Studies on Stage Regulated Gene Expression in Leishmania donovani Isolated from Indian Kala Azar Patients using Genomic Microarrays

Abstract

Leishmaniasis, a vector-borne disease that is caused by obligate intra-macrophage protozoa, is endemic in large areas of the tropics, subtropics and the Mediterranean basin. This disease is characterized by both diversity and complexity (Herwaldt, 1999): it is caused by more than 20 leishmanial species and is transmitted to humans by ~30 different species of phlebotomine sandflies (Pearson and Sousa, 1996). newlineThe two major clinical forms of ieishmaniasis, cutaneous and visceral, are the result of infection by different species of the parasite. However, in addition to the infecting species, the clinical outcome of leishmaniasis also depends on the immune response of the host (Rivas et al., 2004). Epidemiology, immunopathology and outcome are similarly diverse, since infection occurs in multiple endemic regions, in both children and adults (Herwaldt, 1999; Desjeux, 1999). Environmental risk factors such as massive displacement of populations, urbanization, deforestation, new irrigation plans and individual risk factors such as HIV, malnutrition and genetic susceptibility make leishmaniasis an important public health problem (Desjeux, 2004). Though the most significant public health effects of leishmaniasis are concentrated in developing countries, occasional cases occur in developed countries as well. Visceral leishmaniasis, fatal if not treated, is caused by parasites of L.donovani complex comprising of L.donovani, L.infantum, and L.chagasi. More than 90% of the visceral cases in the world are reported from Bangladesh, Brazil, India and Sudan (Desjeux, 1992). In India, the official estimate of 430,000 VL cases in Bihar state over the past 11 years may represent only a fraction of the real numbers. The actual number is believed to be at least 5 times as great (Monograph, 1991-1996). newlineCurrent treatment of leishmaniasis is based on chemotherapy, which is difficult to administer, expensive and becoming ineffective due to the emergence of drug resistance.