Humoral immune IgG response to Plasmodium falciparum in adults: the role of subclass-IgG in clinical immunity to cerebral Malaria

ABSTRACT

Although antibodies are essential mediators of immunity, high levels of IgG antibodies against a wide range of blood-stage antigens of P. falciparum are poor predictors of clinical protection. It is the qualitative and the functional specificity of the antibodies to malaria antigens that predict the development of a clinically potent protective immunity. The objective of this work is to study the pattern of IgG sub-class in healthy and malaria-infected adults resident in a malaria-endemic area in Sudan. Total plasma IgG and IgG subclasses [IgG1, 2, 3 and 4] against the C-terminal region of the MSA-1[19] antigen of Plasmodium falciparum were measured by a quantitative enzyme-linked immunosorbent assay [ELISA] in 30 adult patients presenting to the emergency department with cerebral malaria [CM]. The levels of IgG antibody profile in CM patients were compared with those in patients with uncomplicated acute malaria [n=20] and in clinically healthy asymptomatic volunteers [n=20]. Total plasma IgG level was significantly higher in CM patients. The level of the sub-class IgG1 antibody against MSA-119 was significantly lower in patients infected with P. falciparum; the lowest values being observed in CM patients and the highest values in the clinically healthy volunteers. Our data suggest that acquisition of IgG1 antibody to MS A-1[19] is associated with a clinically protective immunity and that low production or defective IgG1 response may be associated with severe form of malaria in adults