Association of the IgG response to Plasmodium falciparum merozoite protein (C-terminal 19 kD) with clinical immunity to malaria in the Brazilian Amazon region.

Abstract

Abstract. The antibody response to the C-terminal 19-kD fragment of Plasmodium falciparum merozoite surface protein-1 (PfMSP1-19) was investigated in groups of subjects living in areas of Brazil with different levels of malaria transmission. The prevalence and the levels of IgG to PfMSP1-19 increased with the time of exposure and were positively correlated with the absence of clinical symptoms in parasitemic patients. The frequency of positive response and the mean level of IgG were higher in areas where malaria prevalence was more intense, especially among asymptomatic patients. The serum absorbance values of the IgG1 isotype were significantly higher among subjects with long-term exposure and in asymptomatic infections. These data suggest a protective role of IgG1 in naturally acquired immunity in spite of the unstable transmission levels in the Brazilian Amazon.

A Reduced Risk of Infection with Plasmodium vivax and Clinical Protection against Malaria Are Associated with Antibodies against the N Terminus but Not the C Terminus of Merozoite Surface Protein 1

“…The existence of asymptomatic plasmodial infections in Brazil allowed the initiation of studies to look for associations of antibodies against parasite antigens with clinical protection (5,23). Interestingly, these two reports used the same human populations to look for associations of acquired immunity with IgG subclasses against the C terminus of the MSP1 proteins from P. falciparum (5) and P. vivax (23).…”

“…Interestingly, these two reports used the same human populations to look for associations of acquired immunity with IgG subclasses against the C terminus of the MSP1 proteins from P. falciparum (5) and P. vivax (23). The criteria used to define asymptomatic individuals in these studies (Giemsa-positive or PCR-positive patients that did not develop symptoms after 72 h of this detection), however, is not stringent enough to discount the possibility that these could later turn into symptomatic patients.…”

Naturally acquired antibodies to merozoite surface protein (MSP)-1(19) and cumulative exposure to Plasmodium falciparum and Plasmodium vivax in remote populations of the Amazon Basin of Brazil

“…Elisa for IgG antibodies -Assays with PfMSP-1 were performed as described (Braga et al 2002). Highbinding 96-well microplates (Nunc Maxisorp, Denmark) were coated with 50 ng of PfMSP-1 per well, dissolved in 50 µl of 0.1 M carbonate-bicarbonate buffer (pH 9.6) and incubated overnight at 4 o C. Serum samples (50 µl/ well) were tested at 1:50 dilution (PfMSP-1 19 ); these working dilutions were determined by checkerboard titration of positive and negative control sera.…”

“…In addition, levels of naturally acquired anti-P. falciparum (PfMSP1 19 ) antibodies measured with conventional enzyme-liked immunosolvent assay (ELISA) have been positively associated with protection from P. falciparum infections in some (Egan et al 1996, Branch et al 2000, although not all (Dodoo et al 1999, Riley et al 2000 African cohorts. In Brazil, there is evidence from cross-sectional studies of an association between levels of antibodies to MSP-1 19 and reduced risk of clinical malaria (Braga et al 2002). However, it remains unknown whether all antibodies to PfMSP-1 19 detected by ELISA are functionally relevant.…”

Cross-reactive anti-PfCLAG9 antibodies in the sera of asymptomatic parasite carriers of Plasmodium vivax

“…Antibody reactivity to synthetic peptides in sera of malaria patients -All serum samples from malaria patients as well as negative controls were tested in duplicate by the enzyme-linked-immunosorbent-assay (ELI-SA) as described by Braga et al (2002). This test was performed thrice.…”