Natural antibody responses to Plasmodium falciparum MSP3 and GLURP(R0) antigens are associated with low parasite densities in malaria patients living in the Central Region of Ghana

Abstract

Background Plasmodium falciparum genetic diversity and multiplicity of infection (MOI) are parasite features that have been suggested to influence the acquisition of protective immunity against malaria. This study sought to assess the relationship between MOI and parasite density (PD) in malaria patients living in the Central Region of Ghana and to determine whether naturally occurring antibody levels against P. falciparum GLURP (PF3D7_1035300) and MSP3 (PF3D7_1035400) antigens are associated with decreased parasite load.MethodsDried filter paper blood blots were obtained from children and adults diagnosed with uncomplicated P. falciparum malaria. Microscopy was used to estimate P. falciparum parasite density and polymerase chain reaction (PCR) amplification of the polymorphic regions of msp1 (PF3D7_0930300) and msp2 (PF3D7_0206800) was used for parasite genotyping and MOI determination. ELISA was used to measure the serum IgG concentration of R0 fragment of GLURP (GLURP(R0)) and MSP3 antibodies.ResultsAll 115 samples were positive for P. falciparum by PCR using either the msp1 or msp2 genotyping primer sets. The most prevalent msp1 and msp2 alleles were KI and 3D7, respectively. The geometric mean (GM) for MOI determined by both msp1 and msp2 genotyping was 1.3 for the entire population and was generally higher in children than in adults. Seropositivity was estimated at 67 and 63% for GLURP(R0) and MSP3 antibodies, respectively, and antibody titers were negatively correlated with parasite density.ConclusionsThe negative correlation between naturally occurring GLURP(R0) and MSP3 antibody levels and parasite density observed in this study suggest that augmenting the antibody response with the GMZ2 vaccine could enhance protection in the Central Region of Ghana.Electronic supplementary materialThe online version of this article (doi:10.1186/s13071-017-2338-7) contains supplementary material, which is available to authorized users.

Plasmodium falciparum strains spontaneously switch invasion phenotype in suspension culture

“…To determine if the Dd2 and W2mef cultures were contaminated with 3D7 or another SA-independent parasite strain, we sought to confirm the genetic identities of both Static and Suspended cultures of all three strains. Using the highly polymorphic merozoites surface protein 2 (MSP2) and previously described procedures 33 – 35 we confirmed that Suspended cultures of Dd2, W2mef and 3D7, were genetically identical to their respective Static cultures (Supplementary Figure S1 ). Furthermore, we found that erythrocyte surface expression levels of SA and CR1 were not significantly altered due to shaking (Supplementary Figure S2a and b ).…”

Seasonal variations in Plasmodium falciparum genetic diversity and multiplicity of infection in asymptomatic children living in southern Ghana

“…Total genomic DNA (gDNA) was extracted from the dried blood spot (DBS) using the Chelex extraction procedure [ 40 , 41 ]. Briefly, two 3 mm discs were punched out from the dried blood spots into 1.5 mL microcentrifuge tubes containing 1 mL of 1X phosphate buffered saline (PBS).…”

Stage-specific Plasmodium falciparum immune responses in afebrile adults and children living in the Greater Accra Region of Ghana

“…Antibody responses including IgG, IgM, IgG1, and IgG3 against recombinant P. falciparum sexual stage and asexual stage antigens were quantified using an indirect ELISA protocol [41]. The antigens used in this study include Pfs230 [14] and MSP3 [30] produced in Lactococcus lactis. Briefly Pfs230 antigen was diluted to 1 µg/ ml in carbonate buffer [14,15] and MSP3 diluted to 1 µg/ ml in phosphate-buffered saline (1X PBS, pH7.2) [15,30] and 100 µl/well of the diluted antigen was used to coat the wells of Maxisorp NUNC plates (Nunc Maxisorp, UK) overnight at 4 °C.…”

“…The antigens used in this study include Pfs230 [14] and MSP3 [30] produced in Lactococcus lactis. Briefly Pfs230 antigen was diluted to 1 µg/ ml in carbonate buffer [14,15] and MSP3 diluted to 1 µg/ ml in phosphate-buffered saline (1X PBS, pH7.2) [15,30] and 100 µl/well of the diluted antigen was used to coat the wells of Maxisorp NUNC plates (Nunc Maxisorp, UK) overnight at 4 °C. The plates were subsequently washed with wash buffer (PBST; 1X PBS supplemented with 0.05% Tween 20 at pH7.2), blocked with 3% nonfat skimmed milk (Marvel, UK) in1X PBS and incubated at room temperature (RT) for 1 h. The plates were then incubated with 100 µl/well of plasma diluted to 1:200 for IgG and IgM and 1:100 for IgG1 and IgG3 in 1% of non-fat skimmed milk in 1X PBS.…”

“…Monitoring antibody responses in asymptomatic individuals is thus a valuable tool for monitoring the acquisition of anti-disease immunity as well as the frequency and magnitude of parasite infection [1]. A few earlier studies have characterized natural antibody responses to both asexual and sexual stage antigens, however these studies have only looked into immune responses in asymptomatic children below the age of 12 years [15] or in a symptomatic population [30]. Other studies on afebrile individuals have characterized antibody responses against sporozoite [31], asexual [32,33] or only sexual stage [34] antibody responses amongst a cohort of Ghanaians.…”