Mosquito bites and stages specific antibody responses against Plasmodium falciparum in southern Ghana

Abstract

BackgroundThe human host elicits specific immune responses after exposure to various life stages of the malaria parasite as well as components of mosquito saliva injected into the host during a mosquito bite. This study describes differences in IgG responses against antigens derived from the sporozoite (PfCSP), asexual stage parasite (PfEBA175) and the gametocyte (Pfs230) in addition to an Anopheles gambiae salivary gland antigen (gSG6-P1) in two communities in Ghana with similar blood stage malaria parasite prevalence. MethodologyThis study used archived plasma samples collected from an earlier cross-sectional study that enrolled volunteers aged from 6 months to 70 years from Simiw, peri-urban community (N=347) and Obom, rural community (N=291). An archived thick and thin blood smear for microscopy was used for the estimation of Plasmodium parasite density and species and DNA extraction from blood spots and P. falciparum confirmation was performed using PCR. This study used the stored plasma samples to determine IgG antibody levels to Plasmodium falciparum and Anopheles salivary antigens using indirect ELISA. ResultsIndividuals from Simiw had significantly higher levels of IgG against mosquito gSG6-P1 (median (95%CI)) (2.590 (2.452-2.783) ng/mL) compared to those from Obom (2.119 (1.957-2.345) ng/mL), p<0.0001. Both IgG responses against Pfs230proC (p=0.0006), and PfCSP (p=0.002) were significantly lower in volunteers from Simiw compared to the participants from Obom. The seroprevalence of PfEBA-175.5R (p=0.8613), gSG6-P1 (p=0.0704), PfCSP (p=0.7798) IgG were all similar in Obom and Simiw. However, Pfs230 seroprevalence was significantly higher at Obom compared to Simiw (p=0.0006). Spearman correlation analysis showed no significant association between IgG responses against gSG6-P1, PfCSP, Pfs230proC and PfEBA-175.5R and parasite density at both Obom and Simiw (p>0.05). ConclusionIn conclusion, malaria transmission dynamics is highly complex. The similar malaria transmission intensity identified in the two communities resulted from a different combination of vector, environmental and host factors. With one community likely having a higher prevalence of uninfected mosquitoes and the other a larger reservoir of gametocyte carriers.