HLA-A*3306, a novel variant in the Indian population

Human leukocyte antigens in Indian patients with chronic myeloid leukemia

In chronic myeloid leukemia (CML), experimental studies using synthetic peptides identical to the bcr-abl fusion region have revealed the capability of specific peptides to bind to human leukocyte antigen (HLA) class I molecules (HLA-A2, A3, A11, B8) and class II molecules (HLA-DR1, DR2, DR3, DR4 and DR11). Individuals expressing HLA-A3, B8 or DR4 have a diminished risk for the development of CML in Caucasian populations. A statistically significant increase in the frequency of Cw3 and Cw4 antigens in Caucasians and European CML patients has been reported. However, HLA associations in CML have not been reported in India. In lieu of the allelic diversity of HLA in the Indian population, the present study assessed the possibility of an association of HLA molecules in Indian patients with CML. HLA A, B, C and DRB1 antigen associations in 180 clinically diagnosed Indian CML patients (aged 17 - 54 years) were analysed and compared with age-matched (n = 100) healthy individuals from the same ethnic background. In the HLA class I antigen distribution, a significant decrease was observed in HLA-A11 (25.6% versus 39%; P = 0.027, odds ratio (OR) = 0.54, 95% confidence interval (CI) = 0.31 - 0.94) and HLA-Cw6 (7.8% versus 20%; P = 0.005, OR = 0.34, 95% CI = 0.15 - 0.74). Among the DRB1 alleles, HLA-DRB1*13 (7.8% versus 17%; P = 0.031, OR = 0.41, 95% CI = 0.18 - 0.93) was decreased in CML patients. However, the differences for HLA-A11 (P(c) = 0.351) and DRB1*13 (P(c) = 0.403) did not remain significant after the application of a correction factor for the P-value. These results suggest that the development of CML is apparently associated with HLA phenotypes specific to each population and indicate that expression of HLA-Cw6 may result in a protective effect on CML acquisition in the Indian population.

Molecular diversity of HLA-Cw alleles in the Maratha community of Mumbai, Maharashtra, western India

Recent advances suggest a significant role for the HLA-C locus as a target of alloreactions after bone marrow transplantation. The biological importance of products of the HLA-C locus, both as transplant antigens and as ligands for natural killer (NK) cells, is well established. A total of 10 different serologically defined HLA-Cw antigen specificities (Cw1-Cw10) are encoded by the C locus; however, there are now 151 different alleles that can be identified by molecular methods. Serological definition of Cw alleles therefore includes 20-50% blanks, which cannot be detected by the available antisera. We used the molecular method of polymerase chain reaction (PCR)-based sequence-specific amplification and probe hybridization to define Cw alleles in 91 individuals from the Maratha community, and compared the data with data for 92 serologically typed Maratha individuals from India. We identified Cw*12, Cw*14, Cw*15, Cw*16 and Cw*18, along with the serologically identified Cw*01, Cw*02, Cw*03, Cw*04, Cw*06 and Cw*07 alleles. The HLA-Cw blank allele frequency in the Maratha was reduced from 0.5706 to 0.00. Furthermore, by using a molecular technique, it was possible to identify novel allele subtypes, such as Cw*0104, Cw*0203 and Cw*0707, and a high frequency of Cw* 1801 in the Maratha community compared with other Indian and world populations. Our results will have clinical implications in related and unrelated HLA-matched bone marrow transplantation in India.

HLA diversity among Nadars, a primitive Dravidian caste of South India

South India is one of the oldest geophysical regions mainly occupied by Dravidian language-speaking people. Here a random panel of 61 unrelated Nadar healthy individual from Tamil Nadu State were analyzed and compared with other populations of India and the world. HLA-A, B and C alleles frequencies and their haplotype frequencies were determined by high-resolution typing of genomic DNA. The analysis revealed that the Nadar caste of South India have several characters shared with East Asian populations consistent with the demographic history of South India, as well as specific features including several unique alleles such as A*03011, A*31011, B*15011, B*3501, B*51011, Cw*02022. In addition, haplotypes such as A*31011-Cw*02022-B*3501, A*03011-Cw*04011-B*4406 and A*2402101-Cw*04011-B*51011 are of high frequency in both these populations but are rare or absent in other populations of India and the world. The study suggests that a comparatively lesser degree of genetic admixture occurred between the South Indian and North Indian racial groups than that between South Indian and East Asian groups.

Molecular diversity of the HLA-A*19 group of alleles in North Indians: possible oriental influence

The present study aims to determine the genetic diversity of the HLA-A19 allelic family in the North Indian and Japanese populations. The HLA-A*19 group of alleles occurred at similar frequencies in North Indians and Japanese as in Caucasians. All the known serological splits of HLA-A19 were observed among the North Indians, i.e. A*33 (15.6%), A*32 (8.6%), A*31 (3.5%), A*30 (3%), A*29 (1.2%) and A*74 (0.77%), while only A*30 (0.7%), A*31 (17.6%) and A*33 (11.7%) were observed in the Japanese. High resolution analysis indicated that the A*29, A*30, A*31 and A*32 alleles were represented by only single subtypes among the North Indians while the HLA-A*33 group comprised two alleles, A*3301 (4.3%) and A*3303 (43.7%). All 15 of the HLA-A*33 positive samples from the Tamil population of South India were found to be A*3303. One novel subtype of A*33, A*3306 was also observed in the North Indian sample. Conversely, only one subtype each of A*30, A*31 and A*33 was encountered in the Japanese population, of which A*3101 and A*3303 were the most frequent (58.5% and 39%, respectively, among the HLA-A*19 group of alleles). All other subtypes of A19 were not found in the Japanese in the present study. The study suggests a significant amount of genetic admixture in the North Indian gene pool from other racial groups, with profound oriental influence.