Increased number of CCR5+ CD4 T cells among south Indian adults probably associated with the low frequency of X4 phenotype of HIV-1 in India.

BACKGROUND & OBJECTIVE: The shift of the human immunodeficiency virus (HIV) from nonsyncytium inducing strains (NSI/R5) to syncytium inducing strains (SI/X4) seen in subtype B infections during progression to acquired immunodeficiency syndrome (AIDS) is less frequently reported in subtype C. NSI and SI strains differ in the co-receptor they utilize to infect a T-cell. We postulated that a larger pool of CD4 T cells expressing CCR5 would be present among individuals in the Indian population. To validate this hypothesis, we estimated the percentage of CD4 cells expressing CCR5 or CXCR4 molecules among healthy south Indian adults and HIV infected individuals. METHODS: HIV-1 infected and uninfected adult volunteers, belonging to the four southern states of India with Tamil/Malayalam/Kannada or Telugu as their spoken language were prospectively recruited. A two colour flowcytometry examination of the blood sample was done using the following monoclonals; anti-CD45 (FITC)/CD14 (PE), anti IgG1 (FITC)/IgG2a (PE), anti-CD3 (FITC)/CD4 (PE), anti-CD3 (FITC)/CD8 (PE), anti-CD4 (FITC) and anti CCR5 (PE) or anti CXCR4 (PE). RESULTS: In the healthy population (n = 30) studied, 24.6 per cent of CD4 T cells expressed CCR5 and the percentage of CD4 T cells expressing CXCR4 was 80.4. Among the HIV infected individuals (n = 51) the percentage of CD4 T cells expressing CCR5 and CXCR4 was 26.8 and 78.7 per cent respectively. INTERPRETATION & CONCLUSION: The percentage of CD4 cells expressing CCR5 and CXCR4 in both the HIV uninfected and infected adults was significantly higher in the south Indian population than in the West. The larger pool of CCR5 positive CD4 cells probably allows for the R5 HIV strain to have a replication advantage over X4 HIV strains. This may explain the lack of shift in the viral phenotype during disease progression and also the perceived rapid progression of the disease in India compared to the West.