Plasmodium falciparum Specific IgE, IgG and Anti-GPI IgG Antibodies in Cameroonian Children with Severe and Uncomplicated Malaria

Abstract

Aims: We investigated the role of antibodies in the pathogenesis of severe malaria in children by measuring and comparing plasma levels of antibodies to glycosyl phosphatidy linositol (GPI) and crude Plasmodium falciparum extract.  Study Design: Cross-sectional case-control study. Place and Duration of Study: Five health institutions in two towns and seven primary schools in the South West region of Cameroon between April 2003 and December 2005. Methodology: A total of 649 children including 25, 156 and 233 cases of cerebral malaria (CM), severe malaria anaemia (SMA) and uncomplicated malaria (UM) respectively were recruited from health institutions and 233 apparently healthy controls (HC) from schools using predefined inclusion criteria. Malaria parasitaemia was determined by light microscopy using Giemsa-stained thick blood smears, haemoglobin level using a haemoglobinometer and blood cell count using a haemocytometer. The levels of total IgE, P. falciparum IgG, IgE and anti-GPI IgG antibodies were measured from plasma by the ELISA technique.  Results: The mean white blood cell count (WBC) was higher in the severe malaria group compared with the HC group. Geometric mean parasite densities were significantly different (P<0.001) amongst the study groups but similar in the two severe malaria groups (Severe Malaria Anaemia and Cerebral Malaria). Seropositivity for IgG antibodies to P. falciparum was different within the study groups (P<0.001) and higher in the clinical cases compared to the HC group. Mean levels of anti-GPI IgG and P. falciparum specific IgE and IgG antibodies were significantly different among the study participant categories. Mean plasma levels of these antibodies were higher in the UM and HC groups when compared with the severe malaria groups. There was a significant positive correlation between the age of the participant and levels of anti-GPI IgG (P<0.001), P. falciparum IgE (P = 0.027) and total IgE (P = 0.020) antibodies. Conclusion: Our observation of lower levels of anti-GPI and P. falciparum specific IgE antibodies in the severe group compared with the control group suggest a protective role of these antibodies in the pathogenesis of severe malaria. The correlation observed between P. falciparum IgE, IgG and GPI IgG antibody levels with age confirm previous reports that immunity to malaria develops with age and is partially dependent on antibody production.