Community Research and Development Information Service - CORDIS

Periodic Report Summary 1 - GUTTRYP (The role of the gut in experimental visceral leishmaniasis and Chagas disease)

• Summary description of the project objectives

Leishmania donovani and Trypanosoma cruzi cause the neglected infectious diseases visceral leishmaniasis (VL) and Chagas disease (CD) respectively. The host normally controls the initial wave of infection but rarely, if ever, fully clears the infection. Chronic, low-level infection then often progresses to serious clinical syndromes. Infection of a limited set of favoured tissues is a parasite strategy to evade host immunity and maintain chronicity. Previous work had shown that the gut is a site of chronic T. cruzi infection in CD mouse models. L. donovani persists in liver and spleen, but the gut may also be a target. In cutaneous leishmaniasis, chronic persistence occurs in the skin due to unique immune responses that evolved to tolerate constant exposure to the outside environment. A similar situation exists in the gut, where inflammatory responses against commensal microbe and food antigens are usually unwarranted and potentially dangerous. As in the skin, the hyporesponsive environment of the gut may underpin host failure to clear T. cruzi and L. donovani. Persistence in the gut may compromise microbiota containment leading to secondary syndromes, a situation seen in other chronic infections such as HIV and Toxoplasmosis, or exacerbate VL/CD pathology.

The first phase of this project aimed to test the hypothesis that the gut and its microbiota are important factors in visceral leishmaniasis. To do this several objectives were developed to study L. donovani infections using animal models. These objectives included a) an assessment of the relevance of the gut as a site of L. donovani persistence; b) analyses of gut-specific responses to L. donovani in comparison to other known sites of persistence; and c) investigation of interactions between the animal host, the parasite and host gut’s commensal microbiota

The training programme associated with the work towards these research objectives was designed to enable the fellow to develop a broad range of new skills, particularly in immunology. Newly acquired technical and conceptual competencies would then allow the fellow to conduct further research into T. cruzi persistence during the second phase of the project.

• Description of the work performed since the beginning of the project

In the early stages of the project I focussed on developing experimental tools to enable the planned research objectives to be met. This included genetically engineering Leishmania parasites to express and secrete a defined model antigen termed 2W1S. I then conducted a series of experiments to optimise protocols that would enable a mouse’s immune response to those parasites to be analysed using flow cytometry. I also used two different approaches to look for infection in the tissues of the GI tract in both the mouse and hamster models of visceral leishmaniasis. Firstly, I used quantitative PCR to detect parasite DNA and secondly flow cytometry to screen single cells derived from GI tract tissue for the presence of parasites tagged with a red fluorescent protein.

In order to investigate a potential role for the host gut microbiota in visceral leishmaniasis we performed experiments to compare the outcome of L. donovani infection in both mice and hamsters that were continuously treated with multiple antibiotics with untreated control animals. The antibiotic treatment was designed to remove the majority of the bacterial species normally present in the rodent’s GI tracts. Promising results led us to investigate many aspects of leishmaniasis in these “dysbiotic” animals, including the intensity of the infection, the pathology caused by it in different organs and the associated immune responses.

• Description of the main results achieved so far

The data indicated that transgenic parasites engineered to express the 2W1S antigen could be a useful experimental tool to study immune responses in mice. The technology is not transferable to the hamster model due to genetic differences compared with mice and a lack of suitable reagents. The data showed that L. donovani parasitized the tissues of the GI tract in symptomatic hamsters but not in asymptomatic mice. Hamsters in the antibiotic treatment groups had delayed onset and progression symptoms. Hamsters that were infected with L. donovani and also treated with antibiotics survived for significantly longer than hamsters that did not receive antibiotics. Antibiotic-treated hamsters also had significantly less tissue pathology than untreated controls even though infection intensities were not significantly different. There were no significant differences in disease presentation in mice with antibiotic-induced dysbiosis.

• Expected final results and their potential impact and use

Beyond the main results already obtained, which are outlined in the previous section, it is not possible to predict the final results of ongoing or future experiments. Nevertheless, by the end of the project, the research will provide a clearer idea of when, how and why parasitic protozoa can persistently infect the gastrointestinal tract. In addition, they will provide a better understanding of the impact of the host’s microbiota on the outcome of infection with both L. donovani and T. cruzi. I expect to publish the results of the work in at least two peer-reviewed publications that will be made open-access. I have gained considerable experience in terms of both scientific and complementary skills that will help me to make a fuller contribution to research and education.

So far the project has not had a noticeable socio-economic impact nor obvious societal implications. The data obtained indicate that the utility of antibiotic prophylaxis as an adjunct therapy for humans suffering from visceral leishmaniasis is worthy of further investigation. All of the insights gained into the biology of visceral leishmaniasis and Chagas disease will add to the overall understanding of these neglected infections and inform efforts to develop better ways to control and treat them.

Contact

Andrews Chris, (Research Operations Manager)
Tel.: +44 2079272486
E-mail

Subjects

Life Sciences
Record Number: 195336 / Last updated on: 2017-03-13
Follow us on: RSS Facebook Twitter YouTube Managed by the EU Publications Office Top