Toll-Like Receptors and Leishmaniasis

Abstract

More than 10 million people around the world are currently affected by Leishmania sp. (33). Infection with this protozoan parasite continues to be a problem in underdeveloped countries and is a continuous worry in developed countries due to the possibility of the disease afflicting tourists returning from countries where the organism is endemic (82). Leishmaniasis is a neglected infectious disease, and it affects poor and marginalized populations. It is distributed, in its visceral, mucosal, and cutaneous forms, throughout more than 90 countries in Africa, the Americas, Asia, and Europe (5). It constitutes a serious public health problem and causes significant morbidity and mortality. In recent years, economic globalization and the increase in travel have extended the distribution of the disease to developed countries. Approximately 350 million people live in areas where there is active parasite transmission of zoonotic and anthroponotic leishmaniasis. Zoonotic transmission occurs in rural and periurban environments, whereas anthroponotic transmission occurs in urban environments (7). From a strictly biological point of view, de Almeida et al. described humans as just one of the actors in the leishmaniasis drama (23). Also involved are the parasite, the insect, and other hosts. Several immunological studies have increased our understanding of the adaptive response in leishmaniasis. Thus, this disease has been used as a model of Th1 and Th2 responses. Unfortunately, there are still several aspects of the initial steps of Leishmania infection in humans that are largely unknown.