The effects of nitric oxide on the immune system during Trypanosoma cruzi infection

Trypanosoma cruzi infection triggers substantial production of nitric oxide (NO), which has been shown to have protective and toxic effects on the host's immune system. Sensing of trypomastigotes by phagocytes activates the inducible NO-synthase (NOS2) pathway, which produces NO and is largely responsible for macrophage-mediated killing of T. cruzi. NO is also responsible for modulating virtually all steps of innate and adaptive immunity. However, NO can also cause oxidative stress, which is especially damaging to the host due to increased tissue damage. The cytokines IFN-³ and TNF-±, as well as chemokines, are strong inducers of NOS2 and are produced in large amounts during T. cruzi acute infection. Conversely, TGF-² and IL-10 negatively regulate NO production. Here we discuss the recent evidence describing the mechanisms by which NO is able to exert its antimicrobial and immune regulatory effects, the mechanisms involved in the oxidative stress response during infection and the implications of NO for the development of therapeutic strategies against T. cruzi.FAPESPFRSGTWPMPMMGThe Millennium Institute for Vaccine Development and TechnologyCNP

SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts

Abstract\ud \ud \ud \ud Background\ud \ud Toxoplasma gondii is an intracellular parasite that causes relevant clinical disease in humans and animals. Several studies have been performed in order to understand the interactions between proteins of the parasite and host cells. SAG2A is a 22 kDa protein that is mainly found in the surface of tachyzoites. In the present work, our aim was to correlate the predicted three-dimensional structure of this protein with the immune system of infected hosts.\ud \ud \ud \ud Methods\ud To accomplish our goals, we performed in silico analysis of the amino acid sequence of SAG2A, correlating the predictions with in vitro stimulation of antigen presenting cells and serological assays.\ud \ud \ud \ud Results\ud Structure modeling predicts that SAG2A protein possesses an unfolded C-terminal end, which varies its conformation within distinct strain types of T. gondii. This structure within the protein shelters a known B-cell immunodominant epitope, which presents low identity with its closest phyllogenetically related protein, an orthologue predicted in Neospora caninum. In agreement with the in silico observations, sera of known T. gondii infected mice and goats recognized recombinant SAG2A, whereas no serological cross-reactivity was observed with samples from N. caninum animals. Additionally, the C-terminal end of the protein was able to down-modulate pro-inflammatory responses of activated macrophages and dendritic cells.\ud \ud \ud \ud Conclusions\ud Altogether, we demonstrate herein that recombinant SAG2A protein from T. gondii is immunologically relevant in the host-parasite interface and may be targeted in therapeutic and diagnostic procedures designed against the infection.The authors thank Marley Dantas Barbosa and Zilda Mendonça da Silva Rodrigues for technical assistance. This work was supported by Brazilian funding agencies CNPq, CAPES and FAPEMIG.The authors thank Marley Dantas Barbosa and Zilda Mendonça da Silva Rodrigues for technical assistance. This work was supported by Brazilian funding agencies CNPq, CAPES and FAPEMIG

Aerobic and resistance exercises interfere in anti-Toxoplasma gondii antibody profile of pre-training C57Bl/6 mice in a model of experimental toxoplasmosis.

Regular physical exercise has been implicated to improve general human health and to decrease susceptibility against many diseases, including those triggered by protozoan parasites. The aim of this work was to investigate whether pre-training could improve the susceptibility to Toxoplasma gondii by determining the antibody profile from IgM, IgGtotal, IgG1 and IgG2a isotypes produced by C57Bl/6 mice. A total of 30 male (23.7±1.09g) were used for this study. The animals were allocated in five groups (6 per group), as follows: i) non infected sedentary (NIS), ii) infected sedentary (IS), iii) non-infected exercised (NIEx), iv) infected exercised (IEx), v) infected exercised that stopped after 30 days infection (IEx+30). The animals were housed in an animal facility with a 12 h light/dark cycle (the lights were switched off at 7:00 a.m.) maintained at controlled temperature (22-24°C) with food and water provided ad libitum. The 6 week-old mice started exercising (NIEx, IEx and IEx+30) and two groups (NIEx and IEx) stopped 6.5 weeks later, then three groups were infected (IS, IEx and IEx+30) with 5 cists of T. gondii and 30 days later all five groups were euthanatized and blood was collected. We found no significant differences among all groups and negative control. We did a similar 5 cists infection in 6 week-old C57Bl/6 mice and we found a significant different using ELISA index among infected to non-infected and negative control. These data suggest that it is possible to increase the amount of cists when infection is carried out in older mice. In addition, we could observe that 50% of mice from the IEx+30 group and 16.7% from IEx presented up to 50% of IgG2a ELISA index when compared to all other groups of animal. As IgG2a is a characteristic antibody isotype induced by Th1 immune response in murine model, the most significant mechanism to control T. gondii infection, it can be concluded that the exercise it is important to improve protective immune response in this model, when compared to sedentary infected animals

Lectins from Synadenium carinatum (ScLL) and Artocarpus heterophyllus (ArtinM) are able to induce beneficial immunomodulatory effects in a murine model for treatment of Toxoplasma gondii infection

Infection by Toxoplasma gondii affects around one-third of world population and the treatment for patients presenting toxoplasmosis clinically manifested disease is mainly based by a combination of sulfadiazine, pyrimethamine and folinic acid. However, this therapeutic protocol is significantly toxic, causing relevant dose-related bone marrow damage. Thus, it is necessary to improve new approaches to investigate the usefulness of more effective and non-toxic agents for treatment of patients with toxoplasmosis. It has been described that lectins from plants can control parasite infections, when used as immunological adjuvants in vaccination procedures. This type of lectins, such as ArtinM and ScLL is able to induce immunostimulatory activities, including efficient immune response against parasites. The present study aimed to evaluate the potential immunostimulatory effect of ScLL and ArtinM for treatment of T. gondii infection during acute phase, considering that there is no study in the literature accomplishing this issue. For this purpose, bone marrow-derived macrophages (BMDMs) were treated with different concentrations from each lectin to determine the maximum concentration without or with lowest cytotoxic effect. After, it was also measured the cytokine levels produced by these cells when stimulated by the selected concentrations of lectins. We found that ScLL showed high capacity to induce of pro-inflammatory cytokine production, while ArtinM was able to induce especially an anti-inflammatory cytokines production. Furthermore, both lectins were able to increase NO levels. Next, we evaluated the treatment effect of ScLL and ArtinM in C57BL/6 mice infected by ME49 strain from T. gondii. The animals were infected and treated with ScLL, ArtinM, ArtinM plus ScLL or sulfadiazine, and the following parameters analyzed: cytokines production, brain parasite burden and survival rates. Our results demonstrated that the ScLL or ScLL plus ArtinM treatment induced production of pro-inflammatory and anti-inflammatory cytokines, showing differential but complementary profiles. Moreover, when compared with non treated mice, the parasite burden was significantly lower and survival rates higher in mice treated with ScLL or ScLL plus ArtinM, similarly with sulfadiazine treatment. In conclusion, the results demonstrated the suitable potential immunotherapeutic effect of ScLL and ArtinM lectins to control acute toxoplasmosis in this experimental murine model

Retraction Note: New molecular tools in Neospora caninum for studying apicomplexan parasite proteins

This paper has been retracted at the request of the authors