Human host genetic factors in mycobacterial and Salmonella infection: lessons from single gene disorders in IL-12/IL-23-dependent signaling that affect innate and adaptive immunity

The Interleukins Orchestrate Mucosal Immune Responses to Salmonella Infection in the Intestine

Salmonella infection remains one of the major public health problems in the world, with increasing resistance to antibiotics. The resolution is to explore the pathogenesis of the infection and search for alternative therapy other than antibiotics. Immune responses to Salmonella infection include innate and adaptive immunity. Flagellin or muramyl dipeptide from Salmonella, recognized by extracellular Toll-like receptors and intracellular nucleotide-binding oligomerization domain2, respectively, induce innate immunity involving intestinal epithelial cells, neutrophils, macrophages, dendric cells and lymphocytes, including natural killer (NK) and natural killer T (NKT) cells. The cytokines, mostly interleukins, produced by the cells involved in innate immunity, stimulate adaptive immunity involving T and B cells. The mucosal epithelium responds to intestinal pathogens through its secretion of inflammatory cytokines, chemokines, and antimicrobial peptides. Chemokines, such as IL-8 and IL-17, recruit neutrophils into the cecal mucosa to defend against the invasion of Salmonella, but induce excessive inflammation contributing to colitis. Some of the interleukins have anti-inflammatory effects, such as IL-10, while others have pro-inflammatory effects, such as IL-1β, IL-12/IL-23, IL-15, IL-18, and IL-22. Furthermore, some interleukins, such as IL-6 and IL-27, exhibit both pro- and anti-inflammatory functions and anti-microbial defenses. The majority of interleukins secreted by macrophages and lymphocytes contributes antimicrobial defense or protective effects, but IL-8 and IL-10 may promote systemic Salmonella infection. In this article, we review the interleukins involved in Salmonella infection in the literature.

Mycobacterium Intracellulare Infection Associated with TYK2 Deficiency: A Case Report and Review of the Literature

Individuals with genetic defects show an increased susceptibility to poorly pathogenic mycobacteria including nontuberculous mycobacteria and Bacillus Calmette-Guerin (BCG). In previous studies, defects in multiple genes were identified to be associated with mycobacterium infection including tyrosine kinase 2 (TYK2). The mutations lead to insufficient production of interferon (IFN)-γ or an insufficient response to IFN-α/β, interleukin (IL)-6, IL-10, IL-12 and IL-23. Herein, we describe a case of Mycobacterium intracellulare infection in a male with abdominal pain and diarrhea. Whole exome sequencing of the genomes revealed a compound heterozygous mutation (c.3083A>G/c.2590C>T, p.N1028S/p.R864C) in the TYK2 gene. The patient recovered after two years of anti-mycobacterial treatment and no relapse was observed so far. We also reviewed 24 cases of mycobacterial infection associated with TYK2 deficiency which provides evidence of how personalised genomics can improve outcomes.

Same species, different diseases: how and why typhoidal and non-typhoidal Salmonella enterica serovars differ

Human infections by the bacterial pathogen Salmonella enterica represent major disease burdens worldwide. This highly ubiquitous species consists of more than 2600 different serovars that can be divided into typhoidal and non-typhoidal Salmonella (NTS) serovars. Despite their genetic similarity, these two groups elicit very different diseases and distinct immune responses in humans. Comparative analyses of the genomes of multiple Salmonella serovars have begun to explain the basis of the variation in disease manifestations. Recent advances in modeling both enteric fever and intestinal gastroenteritis in mice will facilitate investigation into both the bacterial- and host-mediated mechanisms involved in salmonelloses. Understanding the genetic and molecular mechanisms responsible for differences in disease outcome will augment our understanding of Salmonella pathogenesis, host immunity, and the molecular basis of host specificity. This review outlines the differences in epidemiology, clinical manifestations, and the human immune response to typhoidal and NTS infections and summarizes the current thinking on why these differences might exist.

Transcriptional profiling of hilar nodes from pigs after experimental infection with Actinobacillus pleuropneumoniae

The gram-negative bacterium Actinobacillus pleuropneumoniae (APP) is an inhabitant of the porcine upper respiratory tract and the causative agent of porcine pleuropneumonia (PP). In recent years, knowledge about the proinflammatory cytokine and chemokine gene expression that occurs in lung and lymph node of the APP-infected swine has been advanced. However, systematic gene expression profiles on hilar nodes from pigs after infection with Actinobacillus pleuropneumoniae have not yet been reported. The transcriptional responses were studied in hilar nodes (HN) from swine experimentally infected with APP and the control groupusing Agilent Porcine Genechip, including 43,603 probe sets. 9,517 transcripts were identified as differentially expressed (DE) at the p ≤ 0.01 level by comparing the log2 (normalized signal) of the two groups named treatment group (TG) and controls (CG). Eight hundred and fifteen of these DE transcripts were annotated as pig genes in the GenBank database (DB). Two hundred and seventy-two biological process categories (BP), 75 cellular components and 171 molecular functions were substantially altered in the TG compared to CG. Many BP were involved in host immune responses (i.e., signaling, signal transmission, signal transduction, response to stimulus, oxidation reduction, response to stress, immune system process, signaling pathway, immune response, cell surface receptor linked signaling pathway). Seven DE gene pathways (VEGF signaling pathway, Long-term potentiation, Ribosome, Asthma, Allograft rejection, Type I diabetes mellitus and Cardiac muscle contraction) and statistically significant associations with host responses were affected. Many cytokines (including NRAS, PI3K, MAPK14, CaM, HSP27, protein phosphatase 3, catalytic subunit and alpha isoform), mediating the proliferation and migration of endothelial cells and promoting survival and vascular permeability, were activated in TG, whilst many immunomodulatory cytokines were suppressed. The significant changes in the expression patterns of the genes, GO terms, and pathways, led to a decrease of antigenic peptides with antigen presenting cells presented to T lymphocytes via the major histocompatibility complex, and alleviated immune response induced APP of HN. The immune response ability of HN in the APP-infected pigs was weakened; however, cell proliferation and migration ability was enhanced.

Nontuberculous mycobacterial infections in children with inborn errors of the immune system

Severe mycobacterial disease is mostly confined to patients who are immunocompromized either by acquired or inherited causes. One such genetic disorder is Mendelian Susceptibility to Mycobacterial Disease (MSMD), a hot topic within the field of primary immunodeficiency. This single gene disorder is characterized by isolated infection with mycobacteria or Salmonella due to a defect in the type-1 cytokine response. In the last two decades, ten genes have been labeled as causing MSMD when they harbor germline mutations, namely IL12B, IL12RB1, IFNGR1, IFNGR2, STAT1, IKBKG, CYBB, TYK2, IRF8 and ISG15. The mutations lead to either insufficient production of IFN-γ, or to an insufficient response to the cytokine. Current treatment options include recombinant IFN-γ and hematologic stem cell transplantation (HSCT). In the future, gene therapy, antisense-mediated exon skipping and chemical intervention in glycosylation problems may become successful alternatives. Furthermore, it is likely that many new candidate genes and pathways crucial for mycobacterial immunity will be identified.

Long-term safety of ustekinumab in patients with moderate-to-severe psoriasis: final results from 5 years of follow-up

BACKGROUND

Long-term safety evaluations of biologics are needed to inform patient management decisions.

OBJECTIVES

To evaluate the safety of ustekinumab in patients with moderate-to-severe psoriasis treated for up to 5 years.

METHODS

Safety data were pooled from four studies of ustekinumab for psoriasis. Rates of adverse events (AEs), serious AEs (SAEs) and AEs of interest [infections, nonmelanoma skin cancers (NMSCs), other malignancies and major adverse cardiovascular events (MACE)] per 100 patient-years (PY) of follow-up were analysed by ustekinumab dose (45 or 90 mg) and by year of follow-up (years 1-5) to evaluate the dose response and impact of cumulative exposure. Observed rates of overall mortality and other malignancies were compared with those expected in the general U.S. population.

RESULTS

Analyses included 3117 patients (8998 PY) who received one or more doses of ustekinumab, with 1482 patients treated for ≥4 years (including 838 patients ≥5 years). At year 5, event rates (45 mg, 90 mg, respectively) for overall AEs (242·6, 225·3), SAEs (7·0, 7·2), serious infections (0·98, 1·19), NMSCs (0·64, 0·44), other malignancies (0·59, 0·61) and MACE (0·56, 0·36) were comparable between dose groups. Year-to-year variability was observed, but no increasing trend was evident. Rates of overall mortality and other malignancies were comparable with those expected in the general U.S. population.

CONCLUSIONS

No dose-related or cumulative toxicity was observed with increasing duration of ustekinumab exposure for up to 5 years. Rates of AEs reported in ustekinumab psoriasis trials are generally comparable with those reported for other biologics approved for the treatment of moderate-to-severe psoriasis.

IL-12Rβ1 deficiency: mutation update and description of the IL12RB1 variation database

IL-12Rβ1 deficiency is an autosomal recessive disorder characterized by predisposition to recurrent and/or severe infections caused by otherwise poorly pathogenic mycobacteria and salmonella. IL-12Rβ1 is a receptor chain of both the IL-12 and the IL-23 receptor and deficiency of IL-12Rβ1 thus abolishes both IL-12 and IL-23 signaling. IL-12Rβ1 deficiency is caused by bi-allelic mutations in the IL12RB1 gene. Mutations resulting in premature stop codons, such as nonsense, frame shift, and splice site mutations, represent the majority of IL-12Rβ1 deficiency causing mutations (66%; 46/70). Also every other morbid mutation completely inactivates the IL-12Rβ1 protein. In addition to disease-causing mutations, rare and common variations with unknown functional effect have been reported in IL12RB1. All these variants have been deposited in the online IL12RB1 variation database (www.LOVD.nl/IL12RB1). In this article, we review the function of IL-12Rβ1 and molecular genetics of human IL12RB1.

IL12B expression is sustained by a heterogenous population of myeloid lineages during tuberculosis

IL12B is required for resistance to Mycobacterium tuberculosis (Mtb) infection, promoting the initiation and maintenance of Mtb-specific effector responses. While this makes the IL12-pathway an attractive target for experimental tuberculosis (TB) therapies, data regarding what lineages express IL12B after infection is established are limited. This is not obvious in the lung, an organ in which both hematopoietic and non-hematopoietic lineages produce IL12p40 upon pathogen encounter. Here, we use radiation bone marrow chimeras and Yet40 reporter mice to determine what lineages produce IL12p40 during experimental TB. We observed that hematopoietic IL12p40-production was sufficient to control Mtb, with no contribution by non-hematopoietic lineages. Furthermore, rather than being produced by a single subset, IL12p40 was produced by cells that were heterogenous in their size, granularity, autofluorescence and expression of CD11c, CD11b and CD8α. While depending on the timepoint and tissue examined, the surface phenotype of IL12p40-producers most closely resembled macrophages based on previous surveys of lung myeloid lineages. Importantly, depletion of CD11c(hi) cells during infection had no affect on lung IL12p40-concentrations. Collectively, our data demonstrate that IL12p40 production is sustained by a heterogenous population of myeloid lineages during experimental TB, and that redundant mechanisms of IL12p40-production exist when CD11c(hi) lineages are absent.

Disseminated Mycobacterium genavense infection in a patient with a novel partial interleukin-12/23 receptor β1 deficiency

A patient presented with late onset disseminated nontuberculous mycobacterium (NTM) infection due to a novel interleukin-12/interleukin-23 receptor β1 (IL-12/IL-23Rβ1) mutation, r.1561C>G, leading to the amino acid substitution R521G. This is the second patient reported with a partial IL-12/IL-23Rβ1 defect.

Glutathione deficiency in type 2 diabetes impairs cytokine responses and control of intracellular bacteria

Individuals with type 2 diabetes are at increased risk of acquiring melioidosis, a disease caused by Burkholderia pseudomallei infection. Although up to half of melioidosis patients have underlying diabetes, the mechanisms involved in this increased susceptibility are unknown. We found that B. pseudomallei-infected PBMCs from diabetic patients were impaired in IL-12p70 production, which resulted in decreased IFN-γ induction and poor bacterial killing. The defect was specific to the IL-12-IFN-γ axis. Defective IL-12 production was also observed during Mycobacterium tuberculosis infection, in which diabetes is likewise known to be a strong risk factor. In contrast, IL-12 production in diabetic cells was not affected upon Salmonella enterica infection or in response to TLR2, -3, -4, and -5 ligands. Poor IL-12 production correlated with a deficiency in intracellular reduced glutathione (GSH) concentrations in diabetic patients. Addition of GSH or N-acetylcysteine to PBMCs selectively restored IL-12 and IFN-γ production and improved bacterial killing. Furthermore, the depletion of GSH in mice led to increased susceptibility to melioidosis, reduced production of IL-12p70, and poorer disease outcome. Our data thus establish a link between GSH deficiency in diabetes and increased susceptibility to melioidosis that may open up new therapeutic avenues to protect diabetic patients against some intracellular bacterial pathogens.

Identification of a common immune signature in murine and human systemic Salmonellosis

Despite the importance of Salmonella infections in human and animal health, the target antigens of Salmonella-specific immunity remain poorly defined. We have previously shown evidence for antibody-mediating protection against invasive Salmonellosis in mice and African children. To generate an overview of antibody targeting in systemic Salmonellosis, a Salmonella proteomic array containing over 2,700 proteins was constructed and probed with immune sera from Salmonella-infected mice and humans. Analysis of multiple inbred mouse strains identified 117 antigens recognized by systemic antibody responses in murine Salmonellosis. Importantly, many of these antigens were independently identified as target antigens using sera from Malawian children with Salmonella bacteremia, validating the study of the murine model. Furthermore, vaccination with SseB, the most prominent antigenic target in Malawian children, provided mice with significant protection against Salmonella infection. Together, these data uncover an overlapping immune signature of disseminated Salmonellosis in mice and humans and provide a foundation for the generation of a protective subunit vaccine.

Molecular and cellular characterization of a Salmonella enterica serovar Paratyphi a outbreak strain and the human immune response to infection

Enteric fever is an invasive life-threatening systemic disease caused by the Salmonella enterica human-adapted serovars Typhi and Paratyphi. Increasing incidence of infections with Salmonella enterica serovar Paratyphi A and the spreading of its antibiotic-resistant derivates pose a significant health concern in some areas of the world. Herein, we describe a molecular and phenotypic characterization of an S. Paratyphi A strain accounted for a recent paratyphoid outbreak in Nepal that affected at least 37 travelers. Pulsed-field gel electrophoresis analysis of the outbreak isolates revealed one genetic clone (pulsotype), confirming a single infecting source. Genetic profiling of the outbreak strain demonstrated the contribution of specific bacteriophages as a prime source of genetic diversity among clinical isolates of S. Paratyphi A. Phenotypic characterization in comparison with the S. Paratyphi A ATCC 9150 reference sequenced strain showed differences in flagellar morphology and increased abilities of the outbreak strain with respect to its motility, invasion into nonphagocytic cells, intracellular multiplication, survival within macrophages, and higher induction of interleukin-8 (IL-8) secreted by host cells. Collectively, these differences suggest an enhanced virulence potential of this strain and demonstrate an interesting phenotypic variation among S. Paratyphi A isolates. In vivo profiling of 16 inflammatory cytokines in patients infected with the outbreak strain revealed a common profile of a remarkable gamma interferon (IFN-γ) induction together with elevated concentrations of tumor necrosis factor alpha (TNF-α), IL-6, IL-8, IL-10, and IL-15, but not IL-12, which was previously demonstrated as elevated in nontyphoidal Salmonella infections. This apparent profile implies a distinct immune response to paratyphoid infections.

Development of protective immunity to Salmonella, a mucosal pathogen with a systemic agenda

Salmonella infections can cause a range of intestinal and systemic diseases in human and animal hosts. Although some Salmonella serovars initiate a localized intestinal inflammatory response, others use the intestine as a portal of entry to initiate a systemic infection. Considerable progress has been made in understanding bacterial invasion and dissemination strategies, as well as the nature of the Salmonella-specific immune response to oral infection. Innate and adaptive immunity are rapidly initiated after oral infection, but these effector responses can also be hindered by bacterial evasion strategies. Furthermore, although Salmonella resides within intramacrophage phagosomes, recent studies have highlighted a surprising collaboration of CD4 Th1, Th17, and B-cell responses in mediating resistance to Salmonella infection.

Clinical and host genetic characteristics of Mendelian susceptibility to mycobacterial diseases in Japan

PURPOSE

The aim of this study is to investigate clinical characteristics and genetic backgrounds of Mendelian susceptibility to mycobacterial diseases (MSMD) in Japan.

METHODS

Forty-six patients diagnosed as having MSMD were enrolled in this study. All patients were analyzed for the IFNGR1, IFNGR2, IL12B, IL12RB1, STAT1, and NEMO gene mutations known to be associated with MSMD.

RESULTS

Six patients and one patient were diagnosed as having partial interferon-γ receptor 1 deficiency and nuclear factor-κB-essential modulator deficiency, respectively. Six of the seven patients had recurrent disseminated mycobacterial infections, while 93% of the patients without these mutations had only one episode of infection.

CONCLUSIONS

The patients with a genetic mutation were more susceptible to developing recurrent disseminated mycobacterial infections. Recurrent disseminated mycobacterial infections occurred in a small number of patients even without these mutations, suggesting the presence of as yet undetermined genetic factors underlying the development and progression of this disease.

Mendelian susceptibility to mycobacterial disease

The host response to mycobacterial infection is mediated by the type I cytokine pathway (cell-mediated immunity). Deficiencies in this response result in susceptibility to poorly pathogenic mycobacterial species such as bacille Calmette-Guérin and environmental mycobacteria. In recent years a number of mutations in the genes encoding major components in the type I cytokine axis have been described which predispose to disseminated infection with these weakly virulent mycobacterial species. Affected individuals are also prone to extra-intestinal disease caused by non-typhoidal Salmonella. The genes involved display a high level of allelic heterogeneity, accounting for a number of distinct genetic disorders which vary in their mode of inheritance and clinical presentation. These disorders have been termed Mendelian susceptibility to mycobacterial disease and are discussed in this review article.

IL23R and IL12B SNPs and Haplotypes Strongly Associate with Crohn's Disease Risk in a New Zealand Population

DNA samples from 339 Crohn's disease (CD) and 407 randomly selected controls from the Auckland (New Zealand) IBD project, were genotyped for five common single nucleotide polymorphisms in IL-23R (rs11805303, rs7517847, rs1343151, rs11209026, and rs10889677) and two in IL-12B (rs1363670 and rs6887695). While the IL-12B variants did not show an overall association and other IL23R variants led to minor changes in the risk of CD, rs1343151 and/or rs7517847 variants in the IL-23R gene strongly reduced the risk of developing CD at both allelic and genotype levels. A significantly decreased risk of first diagnosis of childhood CD was observed in individuals carrying the A allele of rs1343151, or between 17–40 y in individuals carrying the G allele in rs7517847 of IL-23R. A significantly decreased risk of ileocolonic or structuring disease was observed in individuals carrying the A allele in either rs11209026 or rs1343151, or the G allele in rs7517847 of IL-23R, and when such individuals did develop the disease, they were unlikely to require a bowel resection. Certain haplotypes very strongly modified risk. There was evidence for interactions of IL-23R variants with the NOD2 wild-type (d/d) genotype. Down-regulating the function of the IL-23R gene may decrease CD risk in the normal population.

Review of ustekinumab, an interleukin-12 and interleukin-23 inhibitor used for the treatment of plaque psoriasis

The pathogenesis of psoriasis is unknown, although it is generally accepted that this chronic inflammatory skin disorder is a complex autoimmune condition similar to other T-cell mediated disorders. Psoriasis imposes a heavy burden on the lifestyle of those affected due to the psychological, arthritic, and cutaneous morbidities; thus significant research has focused on the genetic and immunologic features of psoriasis in anticipation of more targeted, efficacious, and safe therapies. Recently, CD4(+) T helper (Th) 17 cells and interleukins (IL)-12 and -23 have been important in the pathogenesis of T-cell mediated disorders such as psoriasis and has influenced the development of medications that specifically target these key immunological players. Ustekinumab is a monoclonal antibody belonging to a newly developed class of biological, anti-cytokine medications that notably targets the p40 subunit of both IL-12 and -23, both naturally occurring proteins that are important in regulating the immune system and are understood to play a role in immune-mediated inflammatory disorders. Ustekinumab's safety and efficacy has been evaluated for the treatment of moderate-to-severe plaque psoriasis in 3 phase III clinical trials, 2 placebo-controlled (PHOENIX 1 and 2), and 1 comparator-controlled (ACCEPT) study which proved advantageous in patients who were treatment-naive, previously failed other immunosuppressive medications including cyclosporine or methotrexate, were unresponsive to phototherapy, or were unable to use or tolerate other therapies. Ustekinumab has also been investigated for other indications such as psoriatic arthritis, Crohn's disease, and relapsing/remitting multiple sclerosis. We present a concise review evaluating the evidence that supports the use of ustekinumab in the treatment of plaque psoriasis and other conditions.

Mycobacterium bovis BCG-itis and cervical lymphadenitis due to Salmonella enteritidis in a patient with complete interleukin-12/-23 receptor beta1 deficiency

Mendelian susceptibility to mycobacterial disease (MSMD) is a rare disorder with predisposition to severe, sometimes lethal, disease caused by otherwise poorly virulent, non-tuberculous environmental mycobacteria and poorly virulent salmonellae. In patients with MSMD, mutations have been identified in five genes that encode for the proteins IL-12/IL-23p40, IL-12/ IL-23Rbeta1, IFN-R1, IFN-gammaR2 and STAT1. These proteins play important roles in the type-1 cytokine pathway, which is crucial for human host defence against intracellular pathogens such as mycobacteria and salmonellae. We report a girl with mild Mycobacterium bovis Bacille Calmette-Guérin (BCG) disease and Salmonella enteritidis cervical lymphadenitis. Despite treatment, she has remained a fecal carrier of S. enteritidis for the past 14 years. She was found to have complete IL-12/IL-23Rbeta1 deficiency. A homozygous r.518G>C IL12RB1 mutation was identified, leading to a non-functional R173P substitution in the IL-12/IL-23Rbeta1 protein. This mutation abrogated IL-12/IL-23Rbeta1 cell-surface expression and resulted in complete lack of T cell responsiveness to both IL-12 and IL-23.

Salmonella induced IL-23 and IL-1beta allow for IL-12 production by monocytes and Mphi1 through induction of IFN-gamma in CD56 NK/NK-like T cells

Background

The type-1 cytokine pathway plays a pivotal role in immunity against intracellular bacterial pathogens such as Salmonellae and Mycobacteria. Bacterial stimulation of pattern recognition receptors on monocytes, macrophages and dendritic cells initiates this pathway, and results in the production of cytokines that activate lymphocytes to produce interferon (IFN)-γ. Interleukin (IL)-12 and IL-23 are thought to be the key cytokines required for initiating a type-1 cytokine immune response to Mycobacteria and Salmonellae. The relative contribution of IL-23 and IL-12 to this process is uncertain.

Methodology/Principal Findings

We show that various TLR agonists induce the production of IL-23 but not IL-12 in freshly isolated human monocytes and cultured human macrophages. In addition, type 1 pro-inflammatory macrophages (Mϕ1) differentiated in the presence of GM-CSF and infected with live Salmonella produce IL-23, IL-1β and IL-18, but not IL-12. Supernatants of Salmonella-infected Mϕ1 contained more IL-18 and IL-1β as compared with supernatants of Mϕ1 stimulated with isolated TLR agonists, and induced IFN-γ production in human CD56⁺ cells in an IL-23 and IL-1β-dependent but IL-12-independent manner. In addition, IL-23 together with IL-18 or IL-1β led to the production of GM-CSF in CD56⁺ cells. Both IFN-γ and GM-CSF enhanced IL-23 production by monocytes in response to TLR agonists, as well as induced IL-12 production.

Conclusions/Significance

The findings implicate a positive feedback loop in which IL-23 can enhance its release via induction of IFN-γ and GM-CSF. The IL-23 induced cytokines allow for the subsequent production of IL-12 and amplify the IFN-γ production in the type-1 cytokine pathway.

Genetic deficiencies of innate immune signalling in human infectious disease

The type-1 cytokine (interleukin 12, interleukin 23, interferon gamma, interleukin 17) signalling pathway is triggered during infection by activation of phagocyte-expressed pattern-recognition receptors that recognise specific pathogen-associated molecular patterns. Triggering of this pathway results, among other things, in activation of microbicidal mechanisms in phagocytic cells. Individuals with a deficiency in one of the proteins in the pathway are unusually susceptible to otherwise poorly pathogenic, mostly environmental, mycobacteria and salmonellae. Individuals with deficiencies in other innate immune signalling proteins show unusual susceptibility to pathogens other than mycobacteria or salmonellae. We discuss recent insights into key molecules involved in type-1 cytokine signalling pathways and provide an update on the molecular genetic defects underlying mendelian susceptibility to mycobacterial disease. We also discuss deficiencies in the innate immune signalling proteins that lead to susceptibility to other pathogens. Knowledge of innate immune signalling has allowed the identification of defects in such patients. However, some patients have enhanced susceptibility to pathogens even though no mutations have been found in the candidate genes identified thus far. Whereas a few patients might have autoantibodies against type-1 cytokines, others might harbour mutations in new genes and pathways that still need to be identified.

IL-23 modulates CD56+/CD3- NK cell and CD56+/CD3+ NK-like T cell function differentially from IL-12

NK and NK-like T cells play an essential role in linking innate and adaptive immunity through their ability to secrete IFN-gamma. The exact trigger initiating production of IFN-gamma is uncertain. Antigen-presenting cell (APC)-derived IL-12 is thought to be the classical IFN-gamma-inducing cytokine but requires an additional stimulus such as IFN-gamma itself. IL-23 and IL-18 are among the first cytokines secreted by APC in response to binding of pathogen-associated molecular patterns such as LPS. Thus, early APC-derived IL-23 may be an initial trigger of IFN-gamma production in NK and NK-like T cells. Herein, we characterized the effect of IL-23 on IFN-gamma secretion by NK and NK-like T cells. Our findings show that IL-23 and IL-18 synergistically elicit IFN-gamma production in NK-like T cells but not in NK cells. In contrast, IL-12 together with IL-18-induced secretion of IFN-gamma in both populations. The observed synergy between IL-23 and IL-18 in NK-like T cells coincided with IL-23-mediated up-regulation of IL-18Ralpha. Furthermore, IL-23 up-regulated CD56 expression in NK-like T cells and, together with IL-18, induced proliferation of NK and NK-like T cells. We postulate a role for APC-derived IL-23 in the activation of NK and NK-like T cells early in infection and in shaping T(h)1 differentiation, via induction of IFN-gamma, which provides the additional stimulus needed for APC to subsequently produce IL-12.

Exposure of cord blood to Mycobacterium bovis BCG induces an innate response but not a T-cell cytokine response

Despite routine vaccination with Mycobacterium bovis bacillus Calmette-Guérin (BCG) soon after birth, tuberculosis in babies and adults remains epidemic in South Africa. The immune responses of the naïve newborn child and how they are affected by vaccination with BCG are as yet not fully understood. Immunity during pregnancy and in healthy human newborns may be skewed toward type 2 cytokine production; however, it is type 1 cytokines that are required for protection against M. tuberculosis infection. To better understand neonatal cytokine responses prior to and following exposure to mycobacteria, we have collected cord blood and peripheral blood samples and evaluated the cytokine response following ex vivo incubation with BCG. Gamma interferon (IFN-gamma), interleukin 10 (IL-10), IL-12, and low levels of IL-13 and IL-5 but no IL-4 were secreted into the culture supernatant of cord blood mononuclear cells. Intracellular staining showed that IL-10 and IL-12 were produced by monocytes and that IFN-gamma was produced by natural killer (NK) cells but not by CD4(+) or CD8(+) T cells. In contrast, in the peripheral blood samples collected from babies 13 weeks post-BCG vaccination, IFN-gamma was detected within CD4(+) and CD8(+) cells. Taken together, the data suggest a central role for Th1 cytokines in naïve as well as BCG-vaccinated neonates in the protective immune response to tuberculosis. NK cell-derived IFN-gamma produced in naïve neonates likely plays a key protective role via monocyte activation and the priming of a subsequent adaptive Th1 response.

Salmonella infections in immunocompromised adults

Clinical syndromes caused by Salmonella infection in humans are divided into typhoid fever, caused by Salmonella typhi and Salmonella paratyphi, and a range of clinical syndromes, including diarrhoeal disease, caused by a large number of non-typhoidal salmonella serovars (NTS). Typhoid is a human-restricted and highly adapted invasive disease, but shows little association with immunocompromise. In contrast, NTS have a broad vertebrate host range, epidemiology that often involves food animals, and have a dramatically more severe and invasive presentation in immunocompromised adults, in particular in the context of HIV. Immunocompromise among adults, including underlying severe or progressive disease, chronic granulomatous disease, defects or blockade of specific cytokines (particularly IL-12/IL-23/IL-17 and TNF), and HIV, is associated with suppurative foci and with primary bacteraemic disease, which may be recurrent. These patients have markedly increased mortality. Worldwide, invasive recurrent NTS bacteraemia associated with advanced HIV disease is a huge problem, and the epidemiology in this context may be more human-restricted than in other settings. This review will describe the presentation and pathogenesis of NTS in different categories of immunocompromised adults, contrasted to typhoid fever.

A user-friendly, highly sensitive assay to detect the IFN-gamma secretion by T cells

OBJECTIVES

Development of a user-friendly test alternative to ELISA-based assays to detect IFN-gamma by in vitro cultured peripheral blood mononuclear cells (PBMC) stimulated with pathogen-derived antigens.

DESIGN AND METHODS

The molecular components of an operational IFN-gamma ELISA-based test were applied in a lateral flow (LF) immuno-sandwich assay using up-converting phosphor (UCP) reporter particles. The analytical sensitivity of the UCP-LF IFN-gamma assay (ULIGA) was determined and the assay was qualitatively validated with a selection of 60 supernatants derived from PBMC cultures stimulated with M. leprae derived antigens, mitogen or medium alone.

RESULTS

ULIGA indicated an analytical sensitivity better than 2 pg/mL, and demonstrated four orders of magnitude dynamic range. The assay correlated well with the IFN-gamma ELISA.

CONCLUSIONS

ULIGA allows detection well below the cutoff value (100 pg/mL) used to define positive responses in the IFN-gamma ELISA. The test procedure is less demanding in respect to equipment and labor, and is suited for testing single samples.

Targets of anticytokine therapy and the risk of infections in humans and mice

PURPOSE OF REVIEW

To examine the type and risk of infections in humans and mice deficient in proinflammatory cytokines. Naturally occurring or manipulated genetic defects of tumor necrosis factor, interleukins-1, -6, -12, and -15, and interferon-gamma are examined for their increased susceptibility to, or protection from, infection.

RECENT FINDINGS

Interleukin-12p40 and interferon-gamma-blockers may lead to increased incidence of infections with intracellular bacteria, parasites, and fungi. In addition, we may see viral infections with interferon-gamma-blockers. Increased risk of infections is unlikely with either interleukin-1- or interleukin-15-blockers. Interleukin-6-blockers may lead to increased risk of infection with extracellular bacteria, viruses, parasites and fungi.

SUMMARY

In tumor necrosis factor knockout mice, increased susceptibility to pathogens are reported that are normally controlled by granuloma formation. In patients treated with tumor necrosis factor-blockers, a two-fold increase of granulomatous infections, predominantly reactivation of latent tuberculosis, is found. The infections detected in tumor necrosis factor knockout mice were accurate for predicting the infections observed when using tumor necrosis factor-blockers. If a similar correlation exists for other cytokines, the use of interferon-gamma and interleukin-12p40 blockers, and possibly interleukin-6 blockers, will lead to an increased risk for severe infections. Care should be taken when new cytokine blockers/antagonists are introduced.

Dectin-1 interaction with Mycobacterium tuberculosis leads to enhanced IL-12p40 production by splenic dendritic cells

Dectin-1 is a fungal pattern recognition receptor that binds to beta-glucans and triggers cytokine production by facilitating interaction with TLR2 or by directly activating spleen tyrosine kinase (Syk). To assess the possible role of Dectin-1 in the innate response to mycobacteria, we used an in vitro system in which IL-12p40 production is measured in splenic dendritic cells (SpDC) following exposure to live Mycobacterium tuberculosis bacilli. Treatment of SpDC with laminarin or glucan phosphate, two molecules known to block Dectin-1-dependent activity, led to a reduction in M. tuberculosis-induced IL-12p40 as well as IL-12p70 production. Moreover, SpDC from Dectin-1-/- chimeric mice displayed reduced IL-12p40 production in response to mycobacteria when compared with Dectin-sufficient DC. Laminarin treatment also inhibited mycobacterial-induced IL-12p40 production in DC from TLR2-/- mice, arguing that Dectin-1 functions independently of TLR2 signaling in this system. Importantly, a Dectin-1 fusion protein was found to directly bind to live mycobacteria in a laminarin-inhibitable manner indicating the presence of ligands for the receptor in the bacterium and laminarin pretreatment resulted in reduced association of mycobacteria to SpDC. In additional experiments, mycobacterial stimulation was shown to be associated with increased phosphorylation of Syk and this response was inhibited by laminarin. Furthermore, pharmacologic inhibition of Syk reduced the M. tuberculosis-induced IL-12p40 response. Together, these findings support a role for Dectin-1 in promoting M. tuberculosis-induced IL-12p40 production by DC in which the receptor augments bacterial-host cell interaction and enhances the subsequent cytokine response through an unknown mechanism involving Syk signaling.

Association of polymorphisms in IL-12/IFN-gamma pathway genes with susceptibility to pulmonary tuberculosis in Indonesia

Upon infection with mycobacteria the IL-12/IFN-gamma axis plays an essential role in the activation of cell-mediated immunity required for the elimination of pathogens. Mutations in genes of the IL-12/IFN-gamma axis are known to cause extreme susceptibility to infection with environmental mycobacteria, and subtle variations in these genes may influence susceptibility to more virulent mycobacteria. We analyzed the distribution of polymorphisms in four essential genes from the IL-12/IFN-gamma axis, IL12B, IL12RB1, IFNG and IFNGR1, in 382 pulmonary tuberculosis patients and 437 healthy controls from an endemic region in Jakarta, Indonesia. The IL12RB1 gene was sequenced in a subset of individuals. Nine known single nucleotide polymorphisms (SNPs) and two new silent variations, 135G>A and 1056C>T, were detected in IL12RB1. Six functional SNPs (-2C>T, 467G>A, 641A>G, 1312C>T, 1573G>A, 1781G>A) in IL12RB1, an IL12B promoter insertion/deletion polymorphism and CA repeats in IFNG and IFNGR1 were analyzed in the cohort. The IFNGR1 allele CA(12) (p=0.004) and genotype CA(12)/CA(12) (p=0.01; OR 0.5) were associated with protection from pulmonary tuberculosis. Interestingly, IL12B promoter heterozygosity was associated with protection from tuberculosis in BCG-vaccinated individuals (p=0.03; OR=0.6). This new finding supports the role that IL-23-of which IL12B encodes a subunit--plays in generation of memory T cells.

Pronounced susceptibility to infection by Salmonella enterica serovar Typhimurium in mice chronically exposed to lead correlates with a shift to Th2-type immune responses

Persistent exposure to inorganic lead (Pb) is known to adversely affect the immune system. In the present study, we assessed the effect of chronic Pb exposure on susceptibility to infection by the facultative intracellular pathogen Salmonella enterica serovar Typhimurium. Mice were exposed to 10 mM Pb-acetate in drinking water for approximately 16 weeks, resulting in a significant level of Pb in the blood (106.2+/-8.9 microg/dl). Pb exposure rendered mice susceptible to Salmonella infection, manifested by increased bacterial burden in target organs and heightened mortality. Flow cytometric analysis of the splenic cellular composition in normal and Pb-exposed mice revealed no gross alteration in the ratios of B and T lymphocytes or myeloid cells. Similarly, the capacity of B and T cells to upregulate the expression of activation antigens in response to mitogenic or inflammatory stimuli was not hindered by Pb exposure. Analysis of the ability of ex vivo-cultured splenocytes to secrete cytokines demonstrated a marked reduction in IFN-gamma and IL-12p40 production associated with Pb exposure. In contrast, secretion of IL-4 by splenocytes of Pb-treated mice was 3- to 3.6-fold higher than in normal mice. The increased capacity to produce IL-4 correlated with a shift in the in vivo anti-Salmonella antibody response from the protective IgG2a isotype to the Th2-induced IgG1 isotype. We conclude that chronic exposure to high levels of Pb results in a state of immunodeficiency which is not due to an overt cytotoxic or immunosuppressive mechanism, but rather is largely caused by a shift in immune responsiveness to Th2-type reactions.

Safety and immunogenicity of attenuated Salmonella enterica serovar Typhimurium delivering an HIV-1 Gag antigen via the Salmonella Type III secretion system

BACKGROUND

CKS257 (Salmonella typhimurium SL1344 DeltaphoP/phoQDelta aroA Deltaasd DeltastrA/strB pSB2131) is a live oral vaccine vector expressing HIV Gag.

METHODS

HIV Gag was expressed as a fusion protein of a Salmonella Type III secretion system protein SopE, from a balanced lethal asd-based plasmid. Eighteen healthy adults were given single escalating oral doses of 5 x 10(6) to 1 x 10(10)CFU of CKS257 and were monitored for clinical events, shedding and immune responses.

RESULTS

Adverse events were mild except at the highest dose. Volunteers shed the organism an average of 5.1 days (range 0-13 days). Eighty-three percent (15/18) of subjects had a mucosal immune response to Salmonella LPS and flagella by IgA ELISPOT assay. Seventy-two percent (13/18) of subjects seroconverted to Salmonella antigens. No volunteer had a response to recombinant Gag as measured by serology, IgA ELISPOT, or immediate ex vivo gamma-interferon ELISPOT response to Gag peptide pools. Two volunteers responded to Gag peptides by IL-2 ELISPOT, and 4 of 10 volunteers receiving >or=5 x 10(8)CFU had a response to HIV peptides in a cultured gamma-interferon ELISPOT assay.

CONCLUSIONS

Although immunogenicity of the HIV antigen needs augmentation, the attenuated Salmonella strain proved to be an excellent platform for vaccine development.