Induction of CD4+CD25+FOXP3+ Regulatory T Cells during Human Hookworm Infection Modulates Antigen-Mediated Lymphocyte Proliferation

Hookworm infection is considered one of the most important poverty-promoting neglected tropical diseases, infecting 576 to 740 million people worldwide, especially in the tropics and subtropics. These blood-feeding nematodes have a remarkable ability to downmodulate the host immune response, protecting themselves from elimination and minimizing severe host pathology. While several mechanisms may be involved in the immunomodulation by parasitic infection, experimental evidences have pointed toward the possible involvement of regulatory T cells (Tregs) in downregulating effector T-cell responses upon chronic infection. However, the role of Tregs cells in human hookworm infection is still poorly understood and has not been addressed yet. In the current study we observed an augmentation of circulating CD4+CD25+FOXP3+ regulatory T cells in hookworm-infected individuals compared with healthy non-infected donors. We have also demonstrated that infected individuals present higher levels of circulating Treg cells expressing CTLA-4, GITR, IL-10, TGF-β and IL-17. Moreover, we showed that hookworm crude antigen stimulation reduces the number of CD4+CD25+FOXP3+ T regulatory cells co-expressing IL-17 in infected individuals. Finally, PBMCs from infected individuals pulsed with excreted/secreted products or hookworm crude antigens presented an impaired cellular proliferation, which was partially augmented by the depletion of Treg cells. Our results suggest that Treg cells may play an important role in hookworm-induced immunosuppression, contributing to the longevity of hookworm survival in infected people

Centrality evolution of the charged-particle pseudorapidity density over a broad pseudorapidity range in Pb-Pb collisions at root s(NN)=2.76TeV

Peer reviewe

Schistosome syntenin partially protects vaccinated mice against Schistosoma mansoni infection.

Schistosomiasis is a neglected tropical disease caused by several species of trematode of the genus Schistosoma. The disease affects more than 200 million people in the world and causes up to 280,000 deaths per year, besides having high morbidity due to chronic illness that damages internal organs. Current schistosomiasis control strategies are mainly based on chemotherapy, but many researchers believe that the best long-term strategy to control disease is a combination of drug treatment and immunization with an anti-schistosome vaccine. Among the most promising molecules as vaccine candidates are the proteins present in the tegument and digestive tract of the parasite.In this study, we describe for the first time Schistosoma mansoni syntenin (SmSynt) and we evaluate its potential as a recombinant vaccine. We demonstrate by real-time PCR that syntenin is mainly expressed in intravascular life stages (schistosomula and adult worms) of the parasite life cycle and, by confocal microscopy, we localize it in digestive epithelia in adult worms and schistosomula. Administration of siRNAs targeting SmSynt leads to the knock-down of syntenin gene and protein levels, but this has no demonstrable impact on parasite morphology or viability, suggesting that high SmSynt gene expression is not essential for the parasites in vitro. Mice immunization with rSmSynt, formulated with Freund's adjuvant, induces a Th1-type response, as suggested by the production of IFN-γ and TNF-α by rSmSynt-stimulated cultured splenocytes. The protective effect conferred by vaccination with rSmSynt was demonstrated by 30-37% reduction of worm burden, 38-43% reduction in the number, and 35-37% reduction in the area, of liver granulomas.Our report is the first characterization of syntenin in Schistosoma mansoni and our data suggest that this protein is a potential candidate for the development of a multi-antigen vaccine to control schistosomiasis

<i>Sm</i>10.3, a Member of the Micro-Exon Gene 4 (MEG-4) Family, Induces Erythrocyte Agglutination <i>In Vitro</i> and Partially Protects Vaccinated Mice against <i>Schistosoma mansoni</i> Infection

<div><p>Background</p><p>The parasitic flatworm <i>Schistosoma mansoni</i> is a blood fluke that causes schistosomiasis. Current schistosomiasis control strategies are mainly based on chemotherapy, but many researchers believe that the best long-term strategy to control disease is a combination of drug treatment and immunization with an anti-schistosome vaccine. Numerous antigens that are expressed at the interface between the parasite and the mammalian host have been assessed. Among the most promising molecules are the proteins present in the tegument and digestive tract of the parasite.</p><p>Methodology/Principal Findings</p><p>In this study, we evaluated the potential of <i>Sm</i>10.3, a member of the micro-exon gene 4 (MEG-4) family, for use as part of a recombinant vaccine. We confirmed by real-time PCR that <i>Sm10.3</i> was expressed at all stages of the parasite life cycle. The localization of <i>Sm</i>10.3 on the surface and lumen of the esophageal and intestinal tract in adult worms and lung-stage schistosomula was confirmed by confocal microscopy. We also show preliminary evidence that r<i>Sm</i>10.3 induces erythrocyte agglutination <i>in vitro</i>. Immunization of mice with r<i>Sm</i>10.3 induced a mixed Th1/Th2-type response, as IFN-γ, TNF-α, and low levels of IL-5 were detected in the supernatant of cultured splenocytes. The protective effect conferred by vaccination with r<i>Sm</i>10.3 was demonstrated by 25.5–32% reduction in the worm burden, 32.9–43.6% reduction in the number of eggs per gram of hepatic tissue, a 23.8% reduction in the number of granulomas, an 11.8% reduction in the area of the granulomas and a 39.8% reduction in granuloma fibrosis.</p><p>Conclusions/Significance</p><p>Our data suggest that <i>Sm</i>10.3 is a potential candidate for use in developing a multi-antigen vaccine to control schistosomiasis and provide the first evidence for a possible role for <i>Sm</i>10.3 in the blood feeding process.</p></div

Cytokine profile of splenocytes recovered from r<i>Sm</i>Synt-vaccinated versus control mice.

<p>Ten days after the final immunization with r<i>Sm</i>Synt or PBS, splenocytes from five mice were isolated and assayed for their IFN-γ (<b>A</b>), TNF-α (<b>B</b>) and IL-10 (<b>C</b>) production (mean +/− SD) in response to stimulation with r<i>Sm</i>Synt (25 µg, middle group) or ConA/LPS (right group) or medium (left group). The cytokine profile was also evaluated after the challenge with cercariae where high levels of IFN-γ (<b>D</b>), TNF-α (<b>E</b>) and IL-10 (<b>F</b>) were detected as well. Significant differences between data from mice immunized with r<i>Sm</i>Synt and the PBS-control group are denoted by *, p<0.05 or ***, p<0.001.</p

Histological analysis of hepatic tissue from mice vaccinated with r<i>Sm</i>10.3.

<p>The r<i>Sm</i>10.3-vaccinated and control animals from the first vaccination trial were sacrificed, and their livers were washed with PBS and stored in formaldehyde until sectioning and staining with picrosirius. (A) A representative sample from the PBS control group. (C) A representative sample from a mouse vaccinated with r<i>Sm</i>10.3. (B and D) Images were edited using image software to highlight the fibrotic areas in red. The images were captured using a 40× objective lens. (E), Graph showing a 23.8% reduction in the number of granulomas in vaccinated mice. (F), Graph showing a 11.8% reduction in the granuloma area in vaccinated mice. (G), Graph showing a 39.8% reduction in the granuloma fibrosis in vaccinated mice. Twenty granulomas with a single-well-defined egg were randomly selected in each liver section for the granuloma analysis. Error bars indicate intra-assay standard deviation of means. Asterisks indicate statistically significant differences between the vaccinated groups and the control group (<i>p</i><0.05).</p

Immunolocalization of <i>Sm</i>10.3 in <i>S. mansoni</i> adult worms and lung-stage schistosomula.

<p>Mouse polyclonal anti-r<i>Sm</i>10.3 and anti-mouse secondary antibodies coupled to Alexa 488 (green) were used to label the native <i>Sm</i>10.3 protein (C, D, G, H, K, L). Serum from naive mice was used as a negative control (A, B, E, F, I, J). Nuclei were stained with DAPI (blue), and actin was stained with phalloidin conjugated to rhodamine (red). White arrows indicate the localization of <i>Sm</i>10.3 in the internal tissues of the schistosomula and on the surface and lumen of the esophageal and intestinal tegument of adult worms. Schistosomula are shown as maximum Z projections of 3 planes imaged with 1.0 µm distance intervals and adult parasites are single scans.</p