Is resistance to P. falciparum infection in sickle cell trait (AS) individuals is related to presence of high frequencies of haptoglobin Hp2-1?

Abstract

Sickle cell anemia is a haemoglobinpathy due to a single point mutation in the -chain of human haemoglobin. A hospital based case control study was done on the paediatric section in Khartoum Teaching hospital to investigate the role of haptoglobin phenotypes among sickle cell disease patients. A total number of 127 sickle disease patients and 34 healthy controls were screened for Hb phenotypes. Out of 88 homozygous sickle cell anaemia patients (HbSS), 77.3% patients had the Hp 1-1 phenotype, 22.7% had the Hp 2-1 phenotype, and none of them had Hp 2-2 type. Out of the 39 sickle cell trait (HbAS) individuals, 41% individuals had Hp1-1 phenotype, 59% had Hp21 phenotype and none of them had the Hp 2-2 phenotypes. Out of the 34 healthy controls (HbAA), 44% had Hp 1-1 phenotype, 38% had Hp 2-1 phenotype and 18% had Hp2-2 phenotype. There was a highly significant difference in the distribution of haptoglobin phenotypes among the three groups (P = 0.0001). The sickle cell trait (AS) had high frequency of Hp2-1. The sickle cell disease individuals (SS) had higher frequencies of Hp1-1. In conclusion, Malaria infection among the sickle cell homozygous (SS) individuals may be related to the high frequency of Hp1-1 and the protection of sickle cell trait (AS) against malaria infection may be due to the high frequency of haptoglobin phenotype 2-1.