CCR5 and HIV infectious disease: To examine bystander apoptosis in the absence of HIV infection, we microinjected 3000 U87-CD4-CCR5 cells into the cortex of mice containing astrocyte-specific deletion of Cx43, hGFAP-cre Cx43fl/fl, and control, Cx43fl/fl mice (with normal expression of Cx43) (Figure 1B).