HLA-B35 frequency variations correlate with malaria infection in Sardinia

The hypothesis of a possible selective role of malaria in HLA. allele frequ ency Variations was investigated in Sardinia by typing completely 1,039 ind ividuals for HLA: 536 from six lowland villages exposed to malaria until 19 48, and 503 from six highland villages with no history of malaria. Another 1,928 individuals from 136 villages scattered all over the island were stud ied to establish if the HLA allele frequencies among villages correlated wi th the malaria incidence and/or altitude above sea level. Only correlated w ith the malaria incidence and/or altitude above sea level. Only the HLA-B35 allele yielded significantly higher frequencies in the Lowland versus the highland villages (P<1x10(-5)). The observed B35 Variance was 9.5 times hig her than expected in the absence of selection, showing an adaptive origin. The highly significant positive correlation found between HLA-B35 frequency and malaria in 136 villages suggests that malaria has been the selective f actor for HLA-B35 in Sardinia.