Rhipicephalus microplus tick is the major ectoparasite in tropical and sub-tropical regions of the globe. Its hematophagous habit cause severe anemia, reduction in the production of meat and milk and can transmit pathogens such as Anaplasma and Babesia. The complex R. microplus-Babesia has a major impact in livestock production, although little is known about the mechanism of invasion and survival of Babesia genus.In the last few years several groups have been working in the characterization of key molecules to the protozoa life cycle, especially in Plasmodium falciparum, agent of malaria. Several merozoite surface molecules (MSA) were already described taking part in adhesion and invasion of erythrocytes. Protease also takes place in protozoan life cycle, both cysteine and serine proteases display key functions in invasion and degradation of erythrocytes. Similarly in Babesia sp several surface proteins were associated with adhesion of red blood cells (RBC) and as expected, the uses of antibodies against this class of molecules were able to diminish the infection in vitro. A few proteases have also been described in Babesia sp and their correlation to the infection and egress of RBC evaluated. Although the mechanism of action of proteases during infection is still unknown, one cannot deny its key importance to protozoan life cycle.For the last few years our group has been working in the study of proteases and their inhibitors in hematophagous arthropods and revealing its importance in the host-parasite interface. In order to contribute to the knowledge of apicomplexa proteases and its relevance to the parasite life cycle the goals of this projected are the functional characterization of two proteases, one cysteine peptidase and one subtilisin, found in the genome of B. bovis, also we intend to establish knock-out strains for both proteases and evaluate its role during infection of RBC and parasite survival.
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