Studies On The Distribution Of The Allotypic Variants Of The Igg Receptors (Fcyriia And Fcyrihb) And Their Association With Severe Clinical Malaria Among Ghanaian Children

ABSTRACT

The immunoglobulin G (IgG) receptors FcyRIIa and FcyRIIIb vary among different

ethnic groups, and more importantly, are also known to be associated with either

susceptibility to or protection from certain diseases. These variations are manifest as

differences in the antigen-binding capabilities of the receptors. The genes encoding

for these receptors are polymorphic and these also vary among populations. These

variations can be investigated using molecular methods such as PCR. The aim of the

present study was to determine if there were any significant differences in the

distribution of these genotypes among some of the ethnic groups in Ghana and also if

there was any association between the genotypes and the incidence of severe malaria.

A total number of 329 children, belonging to four different tribes were recruited for

the study, of which 75 healthy individuals formed the control group. The 254

patients who were recruited were diagnosed as having uncomplicated, severe

anaemia or cerebral malaria. Human DNA was isolated from filter paper blood blots

for PCR analysis using allele-specific primers for FcyRIIa to detect H/H131,

H/R131, R/R131, and FcyRIIIb to detect NA1/NA1 and NA2/NA2 genotypes.

The results obtained revealed that there was no association between ethnicity and the

FcyRIIa genotype, (P=0.78) and FcyRIIIb genotypes (P=0.23). W ith regard to the

incidence of malaria and the FcyRIIa genotypes, the following associations were

found (P0.05.

The homozygous NA1/NA1 was found to be significantly dominant among the

patient group (P=0.003). The NA2/NA2 genotype on the other hand was

significantly reduced in the patient group (P=0.000), and also in all the three forms of

the diseases (P< 0.04). The heterozygous NA1/NA2 was found to be intermediate

between the two, but was significantly underepresented in the cerebral and severe

anaemia patients (P< 0.001). The null genotype was found to be overepresented

within the patient group (P=0.02).

These findings suggest that the NA2 offers protection against all forms of malaria

and this effect is even observed in the heterozygotes NA1/NA2 among the severe

anaemia and cerebral malaria groups. NA1, on the other hand is a heritable

predisposing factor to symptomatic malaria.