IgG isotype to C-terminal 19�kDa of Plasmodium vivax merozoite surface protein 1 among subjects with different levels of exposure to malaria in Brazil

Abstract

Subclasses of antibodies to the C-terminal 19 kDa fragment of the Plasmodium vivax merozoite surface protein 1 (PvMSP-1(19)) were assessed among subjects with distinct degrees of malaria exposure in the Brazilian endemic area. The PvMSP-1(19) specific IgG1and IgG3 levels were low among subjects with long-term exposure (approximately 19 years) when compared to subjects less and sporadically exposed (<1 year). No statistically difference was observed in IgG subclass distribution of antibodies from symptomatic Plasmodium-infected patients, asymptomatic parasite carriers and non-infected subjects living in a same mesoendemic area. Subjects briefly exposed to a P. vivax outbreak living in a rural community outside the endemic area were also evaluated to measure the persistence of specific antibodies. IgG anti-PvMSP-1(19) antibodies persisted in 40% of the subjects who had had malarial symptoms 8 months before and decreased after 7 years (28%). Specific IgG1 were the predominant isotype. Our study emphasizes the highly immunogenicity of the PvMSP-1(19) and points toward its possible use as a potential malaria vaccine.

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

“…2 and Table 3). This result is thus in agreement with the one reported previously for this portion of PvMSP1 (23). In contrast, immune sera from these same patients revealed a highly statistically significant association of antibodies against the N terminus of PvMSP1 with clinical protection and reduced risk of P. vivax infection over the 1-year follow-up period.…”

“…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. Regardless, the results suggested that there is an association of clinical protection with IgG1 subclass antibodies against the C terminus of P. falciparum (5), whereas no association with regard to antibodies or subclasses could be supported against the C terminus of P. vivax (23). In contrast to the above studies, we looked for associations of clinical protection and reduced risk of infection with serology against PvMSP1 in a human population in which symptomless P. vivax-infected individuals have been unarguably found.…”

“…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

“…Contrasting with the extensive investigation of the role of Pf MSP-1 19 in naturally acquired immunity, little is known about the immune recognition of the ortholog protein of P. vivax (Pv). In Brazil, high proportions of subjects with detectable antibodies and T-cell responses to PvMSP-1 19 were found in areas of focal transmission (Soares et al 1997(Soares et al , 1999b and high proportions of seropositive subjects were uniformly observed in areas with more stable transmission (Morais et al 2005).…”