The high degree of polymorphism of
human leukocyte antigen (HLA) genes has been suggested to result from natural selection against susceptibility to a variety of infectious pathogens, including
malaria. HLA molecules are considered to play a crucial role in the defense of the host against malarial
infection, and different HLA class I and class II alleles have been reported to be associated with reduced susceptibility to
malaria or the severity of
malaria in different populations. To test for associations between HLA alleles and the severity of
malaria in a Thai population, polymorphisms of
HLA-B and
HLA-DRB1 genes were investigated in 472 adult patients in northwest Thailand with
Plasmodium falciparum malaria. In this study,
malaria patients were classified into three groups: mild
malaria, non-cerebral severe
malaria, and
cerebral malaria. Our results revealed that the allele frequencies of
HLA-B46, -B56, and -DRB1*1001 were statistically different between non-cerebral severe
malaria and
cerebral malaria (P = 0.005), between mild
malaria and
cerebral malaria (P = 0.032), and between mild
malaria and non-
cerebral malaria (P = 0.007). However, our results may be showing false positives due to multiple testing. Thus, further study with a larger sample size must be conducted to obtain conclusive evidence of the association of these
HLA-B and DRB1 alleles with the severity of
malaria in Thailand.