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The Plasmodium falciparum merozoite surface protein-1 19 KD antibody response in the Peruvian Amazon predominantly targets the non-allele specific, shared sites of this antigen.

Sutton PL, Clark EH, Silva C, Branch OH - Malar. J. (2010)

Bottom Line: The immuno-depletion ELISAs showed all samples responded to the antigenic sites shared amongst all allelic forms of PfMSP1-19KD.This has important implications for the use of PfMSP1-19KD as a vaccine candidate.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Medical Parasitology, New York University, New York, New York, USA.

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 PfMSP1-19KD and protection against febrile illness and parasitaemia. Therefore, some selection for PfMSP1-19KD allelic diversity would be expected if the protection is to allele-specific sites of PfMSP1-19KD. Here, the potential for allele-specific polymorphisms in this population is investigated, and the allele-specificity of antibody responses to PfMSP1-19KD are determined.

Methods: The 42KD region in PfMSP1 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 PfMSP1-19KD genetic diversity had any impact on antibody responses, ELISAs testing IgG antibody response were performed on individuals using all four allele-types of PfMSP1-19KD. 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 PfMSP1-19KD.

Conclusions: A non-allele specific antibody response in PfMSP1-19KD may explain why other allelic forms have not been maintained or evolved in this population. This has important implications for the use of PfMSP1-19KD as a vaccine candidate. It is possible that Peruvians have increased antibody responses to the shared sites of PfMSP1-19KD, 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.

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Experimental design for Antibody depletion ELISA. A representative sample is shown. Patients' sera were plated in duplicate and in 4 replicates in the first row on each type of "primary" plate (E-KNG, Q-KNG, E-TSR, and Q-TSR). The sera were then transferred down the plate seven times, incubating for half an hour before each transfer. After incubating the patient sera in the last row of the primary plate, it was transferred to a secondary plate of each allele.
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Figure 2: Experimental design for Antibody depletion ELISA. A representative sample is shown. Patients' sera were plated in duplicate and in 4 replicates in the first row on each type of "primary" plate (E-KNG, Q-KNG, E-TSR, and Q-TSR). The sera were then transferred down the plate seven times, incubating for half an hour before each transfer. After incubating the patient sera in the last row of the primary plate, it was transferred to a secondary plate of each allele.

Mentions: To evaluate the cross-reactivity of antibodies against each PfMSP1-19KD allele in sera samples from 18 different individuals, an ELISA was performed after antibody depletion with each of the allelic forms. This method was similar to the immunoassays used by Mamillapalli et al [14], where the assay was called "Antibody depletion ELISAs." After diluting the patient sera at 1:100 in AB Wash + 1.5% milk, the sera solution was placed in the first row of a 96-well primary plate (primary plates were coated with 50 ng of antigen per well in the first row of the plate and 100 ng of antigen per well in the seven consecutive rows). Patient sera were plated separately on E-KNG, Q-KNG, E-TSR, and Q-TSR primary plates. After incubating the sera for 30 min, it was then transferred to the next row of wells, where it was again incubated for 30 min. The wells of the primary plate were washed once with 50 μL of AB wash after each transfer, and the residual wash buffer was then placed with the sera to recover as much antibody as possible from the primary plates. Seven such transfers were performed. After the last transfer, the sera was transferred to secondary ELISA plates--one secondary plate for each of the four allele-types coated at 50 ng of antigen per well in all wells (Figure 2)--where it was incubated for one hour, and then the wells of both the primary and secondary plates were washed 4 times with AB wash and the ELISA was completed as described above in "Measurement of IgG."


The Plasmodium falciparum merozoite surface protein-1 19 KD antibody response in the Peruvian Amazon predominantly targets the non-allele specific, shared sites of this antigen.

Sutton PL, Clark EH, Silva C, Branch OH - Malar. J. (2010)

Experimental design for Antibody depletion ELISA. A representative sample is shown. Patients' sera were plated in duplicate and in 4 replicates in the first row on each type of "primary" plate (E-KNG, Q-KNG, E-TSR, and Q-TSR). The sera were then transferred down the plate seven times, incubating for half an hour before each transfer. After incubating the patient sera in the last row of the primary plate, it was transferred to a secondary plate of each allele.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2818648&req=5

Figure 2: Experimental design for Antibody depletion ELISA. A representative sample is shown. Patients' sera were plated in duplicate and in 4 replicates in the first row on each type of "primary" plate (E-KNG, Q-KNG, E-TSR, and Q-TSR). The sera were then transferred down the plate seven times, incubating for half an hour before each transfer. After incubating the patient sera in the last row of the primary plate, it was transferred to a secondary plate of each allele.
Mentions: To evaluate the cross-reactivity of antibodies against each PfMSP1-19KD allele in sera samples from 18 different individuals, an ELISA was performed after antibody depletion with each of the allelic forms. This method was similar to the immunoassays used by Mamillapalli et al [14], where the assay was called "Antibody depletion ELISAs." After diluting the patient sera at 1:100 in AB Wash + 1.5% milk, the sera solution was placed in the first row of a 96-well primary plate (primary plates were coated with 50 ng of antigen per well in the first row of the plate and 100 ng of antigen per well in the seven consecutive rows). Patient sera were plated separately on E-KNG, Q-KNG, E-TSR, and Q-TSR primary plates. After incubating the sera for 30 min, it was then transferred to the next row of wells, where it was again incubated for 30 min. The wells of the primary plate were washed once with 50 μL of AB wash after each transfer, and the residual wash buffer was then placed with the sera to recover as much antibody as possible from the primary plates. Seven such transfers were performed. After the last transfer, the sera was transferred to secondary ELISA plates--one secondary plate for each of the four allele-types coated at 50 ng of antigen per well in all wells (Figure 2)--where it was incubated for one hour, and then the wells of both the primary and secondary plates were washed 4 times with AB wash and the ELISA was completed as described above in "Measurement of IgG."

Bottom Line: The immuno-depletion ELISAs showed all samples responded to the antigenic sites shared amongst all allelic forms of PfMSP1-19KD.This has important implications for the use of PfMSP1-19KD as a vaccine candidate.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.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Medical Parasitology, New York University, New York, New York, USA.

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 PfMSP1-19KD and protection against febrile illness and parasitaemia. Therefore, some selection for PfMSP1-19KD allelic diversity would be expected if the protection is to allele-specific sites of PfMSP1-19KD. Here, the potential for allele-specific polymorphisms in this population is investigated, and the allele-specificity of antibody responses to PfMSP1-19KD are determined.

Methods: The 42KD region in PfMSP1 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 PfMSP1-19KD genetic diversity had any impact on antibody responses, ELISAs testing IgG antibody response were performed on individuals using all four allele-types of PfMSP1-19KD. 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 PfMSP1-19KD.

Conclusions: A non-allele specific antibody response in PfMSP1-19KD may explain why other allelic forms have not been maintained or evolved in this population. This has important implications for the use of PfMSP1-19KD as a vaccine candidate. It is possible that Peruvians have increased antibody responses to the shared sites of PfMSP1-19KD, 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.

Show MeSH
Related in: MedlinePlus