Genomics and post-genomics approaches to study the human malarial parasites Plasmodium vivax and Plasmodium falciparum in the Brazilian Amazon

Abstract

In the area of molecular biology, we have constructed a genomic DNA library of P. vivax (the most prevalent malarial parasite in Latin America and responsible for 80 million annual cases worldwide), in yeast artificial chromosomes (YACs) with parasite material obtained from a single infected patient in the Brazilian Amazon. Generating an unlimited source of parasite material was of particular relevance since P. vivax cannot be maintained continuously in in vitro culture. Significantly, the availability of this reference library enabled us to apply comparative genomics to address different aspects of the pathology associated with P. vivax infections such as antigenic variation, chloroquine resistance and identification of mapped microsatellite markers for populational studies (unpublished). We are now following up these studies given particular emphasis to the vir genes of P. vivax to study their role in natural and experimental infections. Thus, we are analyzing the expression of vir genes in parasites obtained directly from human patients as well as trying to determine their expression in single-infected cells. Moreover, using transfection technologies we are trying to express these genes in P. falciparum to determine their role in virulence. Other molecular biology studies in Plasmodium have been or are presently being pursued in the laboratory, including one on the var multigene family of P. falciparum in the Brazilian Amazon (see publications), and attempts to establish an inducible system based on a transcriptional transactivator in Plasmodium (unpublished) In the area of vaccine development, we have concentrated our efforts on the merozoite surface protein 1 of P. vivax (PvMSP1), and in particular on the C-terminal region of the molecule, PvMSP119. We have chosen PvMSP119 since studies on naturally acquired immunity of vivax patients from the Brazilian Amazon have revealed that this is the most immunogenic portion of PvMSP1 and the only portion capable of eliciting a boost effect upon new infections. Thus far, we have generated an inmunogenic DNA recombinant plasmid of PvMSP119, and an inmunogenic transgenic Toxoplasma gondii expressing PvMSP119 (unpublished). Both constructs are now being tested in preclinical trials and a transgenic P. falciparum expressing PvMSP119 to address the importance of antibodies in the elicited responses from monkeys, is being generated.