BackgroundAryl hydrocarbon receptor (AhR), a transcription factor of the bHLH/PAS family, is well characterized to regulate the biochemical and toxic effects of environmental chemicals. More recently, AhR activation has been shown to regulate the differentiation of Foxp3+ Tregs as well as Th17 cells. However, the precise mechanisms are unclear. In the current study, we investigated the effect of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a potent AhR ligand, on epigenetic regulation leading to altered Treg/Th17 differentiation, and consequent suppression of colitis.Methodology/Principal FindingsDextran sodium sulphate (DSS) administration induced acute colitis in C57BL/6 mice, as shown by significant weight loss, shortening of colon, mucosal ulceration, and increased presence of CXCR3+ T cells as well as inflammatory cytokines. Interestingly, a single dose of TCDD (25 µg/kg body weight) was able to attenuate all of the clinical and inflammatory markers of colitis. Analysis of T cells in the lamina propria (LP) and mesenteric lymph nodes (MLN), during colitis, revealed decreased presence of Tregs and increased induction of Th17 cells, which was reversed following TCDD treatment. Activation of T cells from AhR+/+ but not AhR -/- mice, in the presence of TCDD, promoted increased differentiation of Tregs while inhibiting Th17 cells. Analysis of MLN or LP cells during colitis revealed increased methylation of CpG islands of Foxp3 and demethylation of IL-17 promoters, which was reversed following TCDD treatment.Conclusions/SignificanceThese studies demonstrate for the first time that AhR activation promotes epigenetic regulation thereby influencing reciprocal differentiation of Tregs and Th17 cells, and amelioration of inflammation.

Inflammatory bowel disease is a chronic, relapsing, and tissuedestructive disease. Resveratrol (3,4,5-trihydroxy-trans-stilbene), a naturally occurring polyphenol that exhibits beneficial pleiotropic health effects, is recognized as one of the most promising natural molecules in the prevention and treatment of chronic inflammatory disease and autoimmune disorders. In the present study, we investigated the effect of resveratrol on dextran sodium sulfate (DSS)-induced colitis in mice and found that it effectively attenuated overall clinical scores as well as various pathological markers of colitis. Resveratrol reversed the colitis-associated decrease in body weight and increased levels of serum amyloid A, tumor necrosis factor-␣, interleukin (IL-6), and IL-1␤. After resveratrol treatment, the percentage of CD4 ϩ T cells in mesenteric lymph nodes (MLN) of colitis mice was restored to normal levels, and there was a decrease in these cells in the colon lamina propria (LP). Likewise, the percentages of macrophages in MLN and the LP of mice with colitis were decreased after resveratrol treatment. Resveratrol also suppressed cyclooxygenase-2 (COX-2) expression induced in DSS-exposed mice. Colitis was associated with a decrease in silent mating type information regulation-1 (SIRT1) gene expression and an increase in p-inhibitory B expression and nuclear transcription factor-B (NF-B) activation. Resveratrol treatment of mice with colitis significantly reversed these changes. This study demonstrates for the first time that SIRT1 is involved in colitis, functioning as an inverse regulator of NF-B activation and inflammation. Furthermore, our results indicate that resveratrol may protect against colitis through up-regulation of SIRT1 in immune cells in the colon.

Inflammatory bowel disease (IBD) is a chronic intestinal inflammation caused by hyperactivated effector immune cells that produce pro-inflammatory cytokines. Recent studies have shown that the cannabinoid system may play a critical role in mediating protection against intestinal inflammation. However, the effect of cannabinoid receptors induction after chronic colitis progression has not been investigated. Here, we investigate the effect of cannabinoid receptor-2 (CB2) agonist, JWH-133, after chronic colitis in IL-10−/− mice. JWH-133 effectively attenuated the overall clinical score, reversed colitis-associated pathogenesis and decrease in body weight in IL-10−/− mice. After JWH-133 treatment, the percentage of CD4+ T cells, neutrophils, mast cells, natural killer (NK1.1) cells, and activated T cells in the LP of colitis mice declined after JWH-133 treatment in the intestinal lamina propria (LP) and mesenteric lymph nodes (MLN). JWH-133 was also effective in ameliorating dextran sodium sulphate (DSS)-induced colitis. In this model, JWH-133 reduced the number and percentage of macrophages and IFN-γ expressing cells that were induced during colitis progression. Treatment with aminoalkylindole 6-iodopravadoline (AM630), a CB2 receptor antagonist, reversed the colitis protection provided by JWH-133 treatment. Also, activated T cells were found to undergo apoptosis following JWH-133 treatment both in-vivo and in-vitro. These findings suggest that JWH-133 mediates its effect through CB2 receptors, and ameliorates chronic colitis by inducing apoptosis in activated T cells, reducing the numbers of activated T cells, suppressing induction of mast cells, NK cells, and neutrophils at sites of inflammation in the LP. These results support the idea that the CB2 receptor agonists may serve as a therapeutic modality against IBD.

Antibody and T-cell reactivities to Plasmodium vivax merozoite surface protein-9 (PvMSP9) were evaluated in a cross-sectional study of individuals naturally exposed to malaria infections living in Ribeirinha, a native riverine community and in Colina, a transmigrant community, Rondonia, Brazil. The antibody responses to PvMSP9-RIRII and PvMSP9-Nt domains in Ribeirinha were higher compared with Colina and correlated with age and time of malaria exposure. IgG2 was most prevalent for PvMSP9-RII in both communities, and IgG1 was the predominant isotype for PvMSP9-Nt and PvMSP9-RIRII in Ribeirinha. IFN-γ and IL-4 predominated in Ribeirinha, while IFN-γ predominated in Colina. Variation in exposure to P. vivax likely accounts for the differences observed in cytokine and antibody levels between the two populations studied.

Summary Plasmodium vivax and P. cynomolgi produce numerous caveolae-vesicle complex (CVC) structures within the surface of the infected erythrocyte membrane. These contrast with the electron-dense knob protrusions expressed at the surface of P. falciparum infected erythrocytes. Here we investigate the 3-dimensional structure of the CVCs and the identity of a predominantly expressed 95 kDa CVC protein. Liquid chromatography - tandem mass spectrometry analysis of immunoprecipitates by monoclonal antibodies from P. cynomolgi extracts identified this protein as a member of the Plasmodium helical interspersed sub-telomeric (PHIST) superfamily with a calculated mass of 81 kDa. We named the orthologous proteins PvPHIST/CVC-8195 and PcyPHIST/CVC-8195, analyzed their structural features, including a PEXEL motif, repeated sequences and a C-terminal PHIST domain, and show that PHIST/CVC-8195 is most highly expressed in trophozoites. We generated images of CVCs in 3-D using electron tomography, and used immuno-Electron Tomography (ET) to show PHIST/CVC-8195 localizes to the cytoplasmic side of the CVC tubular extensions. Targeted gene disruptions were attempted in vivo. The pcyphist/cvc-8195 gene was not disrupted, but parasites containing episomes with the tgdhfr selection cassette were retrieved by selection with pyrimethamine. This suggests that PHIST/CVC-8195 is essential for survival of these malaria parasites.

Background Plasmodium vivax is the most geographically widespread human malaria parasite. Cohort studies in Papua New Guinea have identified a rapid onset of immunity against vivax-malaria in children living in highly endemic areas. Although numerous P. vivax merozoite antigens are targets of naturally acquired antibodies, the role of many of these antibodies in protective immunity is yet unknown.Methodology/Principal FindingsIn a cohort of children aged 1–3 years, antibodies to different regions of Merozoite Surface Protein 3α (PvMSP3α) and Merozoite Surface Protein 9 (PvMSP9) were measured and related to prospective risk of P. vivax malaria during 16 months of active follow-up. Overall, there was a low prevalence of antibodies to PvMSP3α and PvMSP9 proteins (9–65%). Antibodies to the PvMSP3α N-terminal, Block I and Block II regions increased significantly with age while antibodies to the PvMSP3α Block I and PvMSP9 N-terminal regions were positively associated with concurrent P. vivax infection. Independent of exposure (defined as the number of genetically distinct blood-stage infection acquired over time (molFOB)) and age, antibodies specific to both PvMSP3α Block II (adjusted incidence ratio (aIRR) = 0.59, p = 0.011) and PvMSP9 N-terminus (aIRR = 0.68, p = 0.035) were associated with protection against clinical P. vivax malaria. This protection was most pronounced against high-density infections. For PvMSP3α Block II, the effect was stronger with higher levels of antibodies.ConclusionsThese results indicate that PvMSP3α Block II and PvMSP9 N-terminus should be further investigated for their potential as P. vivax vaccine antigens. Controlling for molFOB assures that the observed associations are not confounded by individual differences in exposure.

Resveratrol, a naturally occurring polyphenol has received significant attention as a potent anti-inflammatory agent. Inflammatory bowel disease (IBD) is a chronic intestinal inflammation caused by hyperactivated effector immune cells that produce pro-inflammatory cytokines. Myeloid derived suppressor cells (MDSCs) are a heterogeneous population characterized by the co-expression of CD11b+ and Gr-1+ and have long been known for their immunosuppressive function. We report that resveratrol effectively attenuated overall clinical scores as well as various pathological markers of colitis in IL-10−/− mice by down regulating Th1 responses. Resveratrol lessened the colitis-associated decrease in body weight and increased levels of serum amyloid A (SAA), CXCL10 and colon TNF-α, IL-6, RANTES, IL-12 and IL-1β concentrations. After resveratrol treatment, the percentage of CXCR3 expressing T cells was decreased in the spleen, mesenteric lymph nodes (MLN), and intestinal lamina propria (LP). However, the percentage and absolute numbers of CD11b+ and Gr-1+cells in the lamina propria (LP) and spleen were increased after resveratrol treatment as compared with the vehicle treatment. Co-culture of resveratrol induced CD11b+ Gr-1+ cells with T cells, attenuated T cell proliferation, and most importantly reduced IFN-γ and GM-CSF production by LP derived T cells from vehicle treated IL-10−/− mice with chronic colitis. The current study suggests that administration of resveratrol into IL-10−/− mice induces immunosuppressive CD11b+ Gr-1+ MDSCs in the colon, which correlates with reversal of established chronic colitis, and down regulation of mucosal and systemic CXCR3+ expressing effector T cells as well as inflammatory cytokines in the colon. The induction of immunosuppressive CD11b+ Gr-1+ cells by resveratrol during colitis is unique, and suggests an as-yet-unidentified mode of anti-inflammatory action of this plant polyphenol.

BackgroundThe antibody response generated during malaria infections is of particular interest, since the production of specific IgG antibodies is required for acquisition of clinical immunity. However, variations in antibody responses could result from genetic polymorphism of the HLA class II genes. Given the increasing focus on the development of subunit vaccines, studies of the influence of class II alleles on the immune response in ethnically diverse populations is important, prior to the implementation of vaccine trials.Methods and FindingsIn this study, we evaluated the influence of HLA-DRB1* and -DQB1* allelic groups on the naturally acquired humoral response from Brazilian Amazon individuals (n = 276) against P. vivax Merozoite Surface Protein-1 (MSP-1), MSP-3α and MSP-9 recombinant proteins. Our results provide information concerning these three P. vivax antigens, relevant for their role as immunogenic surface proteins and vaccine candidates. Firstly, the studied population was heterogeneous presenting 13 HLA-DRB1* and 5 DQB1* allelic groups with a higher frequency of HLA-DRB1*04 and HLA-DQB1*03. The proteins studied were broadly immunogenic in a naturally exposed population with high frequency of IgG antibodies against PvMSP1-19 (86.7%), PvMSP-3 (77%) and PvMSP-9 (76%). Moreover, HLA-DRB1*04 and HLA-DQB1*03 alleles were associated with a higher frequency of IgG immune responses against five out of nine antigens tested, while HLA-DRB1*01 was associated with a high frequency of non-responders to repetitive regions of PvMSP-9, and the DRB1*16 allelic group with the low frequency of responders to PvMSP3 full length recombinant protein.ConclusionsHLA-DRB1*04 alleles were associated with high frequency of antibody responses to five out of nine recombinant proteins tested in Rondonia State, Brazil. These features could increase the success rate of future clinical trials based on these vaccine candidates.