CD28 and HIV-1 infection: In line with the idea that a fraction of the host T cells of latent HIV-1 infection events had been rendered inert to TCR/CD3 activation, PMA/ionomycin stimulation of CD4+ T cell HIV-1 infected cultures consistently triggered higher levels of HIV-1 reactivation levels than antibody mediated CD3/CD28 stimulation (Fig 1A).