Evaluation of the genetic polymorphism of Plasmodium falciparum P126 protein (SERA or SERP) and its influence on naturally acquired specific antibody responses in malaria-infected individuals living in the Brazilian Amazon.

Background: The Plasmodium falciparum P126 protein is an asexual blood-stage malaria vaccine candidate antigen. Antibodies against P126 are able to inhibit parasite growth in vitro, and a major parasite-inhibitory epitope has been recently mapped to its 47 kDa N-terminal extremity (octamer repeat domain--OR domain). The OR domain basically consists of six octamer units, but variation in the sequence and number of repeat units may appear in different alleles.

Merozoite surface protein 2 allelic variation influences the specific antibody response during acute malaria in individuals from a Brazilian endemic area.

The antibody response to Plasmodium falciparum parasites of naturally infected population is critical to elucidate the role of polymorphic alleles in malaria. Thus, we evaluated the impact of antigenic diversity of repetitive and family dimorphic domains of the merozoite surface protein 2 (MSP-2) on immune response of 96 individuals living in Peixoto de Azevedo (MT-Brazil), by ELISA using recombinant MSP-2 proteins. The majority of these individuals were carrying FC27-type infections.

Plasmodium falciparum: limited genetic diversity of MSP-2 in isolates circulating in Brazilian endemic areas.

The genetic polymorphism of the surface merozoite protein 2 (MSP-2) was evaluated in Plasmodium falciparum isolates from individuals with uncomplicated malaria living in a Brazilian endemic area of Peixoto de Azevedo. The frequency of MSP-2 alleles and the survival of genetically different populations clones in 104 isolates were verified by Southern blot and SSCP-PCR. Single and mixed infections were observed in similar frequencies and the rate of detection of FC27 and 3D7 allelic families was equivalent.

Plasmodium falciparum: a comparative analysis of the genetic diversity in malaria-mesoendemic areas of Brazil and Madagascar.

For a better definition of the polymorphic features of Plasmodium falciparum parasite populations, the polymerase chain reaction (PCR) typing technique was used to investigate the genetic diversity and complexity of parasites harbored by acute P. falciparum carriers from three yet unexplored malaria-mesoendemic areas with different transmission levels: two localities in northwestern Brazil (Ariquemes and Porto Velho) and a village in Madagascar (Ankazobe). A total of 89 DNA samples were analyzed by amplification of polymorphic domains from genes encoding merozoite surface antigens 1 and 2 (MSP-1, MSP-2) and thrombospondin-related anonymous protein (TRAP) and by hybridization with allelic-family-specific probes or random-fragment-length polymorphism (RFLP).

Rapid turnover of Plasmodium falciparum populations in asymptomatic individuals living in a high transmission area.

A polymerase chain reaction (PCR) typing technique, based on the amplification of polymorphic regions from the merozoite surface protein 1 (MSP-1) and MSP-2 Plasmodium falciparum genes, was used to characterize parasites collected in a longitudinal study of asymptomatic carriers of malaria parasites living in two distinct epidemiologic situations. Blood samples were collected from children and adults living in the village of Dielmo, Senegal, when malaria transmission was 3-6 infective bites/week/individual. For each individual, every sample collected at two-week intervals over a period of three months showed a specific PCR pattern.

Conservation of the Plasmodium falciparum sporozoite surface protein gene, STARP, in field isolates and distinct species of Plasmodium.

The extent of structural conservation of the Plasmodium falciparum sporozoite surface protein gene, STARP, recently characterized in the T9/96 clone, has been analyzed using the polymerase chain reaction. Results from Ivory Coast and Thai clones, field isolates originating from Brazil and Kenya and laboratory-maintained strains strongly suggest that this gene has a highly conserved structure throughout this species. This structure includes a complex repetitive central domain consisting of a mosaic region followed by tandem 45-amino acid-encoding (Rp45) and 10-amino acid-encoding (Rp10) repeat regions.