Leishmania virulence factors and host peptidases associated with visceral leishmaniasis

Leishmaniasis is a severe disease of humans and one of the world's most neglected diseases, primarily affecting the poor in developing countries. 350 million people are at risk of contracting the disease and it has severe costs in both health and economic terms and drains resources that could be used to promote growth of developing nations. There is no effective vaccine against the disease and chemotherapy is the prime means for reducing the leishmaniasis burden. Visceral Leishmaniasis (VL) is the most severe form of leishmaniasis with 6,000 cases recorded in Brazil each year. Unfortunately the drugs available to treat VL have many limitations and new drugs are desperately needed. Our aim in this collaborative project is to characterise key biological processes of Leishmania chagasi, the parasite that causes VL in Brazil, and so identify factors that influence the outcome of disease. We have shown that peptidases, enzymes that digest proteins, and natural inhibitors that block peptidase function, are important in the infectivity and pathogenicity of the parasite. Our work will concentrate on 3 key areas of the biology of the parasite and its interaction with the host. Firstly, we will test if peptidases in the mammalian host are important for the pathogenesis of the disease. To do this we will use an animal model of infection using the L. chagasi parasite and mice. A key approach will be to genetically manipulate important Leishmania genes to find out what role the encoded proteins play in the parasite's infectivity and virulence and to determine whether they might be exploited as novel therapeutics. Secondly, we shall investigate the genome variation that occurs in different strains of Leishmania. We will sequence the genomes of L. chagasi parasites isolated from patients in the State of Piaui in Brazil with different clinical VL outcome and identify parasite genes that might influence the presentation of disease. We will integrate parasitological and immunological studies in animal models and humans and overall, we expect the outcome from this study to be a greatly improved understanding on the roles of these biological processes in Leishmania, and the molecular mechanisms of the processes themselves - which will be relevant to many areas of biology.

In Brazil, visceral leishmaniasis (VL) is caused by Leishmania chagasi. In this proposal we aim to investigate virulence factors and
pathways contributing to pathology in visceral leishmaniasis by comparing organ specific responses to infection using animal models
(UFRJ and UK) with natural infection in a clinical setting (UFPI). It is well established that neutrophils are important in establishment of
infection with Leishmania and we have preliminary data indicating that the parasite virulence factor inhibitor of serine peptidase (ISP2) and
the host serine peptidase neutrophil elastase (NE) influence infection of macrophages with L. donovani and that NE might link to bone marrow
failure. We hypothesize that serine peptidases of the host are important for disease outcome in experimental VL. We aim to: (1)
identify the underlying molecular mechanisms using L. chagasi and L. donovani mutants lacking ISP2 and gene deficient mice lacking NE and
cathepsin G. (2) test if clinical L. chagasi isolates modulate host serine peptidases to influence infection in a similar way to L.
donovani; (3) investigate the possible association between parasite genotype and disease presentation in Brazilian patients with VL, with
a view to understanding whether the interaction between serine peptidases and parasite ISP2 plays a role in pathogenesis.

The work we propose to undertake will contribute to delivery of Strategic Aim 3 of the MRC Strategic Plan 2014-2019 by forming international partnerships and accelerating progress in international health research that addresses inequalities in health. The research falls within the remit of the MRC's research priority theme one: Natural Protection.

Academic impact
1. The attainment of new knowledge, innovation and scientific advancement on the genetics and cell biology of parasitic protozoa that cause the neglected infectious disease Visceral Leishmaniasis (VL) in Brazil.
2. A deeper understanding of the immunological interaction of Leishmania with its host, which will help to provide solutions to the control of VL endemic in Brazil and other developing countries.
3. The provision of new tools, innovative methods for genetic manipulation of Leishmania and reagents to academic partners for the study of the molecular genetics, biochemistry and cell biology of Leishmania.
4. Delivery and training of highly skilled researchers in parasitology, molecular genetics and genomics.

Economic and societal impact
1. The work aims to investigate fundamental aspects of the biology of Leishmania chagasi, which causes important and widespread disease in humans and companion animals (dogs) in Brazil. The work is unlikely to lead to any immediate commercial exploitation, although understanding the mechanisms by which Leishmania interacts with its host may ultimately lead to the development of new diagnostics, drugs or vaccines.
2. Enhancing the quality of life in countries endemic for VL, in particular Brazil
3. Potential to change the effectiveness of clinical practice in Brazil and other endemic areas (through a detailed understanding of the pathogenesis of VL)
4. To enhance the capacity of the UFRJ and UFPI to carry out basic and applied research into visceral leishmaniasis.
5. To ensure our work is ODA compliant.