Objective:This study was undertaken to determine the contribution of HIV co-receptors and &bgr; chemokine secretion to the increased susceptibility for human immunodeficiency virus (HIV) infection of peripheral blood mononuclear cells (PBMC) obtained from HIV-seronegative Ethiopian immigrants in Israel (ETH).Study Design:Immune activation markers and HIV co-receptor expression on lymphocytes and monocytes, and &bgr; chemokine secretion by CD8+cells, were compared between ETH and non-Ethiopian Israeli (IS) HIV-negative individuals.Results:The percentage of lymphocytes and monocytes expressing CCR5 was 1.6 and 3.0 times higher in ETH (n= 83) than in IS (n= 45), respectively (P< .001), whereas RANTES and MIP-1&agr; secretion was 0.5 and 0.7 times lower (P< .01 andP< .05). The percentage of CCR5-expressing cells and RANTES secretion were inversely correlated (r = -0.7;P< .002). No differences were found in the proportion of CXCR4-expressing cells. No correlation between CCR5 expression and cell activation profile in the whole ETH population was found. However, in highly activated individuals (HLA-DR/CD3 >7%), a significant decrease in CCR5 expression was observed.Conclusions:An increased proportion of CCR5-expressing cells with decreased &bgr; chemokine secretion observed in ETH may account for the increased susceptibility to HIV infection of cells obtained from this group. These findings may partly explain the higher susceptibility for HIV infection in Africa and thus the rapid spread of acquired immunodeficiency syndrome (AIDS) in that continent.Journal of Human Virology 1999;2:283-289 © Lippincott Williams & Wilkins, Inc.