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Complement receptor 1 polymorphisms associated with resistance to severe malaria in Kenya.
Vandana Thathy1, JoAnn M Moulds, Bernard Guyah
1The US Army Medical Research Unit, The Kenya Medical Research Institute, Nairobi, Kenya. vthathy@wrp-ksm.org
Malaria Journal
|November 10, 2005
Summary
Certain blood group alleles, Sl2 and McCb, may offer protection against severe malaria. Specifically, the Sl2/2 genotype was linked to a reduced risk of cerebral malaria in Kenyan children.
Area of Science:
- Genetics and Human Evolution
- Immunology
- Tropical Medicine
Background:
- Complement receptor 1 (CR1) is a key immune molecule.
- African alleles Sl2 and McCb of CR1 (Swain-Langley and McCoy blood groups) are hypothesized to provide a survival advantage against Plasmodium falciparum malaria.
- Previous studies have not conclusively demonstrated this protective effect.
Purpose of the Study:
- To investigate the association between Swain-Langley (Sl) and McCoy (McC) blood group alleles and severe malaria outcomes in Kenyan children.
- To determine if specific Sl and McC genotypes confer a survival advantage in the context of malaria.
Main Methods:
- A case-control study was conducted in western Kenya.
- Children with severe malaria (cerebral malaria or anemia) were matched with uncomplicated malaria controls.
- Blood group alleles (Sl and McC) were genotyped using restriction fragment length polymorphism.
- Conditional logistic regression analysis was employed.
Main Results:
- No significant association was observed between Sl and McC alleles and severe malaria-associated anemia.
- Children with the Sl2/2 genotype showed a significantly lower likelihood of developing cerebral malaria compared to those with Sl1/1 (OR = 0.17).
- The Sl2/2 McC(a/b) genotype demonstrated a reduced risk for cerebral malaria compared to Sl1/1 McC(a/a) (OR = 0.18).
Conclusions:
- The findings support the hypothesis that the Sl2 allele, and potentially the McCb allele, evolved due to malaria transmission pressures.
- Specific combinations of Sl and McC alleles likely confer a survival advantage against severe malaria, particularly cerebral malaria, in endemic populations.