely susceptible to infection. Protection to L. guyanensis infection driven by MyD88- and TLR9-dependent immune responses arises independently to those induced due to high LRV burden within the parasites.

A 1,100-year-old founder effect mutation in IL12B gene is responsible for Mendelian susceptibility to mycobacterial disease in Tunisian patients.

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare disorder predisposing apparently healthy individuals to infections caused by weakly virulent mycobacteria such as bacille Calmette-Guerin (BCG), environmental mycobacteria, and poorly virulent Salmonella strains. IL-12p40 deficiency is the first reported human disease due to a cytokine gene defect and is one of the deficiencies that cause MSMD. Nine mutant alleles only have been identified in the IL12B gene, and three of them are recurrent mutations due to a founder effect in specific populations. IL-12p40 deficiency has been identified especially in countries where consanguinity is high and where BCG vaccination at birth is universal. We investigated, in such settings, the clinical, cellular, and molecular features of six IL-12p40-deficient Tunisian patients having the same mutation in IL12B gene (c.298_305del). We found that this mutation is inherited as a common founder mutation arousing ~1,100 years ago. This finding facilitates the development of a preventive approach by genetic counseling and prenatal diagnosis especially in affected families.

Principal role of IL-12p40 in the decreased Th1 and Th17 responses driven by dendritic cells of mice lacking IL-12 and IL-18.

IL-12 and IL-18 are cytokines which are mainly secreted by endothelial cells and monocytes including dendritic cells. The well-known effects of IL-12 and IL-18 in the protection against bacteria and virus infection as well as tumor development are associated with their characteristics in synergistically driving the development of T helper type 1 (Th1) cells and inducing IFN-γ production. In this study, we compared the knockout effects of IL-12 and/or IL-18 genes on phenotypes and functional capabilities of dendritic cells (DCs) including their ability to polarize naive CD4(+) T cells. The expression levels of surface molecules such as MHC II, CD80, CD86 and ICOSL, and endocytic capacity were not significantly differences between DCs of wild type (WT) mice and double knockout (DKO) mice of IL-12p40 and IL-18. Additionally, DCs lacking IL-12p40 and/or IL-18 genes were equivalently efficient in inducing T cell proliferation, compared with the WT-DCs. Interestingly, IL-10 production significantly decreased in DKO-DCs, while production of other inflammation-related cytokines were unaffected in WT-DCs and DKO-DCs. Importantly, IL-12p40(-/-)-DCs and DKO-DCs severely impaired the ability to induce IFN-γ and IL-17 production from CD4(+) T cells. IL-18(-/-)-DCs also moderately decreased IL-17 production and IL-17-expressing CD4(+) T cells when co-cultured with CD4(+) T cells, demonstrating the involvement of IL-18 in driving IL-17 differentiation. Taken together, these results suggest the principal contribution of IL-12p40 in inducing Th1 and Th17 polarization, regardless of similar surface phenotypes of DCs.

Antiangiogenic therapy promoted metastasis of hepatocellular carcinoma by suppressing host-derived interleukin-12b in mouse models.

Antiangiogenic therapy, specially sorafenib, has become the standard of care for patients with advanced hepatocellular carcinoma (HCC), however, the improvement in survival time is not satisfactory. Previous studies have found that, in some circumstances, antiangiogenic therapy promoted tumor metastasis and the mechanistic studies were mainly focus on cancer-cell-autonomous manners. In two experimental metastasis models with tail-vein injection with hepatoma cells and an orthotopic HCC mouse model, we found that pretreatment with two vascular endothelial growth factor receptor (VEGFR) inhibitors, sunitinib and sorafenib, facilitated tumor cell survival in blood stream and promoted lung metastasis from tumors that were subsequently incubated after drug discontinuation, indicating that host response joined into the pro-metastatic effects. An antibody microarray identified that interleukin (IL)-12b was decreased in the peripheral blood of the mice treated with the two VEGFR inhibitors. IL-12b suppression in macrophages and dendritic cells from host organs was found to play a crucial role in treatment-induced metastasis. Supplement with recombinant mouse IL-12b or restoration of IL-12b expression in the host by zoledronic acid, which was previously reported to enhance IL-12 expression in vitro and in vivo, alleviated the metastasis-promoting effects of sunitinib and sorafenib. These studies suggest that host response to VEGFR inhibitors facilitates HCC metastasis and restoration of IL-12b expression could translate into clinical benefits.

Inherited IL-12p40 deficiency: genetic, immunologic, and clinical features of 49 patients from 30 kindreds.

Autosomal recessive interleukin (IL)-12 p40 (IL-12p40) deficiency is a rare genetic etiology of mendelian susceptibility to mycobacterial disease (MSMD). We report the genetic, immunologic, and clinical features of 49 patients from 30 kindreds originating from 5 countries (India, Iran, Pakistan, Saudi Arabia, and Tunisia). There are only 9 different mutant alleles of the IL12B gene: 2 small insertions, 3 small deletions, 2 splice site mutations, and 1 large deletion, each causing a frameshift and leading to a premature stop codon, and 1 nonsense mutation. Four of these 9 variants are recurrent, affecting 25 of the 30 reported kindreds, due to founder effects in specific countries. All patients are homozygous and display complete IL-12p40 deficiency. As a result, the patients lack detectable IL-12p70 and IL-12p40 and have low levels of interferon gamma (IFN-γ). The clinical features are characterized by childhood onset of bacille Calmette-Guérin (attenuated Mycobacterium bovis strain) (BCG) and Salmonella infections, with recurrences of salmonellosis (36.4%) more common than recurrences of mycobacterial disease (25%). BCG vaccination led to BCG disease in 40 of the 41 patients vaccinated (97.5%). Multiple mycobacterial infections were rare, observed in only 3 patients, whereas the association of salmonellosis and mycobacteriosis was observed in 9 patients. A few other infections were diagnosed, including chronic mucocutaneous candidiasis (n = 3), nocardiosis (n = 2), and klebsiellosis (n = 1). IL-12p40 deficiency has a high but incomplete clinical penetrance, with 33.3% of genetically affected relatives of index cases showing no symptoms. However, the prognosis is poor, with mortality rates of up to 28.6%. Overall, the clinical phenotype of IL-12p40 deficiency closely resembles that of interleukin 12 receptor ß1 (IL-12Rß1) deficiency. In conclusion, IL-12p40 deficiency is more common than initially thought and should be considered worldwide in patients with MSMD and other intramacrophagic infectious diseases, salmonellosis in particular.

IL-12p40 deficiency leads to uncontrolled Trypanosoma cruzi dissemination in the spinal cord resulting in neuronal death and motor dysfunction.

Chagas' disease is a protozoosis caused by Trypanosoma cruzi that frequently shows severe chronic clinical complications of the heart or digestive system. Neurological disorders due to T. cruzi infection are also described in children and immunosuppressed hosts. We have previously reported that IL-12p40 knockout (KO) mice infected with the T. cruzi strain Sylvio X10/4 develop spinal cord neurodegenerative disease. Here, we further characterized neuropathology, parasite burden and inflammatory component associated to the fatal neurological disorder occurring in this mouse model. Forelimb paralysis in infected IL-12p40KO mice was associated with 60% (p<0.05) decrease in spinal cord neuronal density, glutamate accumulation (153%, p<0.05) and strong demyelization in lesion areas, mostly in those showing heavy protein nitrosylation, all denoting a neurotoxic degenerative profile. Quantification of T. cruzi 18S rRNA showed that parasite burden was controlled in the spinal cord of WT mice, decreasing from the fifth week after infection, but progressive parasite dissemination was observed in IL-12p40KO cords concurrent with significant accumulation of the astrocytic marker GFAP (317.0%, p<0.01) and 8-fold increase in macrophages/microglia (p<0.01), 36.3% (p<0.01) of which were infected. Similarly, mRNA levels for CD3, TNF-α, IFN-γ, iNOS, IL-10 and arginase I declined in WT spinal cords about the fourth or fifth week after infection, but kept increasing in IL-12p40KO mice. Interestingly, compared to WT tissue, lower mRNA levels for IFN-γ were observed in the IL-12p40KO spinal cords up to the fourth week of infection. Together the data suggest that impairments of parasite clearance mechanisms in IL-12p40KO mice elicit prolonged spinal cord inflammation that in turn leads to irreversible neurodegenerative lesions.

Interleukin-12p40 modulates human metapneumovirus-induced pulmonary disease in an acute mouse model of infection.

The mechanisms that regulate the host immune response induced by human metapneumovirus (hMPV), a newly-recognized member of the Paramyxoviridae family, are largely unknown. Cytokines play an important role in modulating inflammatory responses during viral infections. IL-12p40, a known important mediator in limiting lung inflammation, is induced by hMPV and its production is sustained after the resolution phase of infection suggesting that this cytokine plays a role in the immune response against hMPV. In this work, we demonstrated that in mice deficient in IL-12p40, hMPV infection induced an exacerbated pulmonary inflammatory response and mucus production, altered cytokine response, and decreased lung function. However, hMPV infection in these mice does not have an effect on viral replication. These results identify an important regulatory role of IL-12p40 in hMPV infection.

IL-12Rß2 is essential for the development of experimental cerebral malaria.

A Th1 response is required for the development of Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM). The role of pro-Th1 IL-12 in malaria is complex and controversial. In this study, we addressed the role of IL-12Rß2 in ECM development. C57BL/6 mice deficient for IL-12Rß2, IL-12p40, or IL-12p35 were analyzed for ECM development after blood-stage PbA infection in terms of ischemia and blood flow by noninvasive magnetic resonance imaging and angiography, T cell recruitment, and gene expression. Without IL-12Rß2, no neurologic sign of ECM developed upon PbA infection. Although wild-type mice developed distinct brain microvascular pathology, ECM-resistant, IL-12Rß2-deficient mice showed unaltered cerebral microcirculation and the absence of ischemia after PbA infection. In contrast, mice deficient for IL-12p40 or IL-12p35 were sensitive to ECM development. The resistance of IL-12Rß2-deficient mice to ECM correlated with reduced recruitment of activated T cells and impaired overexpression of lymphotoxin-α, TNF-α, and IFN-γ in the brain after PbA infection. Therefore, IL-12Rß2 signaling is essential for ECM development but independent from IL-12p40 and IL-12p35. We document a novel link between IL-12Rß2 and lymphotoxin-α, TNF-α, and IFN-γ expression, key cytokines for ECM pathogenesis.