Regulation of interleukin-12/interleukin-23 production and the T-helper 17 response in humans

Interleukin-23 receptor genetic polymorphisms and Crohn's disease susceptibility: a meta-analysis

OBJECTIVE

This study was designed to evaluate whether interleukin-23 receptor (IL-23R) polymorphisms were associated with Crohn's disease (CD) susceptibility.

METHODS

PubMed, MEDLINE, and Embase were searched for studies that investigated the IL-23R variants and CD risk. Meta-analysis from all eligible case-control studies was performed to assess the purported associations.

RESULTS

Our analysis found that variant minor alleles for single nucleotide polymorphisms (SNPs) rs11209026 (Arg381Gln) (P < 0.00001, OR = 0.43, 95% CI (0.37-0.50)) and rs7517847 (G/G vs. T/T, P < 0.00001, OR = 0.49, 95% CI (0.38-0.64); G/G vs. T/G + T/T, (P < 0.00001, OR = 0.56, 95% CI (0.44-0.72); T/G + G/G vs. T/T, (P < 0.00001, OR = 0.71, 95% CI (0.64-0.79) of IL-23R were inversely associated with CD risk; sensitivity analysis also indicated that Caucasian population with a variant of Arg381Gln has a decreased risk for developing CD (P < 0.00001, OR = 0.43, 95% CI (0.36-0.50)).

CONCLUSION

Our meta-analysis supports that two polymorphisms (Arg381Gln and rs7517847) within the IL-23R gene may be considered to be protective factors against developing CD. Further large case-control studies especially concerning ethnicity differences and genotype-phenotype interaction should be performed to clarify possible roles of IL-23R in CD.

Comprehensive sequence analysis of the human IL23A gene defines new variation content and high rate of evolutionary conservation

A newly described heterodimeric cytokine, interleukin-23 (IL-23) is emerging as a key player in both the innate and the adaptive T helper (Th)17 driven immune response as well as an initiator of several autoimmune diseases. The rate-limiting element of IL-23 production is believed to be driven by expression of the unique p19 subunit encoded by IL23A. We set out to perform comprehensive DNA sequencing of this previously under-studied gene in 96 individuals from two evolutionary distinct human population groups, Southern African Bantu and European. We observed a total of 33 different DNA variants within these two groups, 22 (67%) of which are currently not reported in any available database. We further demonstrate both inter-population and intra-species sequence conservation within the coding and known regulatory regions of IL23A, supporting a critical physiological role for IL-23. We conclude that IL23A may have undergone positive selection pressure directed towards conservation, suggesting that functional genetic variants within IL23A will have a significant impact on the host immune response.

Ustekinumab: lessons learned from targeting interleukin-12/23p40 in immune-mediated diseases

Interleukin (IL)-12 and IL-23 are related cytokines that have been implicated in the pathogenesis of several immune-mediated disorders. IL-12 and IL-23 are heterodimers made up of a common p40 subunit complexed to unique p35 (IL-12) or p19 (IL-23) subunits. Ustekinumab is a human monoclonal antibody that specifically binds the p40 subunit of IL-12/23. Ustekinumab prevents IL-12 and IL-23 from binding their cell surface receptor complexes, thereby blocking the T helper (Th) 1 (IL-12) and Th17 (IL-23) inflammatory pathways. Here, we discuss the preclinical and human translational data supporting a role for IL-12/23 in the pathogenesis of immune-mediated disorders, and how that rationale was challenged in the clinic during the course of the ustekinumab development program in several indications including psoriasis, psoriatic arthritis, Crohn's disease, and multiple sclerosis. We review the key efficacy and safety data in each of these immune-mediated diseases and compare and contrast the safety lessons learned from IL-12/23 genetically-deficient mice and humans in context of the overall clinical trial experience with ustekinumab.

IL-23 and IL-12p70 production by monocytes and dendritic cells in primary HIV-1 infection

IL-12 enhances protective responses against HIV replication. Its production after in vitro stimulation is defective in chronic HIV infection, but higher responses can be found. IL-23 shares the p40 chain and some properties with IL-12 and enhances Th17 responses, but its role in HIV infection is unknown. The production of IL-12 and IL-23 and the respective contribution of monocytes and myeloid conventional DC (cDCs) during primary HIV infection were determined. Sixteen patients included in the French PRIMO-ANRS Cohort without antiretroviral treatment were followed prospectively and compared with uninfected donors. Intracellular p40 expression by monocytes and cDCs, analyzed by flow cytometry, was transiently increased in monocytes and cDCs in response to LPS and more consistently, in monocytes in response to LPS + IFN-gamma. IL-23 production, measured by ELISA after PBMC stimulation, was induced by LPS in strong correlation with VLs. IL-12p70 production required the addition of IFN-gamma and was transiently increased in patients compared with controls in correlation with VLs, whereas IL-23 was increased sustainedly. Therefore, an apparent domination of IL-23 over IL-12 responses occurred throughout primary HIV infection, and a potential restoration of IL-12 responses might be expected from a treatment mimicking activated T cell signals.

Intestinal bacteria and the regulation of immune cell homeostasis

The human intestine is colonized by an estimated 100 trillion bacteria. Some of these bacteria are essential for normal physiology, whereas others have been implicated in the pathogenesis of multiple inflammatory diseases including IBD and asthma. This review examines the influence of signals from intestinal bacteria on the homeostasis of the mammalian immune system in the context of health and disease. We review the bacterial composition of the mammalian intestine, known bacterial-derived immunoregulatory molecules, and the mammalian innate immune receptors that recognize them. We discuss the influence of bacterial-derived signals on immune cell function and the mechanisms by which these signals modulate the development and progression of inflammatory disease. We conclude with an examination of successes and future challenges in using bacterial communities or their products in the prevention or treatment of human disease.

The role of TLRs, NLRs, and RLRs in mucosal innate immunity and homeostasis

The mucosal surfaces of the gastrointestinal tract are continually exposed to an enormous antigenic load of microbial and dietary origin, yet homeostasis is maintained. Pattern recognition molecules (PRMs) have a key role in maintaining the integrity of the epithelial barrier and in promoting maturation of the mucosal immune system. Commensal bacteria modulate the expression of a broad range of genes involved in maintaining epithelial integrity, inflammatory responses, and production of antimicrobial peptides. Mice deficient in PRMs can develop intestinal inflammation, which is dependent on the microbiota, and in humans, PRM polymorphisms are associated with exacerbated inflammatory bowel disease. Innate immune responses and epithelial barrier function are regulated by PRM-induced signaling at multiple levels, from the selective expression of receptors on mucosal cells or compartments to the expression of negative regulators. Here, we describe recent advances in our understanding of innate signaling pathways, particularly by Toll-like receptors and nucleotide-binding domain and leucine-rich repeat containing receptors at mucosal surfaces.

How might infant and paediatric immune responses influence malaria vaccine efficacy?

Naturally acquired immunity to malaria requires repeat infections yet does not engender sterile immunity or long-lasting protective immunologic memory. This renders infants and young children the most susceptible to malaria-induced morbidity and mortality, and the ultimate target for a malaria vaccine. The prevailing paradigm is that infants initially garner protection due to transplacentally transferred anti-malarial antibodies and other intrinsic factors such as foetal haemoglobin. As these wane infants have an insufficient immune repertoire to prevent genetically diverse Plasmodium infections and an inability to control malaria-induced immunopathology. This Review discusses humoral, cell-mediated and innate immune responses to malaria and how each contributes to protection – focusing on how deficiencies in infant and paediatric immune responses might influence malaria vaccine efficacy in this population. In addition, burgeoning evidence suggests a role for inhibitory receptors that limit immunopathology and guide the development of long-lived immunity. Precisely how age or malaria infections influence the function of these regulators is unknown. Therefore the possibility that infants may not have the immune-dexterity to balance effective parasite clearance with timely immune-regulation leading to protective immunologic memory is considered. And thus, malaria vaccines tested in adults and older children may not be predictive for trials conducted in infants.

Encephalitogenicity of complete Freund's adjuvant relative to CpG is linked to induction of Th17 cells

For decades, CFA has been the classic adjuvant for the induction of experimental autoimmune encephalomyelitis (EAE). Its encephalitogenic activity has been originally linked to the induction of Th1 responses. CpG, which is also a potent Th1 inducer, has been suggested by some studies to be comparably encephalitogenic. In this study, using the SJL proteolipid protein (PLP) 139-151 peptide EAE model, we show that active immunizations using CFA but not CpG 1826/IFA as an adjuvant induced disease. Passive induction of EAE resulted in severe disease when cells were transferred from PLP in CFA-primed mice but resulted in only a mild, transient disease when cells originated from PLP in CpG 1826/IFA-primed mice. In accordance with these findings, immunizations using CFA but not CpG 1826/IFA as an adjuvant elicited a delayed-type hypersensitivity response. ELISPOT analysis revealed that CFA promoted the differentiation of much higher levels of PLP-specific, IL-17-secreting cells compared with CpG 1826/IFA. Both adjuvants induced comparable frequencies of PLP-specific, IFN-gamma-secreting cells and also induced Ag-specific proliferation to the same extent. The severity of EAE in PLP in CFA-immunized mice was reduced when IL-17 was neutralized in vivo, demonstrating the crucial role of this cytokine in disease induction. The data show that immunizations using the autoantigen in CpG 1826/IFA result in very low frequencies of Ag-specific IL-17 cells, suggesting a lower risk of Th17-mediated pathology when using this adjuvant.

Modulation of adaptive immunity with Toll-like receptors

The discovery of Toll-like receptors (TLRs), and their role in sensing infections represents one of the most seminal advances in immunology in recent years. It is now clear that TLRs play a fundamental role in innate recognition of microbes, and stimulate and tune the quality of the adaptive immune response. However, major knowledge gaps remain in our understanding of how TLRs regulate the development and persistence of T- and B-cell memory. Here, we review our current understanding of how TLR-signaling shapes the adaptive immune response, and highlight unanswered questions, the solution of which will be imperative in the rational exploitation of TLRs in vaccine design and immune therapy.

Microarray analysis of lymphatic tissue reveals stage-specific, gene expression signatures in HIV-1 infection

Untreated HIV-1 infection progresses through acute and asymptomatic stages to AIDS. Although each of the three stages has well-known clinical, virologic, and immunologic characteristics, much less is known of the molecular mechanisms underlying each stage. In this study, we report lymphatic tissue microarray analyses, revealing for the first time stage-specific patterns of gene expression during HIV-1 infection. We show that although there is a common set of key genes with altered expression throughout all stages, each stage has a unique gene expression signature. The acute stage is most notably characterized by increased expression of hundreds of genes involved in immune activation, innate immune defenses (e.g., RIG-1, MDA-5, TLR7 and TLR8, PKR, APOBEC3B, 3F, 3G), adaptive immunity, and in the proapoptotic Fas-Fas ligand pathway. Yet, quite strikingly, the expression of nearly all acute stage genes return to baseline levels in the asymptomatic stage, accompanying partial control of infection. This transition from acute to asymptomatic stage is tied to increased expression of a diverse array of immunosuppressive genes (e.g., CLEC12B, ILT4, galectin-3, CD160, BCMA, FGL2, LAG3, GPNMB). In the AIDS stage, decreased expression of numerous genes involved in T cell signaling identifies genes contributing to T cell dysfunction. These common and stage-specific gene expression signatures identify potential molecular mechanisms underlying the host response and the slow, natural course of HIV-1 infection.

Cathepsin X prevents an effective immune response against Helicobacter pylori infection

Cathepsin X, a cysteine protease, has been shown to regulate an immune response by activating beta-2 integrin receptors. In this study we demonstrate its role in regulating the immune response to infection with H. pylori. The level of cathepsin X was determined in THP-1 monocyte cells primed with H. pylori antigens isolated from subjects suffering from gastritis, who had either eradicated or not the disease after the antibiotic therapy. We show that the specific clinical outcome of H. pylori eradication therapy correlates strongly with the membrane expression of cathepsin X in stimulated THP-1 cells, being significantly higher after stimulation with H. pylori strains from those subjects who did not respond to antibiotic therapy. The same antigens elicit a more vigorous immune response, increased expression of MHC II, however trigger inadequate cytokine profile (IFN-gamma and IL-4) to eradicate the pathogen. We propose that cathepsin X mediated activation of beta-2 integrin receptor Mac-1 suppresses the stimulatory signal in the form of cytokines. Cathepsin X co-localizes on the membrane of THP-1 cells with Mac-1 integrin receptor and its inhibition increases homotypic aggregation and mononuclear cell proliferation, events that are associated with low Mac-1 activity. Our study highlights the diversity of the innate immune response to H. pylori antigens leading to either successful eradication of the infection or maintenance of chronic inflammation, revealing cathepsin X location and activity as a regulator of the effectiveness of H. pylori eradication.

Neutralization of interleukin-10 from CD14(+) monocytes enhances gamma interferon production in peripheral blood mononuclear cells from Mycobacterium avium subsp. paratuberculosis-infected goats

The gamma interferon assay is used to identify Mycobacterium avium subsp. paratuberculosis-infected animals. It has been suggested that regulatory mechanisms could influence the sensitivity of the test when it is performed with cells from cattle and that the neutralization of interleukin-10 (IL-10) in vitro would increase the gamma interferon responses. To investigate the regulatory mechanisms affecting the gamma interferon assay with cells from goats, blood was collected from M. avium subsp. paratuberculosis-infected, M. avium subsp. paratuberculosis-exposed, and noninfected goats. Neutralization of IL-10 by a monoclonal antibody resulted in increased levels of gamma interferon production in M. avium subsp. paratuberculosis purified protein derivative (PPDj)-stimulated samples from both infected and exposed goats. However, the levels of gamma interferon release were also increased in unstimulated cells and in PPDj-stimulated cells from some noninfected animals following neutralization. Depletion of putative regulatory CD25(high) T cells had no clear effect on the number of gamma-interferon-producing cells. The IL-10-producing cells were identified to be mainly CD14(+) major histocompatibility complex class II-positive monocytes in both PPDj-stimulated and control cultures and not regulatory T cells. However, possible regulatory CD4(+) CD25(+) T cells produced IL-10 in response to concanavalin A stimulation. The numbers of CD4(+), CD8(+), and CD8(+) gammadelta T-cell receptor-positive cells producing gamma interferon increased following IL-10 neutralization. These results provide insight into the source and the role of IL-10 in gamma interferon assays with cells from goats and suggest that IL-10 from monocytes can regulate both innate and adaptive gamma interferon production from several cell types. Although IL-10 neutralization increased the sensitivity of the gamma interferon assay, the specificity of the test could be compromised.

Ex vivo generation of mature equine monocyte-derived dendritic cells

Dendritic cells (DCs) are innate immune cells specialized in antigen detection and presentation. They perform an essential role in initiating and guiding the immune response, the direction of which largely depends upon the activation state of the DCs. The objective of this study was to generate mature equine monocyte-derived DCs and, in doing so, to develop a method for measuring the activation state of these cells. Equine DCs were stimulated with UV-inactivated Escherichia coli (E. coli), and the activation status was measured by analyzing cell surface marker expression, cytokine production, and endocytic capacity. Comparisons for each parameter measured were performed between macrophages, non-stimulated DCs and stimulated DCs. Equine monocyte-derived DCs may be distinguished from macrophages based on cell surface expression of MHC class II (p<0.0001) and CD206 (p<0.0001), their capacity for endocytosis of FITC-dextran (p<0.05), and production of TNF-alpha upon stimulation (p<0.001). Furthermore, stimulated DCs can be distinguished from non-stimulated DCs based on increased cell surface expression of MHC class II (p<0.0001) and upregulation of pro-inflammatory cytokine mRNA, particularly IL-12/IL-23p40 (p<0.05) and IL-23p19 (p<0.05). The ability to measure DC activation state will facilitate future investigations of equine DC function.