The first report of CCR5 delta 32 mutant in Thai injecting drug users.

CCR5, a chemokine receptor, is the principal coreceptor for macrophage-tropic HIV-1 which is the most important variant for viral transmission. It has been demonstrated that a homozygous genotype of a 32-bp deletion in CCR5 gene (delta32CCR5) shows a high degree of resistance to HIV-1 infection. To demonstrate that delta32CCR5 does exist in Thai natives, the CCR5 genotypes and allelic frequencies in 860 Thai injecting drug users (IDUs) were determined by PCR and DNA sequencing. Of these, six (0.7%) were CCR5/delta32CCR5 heterozygotes and no homozygote was found. The overall delta32CCR5 allelic frequency was 0.0035 and in HIV-1 seronegative (n = 490) and seropositive (n = 370) IDUs were 0.0051 and 0.0004, respectively, which were not significantly different (p = 0.3776). Here we report that the delta32CCR5 does exist in Thai IDUs as it is present in other human races. Such low allelic frequency may indicate that this mutation does not attribute a significant role in HIV-1 transmission in Thai IDUs.