Background:  DC-SIGN and DC-SIGNR efficiently bind and transmit HIV-1 to susceptible target cells in trans. Among the Caucasian population, we previously found that heterozygous DC-SIGN and DC-SIGNR 7/5 or homozygous DC-SIGNR 5/5 reduced the risk of HIV-1 infection in an exposed-seronegative cohort, while the homozygous DC-SIGNR 7/7 repeat is associated with an increased probability of HIV-1 transmission. Here we analyzed DC-SIGN/DC-SIGNR genotype and allele distribution among Han Chinese and compared them with those of the Caucasian population. 

Methods:  The studied cohort includes 520 healthy Chinese of Han ethnicity who were confirmed negative for hepatitis B virus (HBV), hepatitis C virus (HCV), and HIV-1. The cohort consists of 325 men and 194 women with an average age of 25. The DC-SIGN/DC-SIGNR repeat region was amplified by polymerase chain reaction (PCR) from genomic DNA extracted from peripheral blood mononuclear cells (PBMC), and alleles were distinguished by 3% agarose gel electrophoresis. Cloning and sequencing were performed to obtain sequences from allele 3 to 9. Fisher’s exact test was used for statistic analysis. The χ² test was used to estimate the difference of genotypes and alleles between the Chinese Han and Caucasian populations. Polymorphism information content of DC-SIGNR was calculated. 

Results:  Among the Han Chinese, we found 6 genotypes in the DC-SIGN repeat region based on number of repeats. Allele 7 was most common with a frequency of 0.9808. Alleles 4, 5, 6, and 8 with low frequency were also found, while only 3 alleles were identified in Caucasians:  allele 6, 7, and 8. Among Han Chinese, the DC-SIGNR genetic polymorphism frequency was high; its polymorphism information content was 0.5312. We identified 16 genotypes in the DC-SIGNR repeat region of Chinese Han individuals. Of these 16 genotypes, 8/5, 8/8, 9/4, 9/6, and 9/9 were not previously found in the Caucasian population. We observed a significant difference of 6/5, 7/4, 7/5, 7/6, 7/7, 9/5, 9/7, 9/9 genotype distribution and 5-, 6-, 7-, 9-allele frequency between the Chinese Han and Caucasian populations (p <0.01). More inserted mutation was found in Chinese Han than Caucasian population.

Conclusions:  DC-SIGN/DC-SIGNR genotypes and allele distribution among Han Chinese differs significantly from those among Caucasians, and exhibited unique genetic characteristics previously unrecognized in the Caucasian population，which may help find new polymorphisms related to HIV-1/AIDS transmission and progression