Influence Of Haptoglobin Genotypes On Susceptibility To Malaria And The Effect Of Malaria Parasitemia To The Haptoglobin Levels In Children

ABSTRACT

Haptoglobin gene encodes for an acute phase protein; Haptoglobin and is expressed in three different polymorphic forms, Hp1-1, Hp1-2 and Hp2-2. Various studies on pathogenesis of Malaria maintain that Haptoglobin polymorphism influences host susceptibility to Plasmodium falciparum infection. A number of studies provide evidence that, individuals carrying Hp2-2 genotype are resistant to both Malaria infection and development of severe disease although some have shown that no influence manifested by the genotype. The present study aims on drawing clear information on the effect of the individual host Haptoglobin genotype to Malaria, focusing on the more Malaria susceptible group; Children under five years of age. The study also investigated how Plasma Haptoglobin level in the three Haptoglobin genotypes is affected by Malaria infection. A cohort of 344 under five years of age children in Morogoro was followed for an average of one year, where each child attended clinic once in every four weeks. Haptoglobin genotyping was done by PCR while was done by indirect ELISA. Among the 344 children, the proportion of the three genotypes (Hp1-1; Hp1-2; Hp2-2) was 85; 171; 88 and this obeys the Hardy-Weinberg equilibrium. Microscopic examination of blood smears found that positive cases for Malaria were 11.7%, 11.6% and 12.4% for the genotypes Hp1-1, Hp1-2 and Hp2-2 respectively. Haptoglobin levels were significantly higher with negative parasitemia when compared with Hp1-1 (p=0.01). The variation in the level of plasma Haptoglobin level due to Malaria infection was significantly higher in Hp2-2 when compared to Hp1-1 when compared by unpaired t-test (p=0.03). This study concluded that at the age below five years the Haptoglobin genetic polymorphism neither influences susceptibility to Malaria infection nor the disease development after infection and the magnitude of drop in plasma Haptoglobin level due to Malaria infection is higher in Hp2-2 than in Hp1-1 individuals.