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

Mazin M T Shigidi, MBBS*, MD, Rihab A Hashim, BSc, MSc*,
Maowia M Mukhtar, B VSc, MSc, PhD**, Mohamed NA Idris, MD, DCN*,
Tag-Eldin O Sokrab,MD, PhD.***
Department of Medicine, Faculty of Medicine, University of Khartoum, Sudan*
Institute of Endemic Diseases, University of Khartoum, Sudan**
Department of Medicine, Hamad General Hospital, Doha, Qatar***

Background
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
 

Methods
Total plasma IgG and IgG subclasses (IgG1, 2, 3 and 4) against the C-terminal region of the MSA-119 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).

Results

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.
 

Conclusion

Our data suggest that acquisition of IgG1 antibody to MSA-119 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.
 

Key words: cerebral malaria, plasmodium falciparum, IgG antibody, adults, Sudan