Centers for Disease Control, Public
Health Services. U.S. Department of Health and Human Services. Division of Parasitic Diseases, National Center for Infectious Diseases. Malaria Branch. Atlanta GA, USA.Centers for Disease Control, Public
Health Services. U.S. Department of Health and Human Services. Division of Parasitic Diseases, National Center for Infectious Diseases. Malaria Branch. Atlanta GA, USA.Ministério da Saúde. Fundação Nacional de Saúde. Instituto Evandro Chagas. Belém, PA, Brasil.Governo do Estado de São Paulo. Superintendência de Controle de Endemias. Malaria Department. São Paulo, SP, Brazil.Papua New Guinea Institute of Medical Research.
Goroka, PNG.The circumsporozoite (CS) protein that covers the surface of infectious sporozoites is a candidate antigen in malaria
vaccine development. To determine the extent of B- and T-epitope polymorphism and to understand the mechanisms of
antigenic variability, we have characterized the CS protein gene of Plasmodium vivax from field isolates representing
geographically distant regions of Papua New Guinea (PNG) and Brazil. In the central repeat region of the CS protein, in
addition to variation in the number of repeats, an array of mutations was observed which suggests that point mutations have
led to the emergence of the variant CS repeat sequence ANGA(G/D)(N/D)QPG from GDRA(D/A)GQPA. Outside the
repeat region of the protein, the nonsilent nucleotide substitutions of independent origin are localized in three domains of the
protein that either harbor known T-cell determinants or are analogous to the Plasmodium falciparum immunodominant
determinants, Th2R and Th3R. We have found that, with the exception of one CS clone sequence that was shared by one P.
vivax isolate each from PNG and Brazil, the P. vivax CS protein types can be grouped into Papuan and Brazilian types. These
results suggest that an in-depth study of parasite population dynamics is required before field trials for vaccine formulations
based on polymorphic immunodominant determinants are conducted
