Malaria can present itself as an uncomplicated or severe disease. We have here studied the quantity and quality of antibody responses against merozoite antigens, as well as the multiplicity of infection (MOI) in children from Uganda. We found higher levels of IgG antibodies towards EBA181, MSP2-3D7/FC27 and AMA1 in patients with uncomplicated malaria by ELISA, but no differences against EBA140, EBA175, MSP1, Rh2 and Rh4 or for IgM against MSP2-3D7/FC27. Patients with uncomplicated malaria were also shown to have higher antibody affinities for AMA1 by surface plasmon resonance (SPR). Decreased invasion of two clinical P. falciparum isolates in presence of patient plasma correlated with lower initial parasitemia in the patients, in contrast to comparisons of parasitemia to ELISA or affinity that did not show any correlations.Analysis of the heterogeneity of the infections revealed a higher MOI in patients with uncomplicated disease, with MSP1-K1 and MSP2-3D7 being the most discriminative allelic markers. Higher MOI also correlated positively with higher antibody levels in several of the ELISAs.In conclusion, certain antibody responses and MOI were associated with differences between uncomplicated and severe malaria. When combining different assays, some antibodies like those against AMA1 seemed particularly discriminative. However, only decreased invasion correlated with initial parasitemia in the patient, signaling the importance of functional assays in understanding development of immunity against malaria and for evaluation of vaccine candidates.
Author’s full text available at link on right hand side of this page. Final publisher’s version of this article is available at http://cvi.asm.org/content/20/8/1170.long