The current study investigated the association between alleles of HLA-A, - B, -DR and DQB loci (genotypes and phenotypes) and Kala-azar disease in a sample of Iraqi patients. A total of 30 kala-azar patients was studied (12 males and 18 females). The mean age was 2.8 years (ranging between 5 months and 12 years). Blood samples were taken from each patient. In addition, blood samples were obtained from 20 age and sex matched apparently healthy controls. Blood samples were used for HLA-A, -B, -DR and DQB genotyping by polymerase chain reactionsequence specific primers (PCR-SSP). Statistical analysis was performed and P values were determined for each character. The result indicated that at HLA-class I region (HLA-A and HLA-B loci), some genotypes showed deviations (increased or decreased). However, none of
these deviations showed a significant variation. In patients, the most frequent HLA-A alleles were A*02010101-22, 24-33, 36-45, 47, 49-54, 57-61, 63, 64, 66-69, 71-77 , 79-86 and A*260101-0104, 03, 05, 0701-08, 10-12, 14-18, 21- 25N, 26. The most frequent HLA-B alleles were B*140201,0202,03,04,0601,0602 and B*510101, 0103, 0105-0107, 0201, 03, 08, 09, 11N, 1302, 14, 17, 18, 20, 26, 27N, 28-30, 32, 33, 35, 38 (20% for each). At HLA-class II region (HLA-DR and HLA-DQB loci), the frequency of DQB1*020101-0102,0202-04 genotype was significantly higher in patients (P=0.013), and it might play an important role in the predisposing to develop the disease. In contrast, the genotype DQB1*030302,030303,06,12,15 showed a decreased frequency in patients compared with controls (P=0.012). Furthermore, the genotype DR*150101-12, 14-16 was not detected in the patients, while it was
the most frequent genotype in control group (P=0.015). Therefore these two genotype might had some protective effect. At phenotypic level, ad at HLA-class I region, the total patients showed significant decreased frequency of A19 antigen (13.3 vs. 45%) as compared to controls, while at HLA-class II region, DR3 and DQB2 were significantly increased in patients (56 vs. 20% and 46.6 vs 10%, respectively) as compared to controls, and also they might played an important role in the predisposition to develop the disease. In contrast DR2 and DQB3 were significantly decreased in patients. In addition to that, Kala-azar disease was significantly associated with DR3-DQB2 (30 vs. 5 %) and DR2-DQB3 (0 vs. 10 %) haplotypes, suggesting that individuals with these allelic combinations had an increased risk to develop the disease, while the frequency of A19-DQB3 and A19-DR2 haplotypes was significantly lowered in patients compared to controls. In conclusion, these data suggested that some single HLA alleles and combinations were associated with a significant increased risk for Kala-azar disease. Thus, they may predispose individuals to develop this endemic parasitic disease.