Abstract 1583 Neonatal Infectious Disease Platform, Monday, 5/3

Intracellular immunization of hematopoietic stem cells with anti-HIV genes may render the progeny cells (macrophages and lymphocytes) resistant to HIV. Human placental cord blood is rich in hematopoietic stem/progenitor cells. The capacity of stem cells to be infected with HIV is unclear. The chemokine receptors CCR5 and CXCR4 were recently identified as fusion coreceptors for macrophagetropic and T-cell tropic HIV strains respectively. With likelihood that cord blood stem cells will be used as targets for anti-HIV gene therapy, we investigated the expression of HIV receptors by cord blood-derived stem cells and their susceptibility to HIV infection in vitro. Highly purified CD34+ stem cells were isolated from placental cord blood of 7 healthy, term neonates using monoclonal antibody to the recently discovered AC133 antigen, the expression of which is restricted to CD34bright stem cells. CD34+ stem cells from cord blood contained mRNA for the major HIV receptor CD4, and for the HIV coreceptors CCR5 and CXCR4. However, cell surface expression of CD4, CCR5 and CXCR4 proteins could not be detected on stem cells by flow cytometry. Freshly isolated stem cells from cord blood were not susceptible to HIV infection as determined by reverse transcriptase assays and PCR for HIV DNA. In addition, inoculation with HIV did not affect the viability or differentiation of stem cells as determined by the number of colony-forming units-granulocytes/macrophages (CFU-GM) and CFU-megakaryocytes (CFU-Meg) derived from HIV-exposed stem cells, in comparison to stem cells not exposed to HIV. Cell surface expression of CD4, CCR5 and CXCR4 receptor proteins was detected on the progeny cells (macrophages and lymphocytes) derived from CD34+ stem cells after 2 weeks in culture and correlated with in vitro susceptibility of the progeny cells to HIV infection. These in vitro data suggest that freshly isolated CD34+ stem cells from cord blood are not susceptible to HIV infection and may not be reservoirs of HIV in the neonate. This may have important implications in designing stem cell-based therapeutic strategies for perinatal HIV infection, including those dealing with transduction of these cells with anti-HIV genes.

(Supported by 1UO1 AI 32921 and W.W. Smith Foundation)