The Limited infectability by R5 HIV of CD34(+) cells from thymus, cord, and peripheral blood and bone marrow is explained by their ability to producebeta-chemokines

Objective. The resistance of human bone marrow (BM) CD34(+) cells to human immunodeficiency virus (HIV) infection is at this point not fully understoo d. Recently we reported that the chemokines MIP-1 alpha, MIP-1 beta, and RA NTES secreted by BM-derived CD34(+) cells may compete with the macrophagotr opic HIV (R5 HIV) strain for the CCR5 coreceptor. Materials and Methods. In this study we extended our previous observations and examined various lympho-hematopoietic CD34(+) cells isolated from thymu s (Th), cord blood (CB), mobilized peripheral blood (mPB), and BM for the e xpression of beta -chemokines binding to CCR5, i.e., MTP-1 alpha, MIP-1 bet a, RANTES, MCP-2, MCP-3, and MCP-4, and the alpha chemokine SDF-1 (binding to CXCR4) as these chemokines may compete with the R5 and X4 HIV strains, r espectively, far entry into cells. Results. We found that Th-, CB-, mPB-, and BM-derived CD34(+) cells express mRNA transcripts for all the beta -chemokines tested but not for SDF-1. Us ing sensitive ELISA assays we found that although MIP-1 alpha and MIP-1 bet a proteins were secreted by all the lympho-hematopoietic CD34(+) cells test ed, RANTES was detectable only in media conditioned by BM- and CB-derived C D34(+) cells and not Th-derived cells. However, media conditioned by BM-, m PB- and Th-derived CD34(+) cells protected the T lymphocytic cell line (PB- 1) from infection by the RS but not the X4 HIV strain. Conclusions. Hence this study demonstrates that beta -chemokines are secret ed by lymphohematopoietic CD34(+) cells originating from various sources an d that these endogenously secreted chemokines may limit entry of the R5 HN strain into the cells by competing for the CCR5 coreceptor. (C) 2000 Intern ational Society for Experimental Hematology. Published by Elsevier Science Inc.