Features of KIR gene polymorphisms in unpaid blood donors with occult hepatitis B infection

Objective To investigate the KIR gene polymorphisms and their features in unpaid blood donors with occult hepatitis B infection(OBI). Methods A total of 105 unpaid blood donors with OBI were screened out from the unpaid blood donors in Chongqing Blood Center from 2016 to 2019. Peripheral blood samples were collected for DNA extraction and KIR genotyping. KIR genotype ID and haplotype were determined based on a comparative analysis of the KIR genotype database published on the international allele website. Genotype frequency was calculated according to the equation of genotype frequency( F) = ,in which f represented the proportion of a phenotype of KIR gene. The chi-square test was used for comparison of categorical data between groups. Results All 105 OBI blood donors had the KIR genes 2 DL4,3 DL2,3 DL3,and pseudogene 3 DP1. The KIR genes 2 DL1,2 DL3,3 DL1,2 DS4,and pseudogene 2 DP1 had an F value of > 70%,among which the KIR gene 2 DS4 with exon 5 deletion had an F value of 26. 32%. The KIR genes with low frequency(< 30%)were 2 DL2,2 DL5,2 DS1,2 DS2,2 DS3,2 DS5,and 3 DS1. Compared with the Han population in Chongqing,Hebei,and Jiangsu and the Tibetan population in Lasa,the OBI blood donors had a significantly lower frequency of the KIR 2 DL3 gene(χ~2= 9. 598,12. 236,13. 719,and 10. 974,all P < 0. 05). There were significant differences in the frequencies of 2 DL2,2 DL5,2 DS2,and 2 DS3 between the OBI blood donors and the Uyghur population in Urumqi(χ~2= 16. 215,6. 981,19. 498,and 11. 819,all P < 0. 05). There were significant differences in the frequencies of 2 DL2,2 DS1,2 DS2,2 DS3,and 2 DS4 between the OBI blood donors and the Caucasians(χ~2= 22. 477,3. 877,34. 937,6. 909,and 4. 271,all P < 0. 05). Compared with the Han population in Chongqing,the OBI blood donors had a significant increase in the frequency of KIR 2 DS4* del(χ~2= 12. 911,P < 0. 05). Compared with the population with chronic HBV infection,the OBIblood donors had significant reductions in the frequencies of 2 DS2 and 2 DS3(χ~2= 13. 005 and 8. 289,P < 0. 05) and significant increases in the frequencies of 2 DS4 and 3 DL1(χ~2= 10. 032 and 3. 865,P < 0. 05). Compared with the population with ankylosing spondylitis,the OBI blood donors had significant reductions in the frequencies of 2 DL3 and 2 DS3(χ~2= 7. 851 and 16. 504,P < 0. 05). Compared with the gays with HIV-AIDS,the OBI blood donors had significant increases in the frequencies of 2 DS4 and 3 DL1(χ~2= 15. 491 and 4. 475,P <0. 05). There were significant differences in the frequencies of 2 DL1,2 DL2,2 DL3,2 DL4,2 DL5,2 DS4,3 DL2,3 DL3,and 2 DP1 between the OBI blood donors and the population with sporadic acute hepatitis E(χ~2= 4. 448,30. 934,17. 942,15. 638,4. 227,13. 802,32. 667,35. 653,and 36. 566,P < 0. 05). A total of 21 KIR genotypes were found,among which genotype AA1 had the highest frequency of 49. 52%,followed by genotype Bx2(18. 1%). Conclusion OBI blood donors have unique features of KIR gene polymorphisms. KIR2 DL3 is a potential protective gene for OBI,while KIR 2 DS4 * del is a potential susceptibility gene for OBI.