Haplotypes and polymorphism in the CCR5 gene in sickle cell disease

Abstract

Sickle cell disease shows several clinical manifestations in distinct levels of severity. This heterogeneity is due to the haplotype variability associated with the HbS gene, levels of fetal hemoglobin and environmental conditions, which modify the disease expression. Science community believes that the presence of a polymorphism in the CCR5 gene, which is related to chronic inflammatory state, could confer a higher survival rate and a lower number of inflammatory events to these patients since the deletion in CCR5Δ32 would knock out the CCR5 gene. Therefore, this study aimed to identify the haplotypes in βS and βC genes, as well as to investigate the presence of the CCR5Δ32 deletion in patients with sickle cell disease. For this purpose, DNA was isolated with the QIAamp DNA Investigator Kit, and PCR was the method chosen to detect the mutant allele CCR5Δ32. The haplotypes in βS and βC genes were detected by RFLP with the restriction enzymes XmnI, HindIII, HincII, and HinfI analyzing six polymorphic sites on the β cluster, succeeded by electrophoresis. The atypical haplotype was the most common (54.3%), followed by Benin (28.6%), Bantu (11.5%), Senegal (2.8%), and Cameroon (2.8%). No patients presented CCR5Δ32 deletion. The increase in the frequency of atypical haplotypes suggests that these patients passed by variation in the genetic pattern from ancestral haplotypes throughout the years.