Antibodies to the Plasmodium falciparum rhoptry protein RAP‐2/RSP‐2 in relation to anaemia in Cameroonian children

Abstract

Previous studies have implicated reactive antibodies to the low molecular weight rhoptry-associated proteins (RAP-1, RAP-2/RSP-2 and RAP-3) in erythroid cell destruction during Plasmodium falciparum infection. In this pilot study, the frequency, specificity and functional capacity of naturally acquired anti-RAP-2/RSP-2 antibodies were investigated in the sera of anaemic and nonanaemic malaria-infected Cameroonian children. All sera recognized RAP-2/RSP-2 by FACS, irrespective of the clinical status of the subjects. However, the anaemic children showed higher levels of IgG antibodies than the nonanaemic group, while both groups showed similar levels of IgM antibodies. Only few individuals had detectable levels of RAP-2/RSP-2-specific IgG1 and IgG3 subclass antibodies, while no IgG2 and IgG4 subclass antibodies were detected in these subjects. By ELISA, the anaemic group tended to show higher levels of antibodies to RAP-2/RSP-2 regarding all antibody classes tested, except for IgG4 and IgE. Unexpectedly, sera from the nonanaemic group activated complement to a greater extent than those from the anaemic group. These results need to be confirmed in extended studies but indicate that the effector functions of the RAP-2/RSP-2-reactive antibodies may be more important than their amounts. Such antibodies could play a role in both immunity and pathogenesis during P. falciparum infection.

Potential Immune Mechanisms Associated with Anemia in Plasmodium vivax Malaria: a Puzzling Question

“…On the other hand, experiments conducted with P. falciparum have shown that the tagging of the surface of noninfected RBCs by parasite proteins, as well as the tagging of the erythroid precursor cells in bone marrow, may elicit a specific antibody response, triggering phagocytosis and complement activation and inducing the clearance of these cells (128)(129)(130)(131). These data suggest that specific immune responses induced by some parasite antigens may contribute to malaria pathogenesis, playing a role in the development of malarial anemia.…”

Acquired antibody responses against merozoite surface protein-119 antigen during Plasmodium falciparum and P.vivax infections in South Indian city of Mangaluru

“…Studies in children with SA revealed that immune complex (IC) may contribute an important role in erythrocyte destruction leading to development of malarial anemia (Mibei et al 2005). Also, experiments with Pf showed that tagging the surface of uninfected RBCs and erythroid precursor cells in bone marrow by parasite proteins may elicit a specific antibody response, triggering phagocytosis and complement activation and inducing the clearance of these cells, eventually leading to anemia (Awah et al 2011(Awah et al , 2009Layez et al 2005;Sterkers et al 2007). It is clearly evident from the results of this study, that the circulatory levels of anti-MSP-1 19 antibodies were higher in patients with increased anemic severity during Pv and Pf infections.…”

The anaemia of Plasmodium vivax malaria

“…To compound the problem, reduced glutathione, which is necessary for protecting red cells against damaging oxygen species, is reported to be depleted in vivax malaria [93,122]. Infection with P. falciparum causes altered expression of complement components and deposition of parasite proteins on infected and uninfected red blood cells [88,92] (the latter sometimes associated with presence of specific immunoglobulins); facilitating opsonization and complement-mediated phagocytosis [89,91,123]. It is unknown whether these processes also occur in vivax anaemia.…”