Harnessing the Therapeutic Potential of Th17 Cells

Th17 cells provide protective immunity to infections by fungi and extracellular bacteria as well as cancer but are also involved in chronic inflammation. The cells were first identified by their ability to produce interleukin 17A (IL-17A) and, subsequently, associated with chronic inflammation and autoimmunity. Th17 cells have some gene profile similarity with stem cells and can remain dormant in mucosal tissues for long periods. Indeed, recent studies suggest that functionally distinct subsets of pro- and anti-inflammatory Th17 cells can interchange phenotype and functions. For development, Th17 cells require activation of the transcription factors STAT3 and RORγt while RUNX1, c-Maf, and Aiolos are involved in changes of phenotype/functions. Attempts to harness Th17 cells against pathogens and cancer using vaccination strategies are being explored. The cells gain protective abilities when induced to produce interferon γ (IFNγ). In addition, treatment with antibodies to IL-17 is effective in treating patients with psoriasis, psoriatic arthritis, and refectory rheumatoid arthritis. Moreover, since RORγt is a nuclear receptor, it is likely to be a potential future drug target for modulating Th17 functions. This review explores pathways through which Th17 subsets are induced, the molecular basis of their plasticity, and potential therapeutic strategies for their modulation in diseases

Methionine Sulfoxide Reductase A (MsrA) Deficient Mycoplasma genitalium Shows Decreased Interactions with Host Cells

Mycoplasma genitalium is an important sexually transmitted pathogen that affects both men and women. In genital-mucosal tissues, it initiates colonization of epithelial cells by attaching itself to host cells via several identified bacterial ligands and host cell surface receptors. We have previously shown that a mutant form of M. genitalium lacking methionine sulfoxide reductase A (MsrA), an antioxidant enzyme which converts oxidized methionine (Met(O)) into methionine (Met), shows decreased viability in infected animals. To gain more insights into the mechanisms by which MsrA controls M. genitalium virulence, we compared the wild-type M. genitalium strain (G37) with an msrA mutant (MS5) strain for their ability to interact with target cervical epithelial cell lines (HeLa and C33A) and THP-1 monocytic cells. Infection of epithelial cell lines with both strains revealed that MS5 was less cytotoxic to HeLa and C33A cell lines than the G37 strain. Also, the MS5 strain was more susceptible to phagocytosis by THP-1 cells than wild type strain (G37). Further, MS5 was less able to induce aggregation and differentiation in THP-1 cells than the wild type strain, as determined by carboxyfluorescein diacetate succinimidyl ester (CFSE) labeling of the cells, followed by counting of cells attached to the culture dish using image analysis. Finally, MS5 was observed to induce less proinflammatory cytokine TNF-α by THP-1 cells than wild type G37 strain. These results indicate that MsrA affects the virulence properties of M. genitalium by modulating its interaction with host cells

High-affinity Fc receptor expression indicates relative immaturity in human monocytes

Within monocyte heterogeneity, subsets represent discrete, well-characterised phenotypes. Although many studies have highlighted differences between subsets, there is evidence that subpopulations represent contiguous stages in a maturational series. As CD14hiCD64hi monocytes have higher proliferative potential than CD14hiCD64lomonocytes, the surface marker profile on four subsets defined by CD14 and CD64 was measured. The profiles were compared to that of subsets defined by the high affinity IgE receptor (FcεRIα), CD16 and CD14; further differences in size, granularity and buoyancy were measured in subsets delineated by these markers. There was a positive correlation between proliferative monocyte (PM) prevalence and CD64 expression on the ‘classical’ monocyte subset, and also between PM prevalence and circulating FcεRIα+monocytes. The expression of CD64, the high affinity IgG receptor, on canonical human monocyte subsets was determined before and aftershorttermculture, and in responseto IL-6, IL-10, M-CSF, GM-CSF and IFNγ;the influence of these cytokines on monocyte subset transition was also measured. The loss of FcεRIαexpression preceded an increasein CD16 expression in wholeblood cultures. These data indicate high affinity Fc receptors are expressed on less mature monocytes and that FcεRIα+ monocytes are developmentally antecedent to the canonical classical and intermediate monocyte subsets

Ibudilast inhibits chemokine expression in rheumatoid synovial fibroblasts and exhibits immunomodulatory activity in experimental arthritis

Objective: Ibudilast is a well‐tolerated, orally available type 4 phosphodiesterase (PDE4) inhibitor used to treat asthma and stroke. As PDE4 inhibition suppresses inflammatory mediator production and cell proliferation in leukocytes, ibudilast may be a valuable therapy for the treatment of inflammatory auto‐immune diseases such as rheumatoid arthritis (RA). We assessed the therapeutic potential of ibudilast by measuring its capacity to modulate inflammation in human leukocytes, RA synovial fibroblasts (RASF) and in experimental arthritis.Methods: Using standard curve‐qPCR, the effect of ibudilast on gene expression in activated human leukocytes and RASF was measured. Ibudilast was used to treat DBA/1 mice with collagen‐induced arthritis and an adoptive transfer model was used to assess its tolerogenic capacity.Results: Ibudilast inhibited the expression of TNF, IL12A and IL12B, the secretion of TNFα and IL12/23p40 from leukocytes and reduced the expression of CCL5 and CCL3 in activated RASF. Treatment of experimental arthritis with ibudilast resulted in a reduction in IL‐17‐producing cells and inhibition of disease progression. When combined with a TNF‐inhibitor, ibudilast caused marked suppression of active disease. Exposure of leukocytes from type II collagen‐immunised DBA/1 mice to ibudilast in vitro attenuated their ability to adoptively‐transfer arthritis to DBA/1J‐PrkdcSCID mice, providing evidence of an immunomodulatory effect.Conclusion: Ibudilast reduced the expression and/or secretion of inflammatory mediators from activated human leukocytes and RASF, inhibited Th17 responses in vivo and improved established arthritis. Given the established safety profile of ibudilast in man, its clinical evaluation in RA, either alone or in combination with a TNF inhibitor, should be considered

Ibudilast inhibits chemokine expression in rheumatoid synovial fibroblasts and exhibits immunomodulatory activity in experimental arthritis

Objective: Ibudilast is a well‐tolerated, orally available type 4 phosphodiesterase (PDE4) inhibitor used to treat asthma and stroke. As PDE4 inhibition suppresses inflammatory mediator production and cell proliferation in leukocytes, ibudilast may be a valuable therapy for the treatment of inflammatory auto‐immune diseases such as rheumatoid arthritis (RA). We assessed the therapeutic potential of ibudilast by measuring its capacity to modulate inflammation in human leukocytes, RA synovial fibroblasts (RASF) and in experimental arthritis.Methods: Using standard curve‐qPCR, the effect of ibudilast on gene expression in activated human leukocytes and RASF was measured. Ibudilast was used to treat DBA/1 mice with collagen‐induced arthritis and an adoptive transfer model was used to assess its tolerogenic capacity.Results: Ibudilast inhibited the expression of TNF, IL12A and IL12B, the secretion of TNFα and IL12/23p40 from leukocytes and reduced the expression of CCL5 and CCL3 in activated RASF. Treatment of experimental arthritis with ibudilast resulted in a reduction in IL‐17‐producing cells and inhibition of disease progression. When combined with a TNF‐inhibitor, ibudilast caused marked suppression of active disease. Exposure of leukocytes from type II collagen‐immunised DBA/1 mice to ibudilast in vitro attenuated their ability to adoptively‐transfer arthritis to DBA/1J‐PrkdcSCID mice, providing evidence of an immunomodulatory effect.Conclusion: Ibudilast reduced the expression and/or secretion of inflammatory mediators from activated human leukocytes and RASF, inhibited Th17 responses in vivo and improved established arthritis. Given the established safety profile of ibudilast in man, its clinical evaluation in RA, either alone or in combination with a TNF inhibitor, should be considered.</br

Plasmid DNA as a safe gene delivery vehicle for treatment of chronic inflammatory disease.

BACKGROUND: The development of plasmid DNA (pDNA) vectors for safe and efficacious gene transfer therapy for chronic inflammatory diseases is a natural sequel to biological therapies which, whilst effective, are relatively expensive, require frequent administration and are not suitable for all patients. OBJECTIVE: To outline the methods of non-viral gene therapy using pDNA and detail research on potential targets in the treatment of chronic inflammatory diseases, with particular emphasis on multiple sclerosis, rheumatoid arthritis and osteoarthritis. METHODS: A comprehensive online journal search was used to examine current approaches in pDNA transfer and practical applications in chronic inflammatory diseases; conditions with similar disease processes were also considered. RESULTS/CONCLUSION: Significant progress has been made in increasing the efficiency and efficacy of non-viral gene transfer. For modulation of inflammatory targets, the conversion of biological therapy to gene therapy using pDNA is achievable

Lymphocytes: precursor frequencies

The frequency of antigen‐specific cells will vary during development and in response to the first and subsequent encounters with an antigen, either through infection or immunisation, and is an important indicator of adaptive immune function. Antigen‐specific lymphocyte prevalence can be estimated indirectly and directly using several different techniques. Functional assays have been used for several decades to indirectly calculate the frequency of antigen‐specific lymphocytes by measuring a proliferative response, cytokine production or cytolytic activity in response to antigenic stimulation. The functional activity of individual lymphocytes is also able to be measured directly, which allows phenotypic analyses of antigen‐specific cells. More recently, labelled MHC (major histocompatibility complex)/peptide multimers have allowed researchers to directly enumerate and comprehensively phenotype lymphocytes using multiparameter flow cytometry

Lymphocytes: precursor frequencies

The frequency of antigen‐specific cells will vary during development and in response to the first and subsequent encounters with an antigen, either through infection or immunisation, and is an important indicator of adaptive immune function. Antigen‐specific lymphocyte prevalence can be estimated indirectly and directly using several different techniques. Functional assays have been used for several decades to indirectly calculate the frequency of antigen‐specific lymphocytes by measuring a proliferative response, cytokine production or cytolytic activity in response to antigenic stimulation. The functional activity of individual lymphocytes is also able to be measured directly, which allows phenotypic analyses of antigen‐specific cells. More recently, labelled MHC (major histocompatibility complex)/peptide multimers have allowed researchers to directly enumerate and comprehensively phenotype lymphocytes using multiparameter flow cytometry

IDO and kunurenine metabolites in peripheral and CNS disorders

The importance of the kynurenine pathway in normal immune system function has led to an appreciation of its possible contribution to autoimmune disorders such as rheumatoid arthritis. Indoleamine-2,3-dioxygenase (IDO) activity exerts a protective function, limiting the severity of experimental arthritis, whereas deletion or inhibition exacerbates the symptoms. Other chronic disorder with an inflammatory component, such as atherosclerosis, are also suppressed by IDO activity. It is suggested that this overall anti-inflammatory activity is mediated by a change in the relative production or activity of Th17 and regulatory T cell populations. Kynurenines may play an anti-inflammatory role also in CNS disorders such as Huntington's disease, Alzheimer's disease and multiple sclerosis, in which signs of inflammation and neurodegeneration are involved. The possibility is discussed that in Huntington's disease kynurenines interact with other anti-inflammatory molecules such as Human Lymphocyte Antigen-G which may be relevant in other disorders. Kynurenine involvement may account for the protection afforded to animals with cerebral malaria and trypanosomiasis when they are treated with an inhibitor of kynurenine-3-monoxygenase (KMO). There is some evidence that changes in IL-10 may contribute to this protection and the relationship between kynurenines and IL-10 in arthritis and other inflammatory conditions should be explored. In addition, metabolites of kynurenine downstream of KMO, such as anthranilic acid and 3-hydroxy-anthranilic acid can influence inflammation, and the ratio of these compounds is a valuable biomarker of inflammatory status although the underlying molecular mechanisms of the changes require clarification. Hence it is essential that more effort be expended to identify their sites of action as potential targets for drug development. Finally, we discuss increasing awareness of the epigenetic regulation of IDO, for example by DNA methylation, a phenomenon which may explain differences between individuals in their susceptibility to arthritis and other inflammatory disorders