Author:
Sutton Patrick L,Clark Eva H,Silva Claudia,Branch OraLee H
Abstract
Abstract
Background
Plasmodium falciparum re-emerged in Iquitos, Peru in 1994 and is now hypoendemic (< 0.5 infections/person/year). Purportedly non-immune individuals with discrete (non-overlapping) P. falciparum infections can be followed using this population dynamic. Previous work demonstrated a strong association between this population's antibody response to Pf MSP1-19KD and protection against febrile illness and parasitaemia. Therefore, some selection for Pf MSP1-19KD allelic diversity would be expected if the protection is to allele-specific sites of Pf MSP1-19KD. Here, the potential for allele-specific polymorphisms in this population is investigated, and the allele-specificity of antibody responses to Pf MSP1-19KD are determined.
Methods
The 42KD region in Pf MSP1 was genotyped from 160 individual infections collected between 2003 and 2007. Additionally, the polymorphic block 2 region of Pfmsp1 (Pfmsp1-B2) was genotyped in 781 infection-months to provide a baseline for population-level diversity. To test whether Pf MSP1-19KD genetic diversity had any impact on antibody responses, ELISAs testing IgG antibody response were performed on individuals using all four allele-types of Pf MSP1-19KD. An antibody depletion ELISA was used to test the ability of antibodies to cross-react between allele-types.
Results
Despite increased diversity in Pfmsp1-B2, limited diversity within Pfmsp1-42KD was observed. All 160 infections genotyped were Mad20-like at the Pfmsp1-33KD locus. In the Pfmsp1-19KD locus, 159 (99.4%) were the Q-KSNG-F haplotype and 1 (0.6%) was the E-KSNG-L haplotype. Antibody responses in 105 individuals showed that Q-KNG and Q-TSR alleles generated the strongest immune responses, while Q-KNG and E-KNG responses were more concordant with each other than with those from Q-TSR and E-TSR, and vice versa. The immuno-depletion ELISAs showed all samples responded to the antigenic sites shared amongst all allelic forms of Pf MSP1-19KD.
Conclusions
A non-allele specific antibody response in Pf MSP1-19KD may explain why other allelic forms have not been maintained or evolved in this population. This has important implications for the use of Pf MSP1-19KD as a vaccine candidate. It is possible that Peruvians have increased antibody responses to the shared sites of Pf MSP1-19KD, either due to exposure/parasite characteristics or due to a human-genetic predisposition. Alternatively, these allelic polymorphisms are not immune-specific even in other geographic regions, implying these polymorphisms may be less important in immune evasion that previous studies suggest.
Publisher
Springer Science and Business Media LLC
Subject
Infectious Diseases,Parasitology
Cited by
18 articles.
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