CD4 and infection: To improve the efficacy of this VOP, memory CD4+ T-cells of HIV+ART individuals were cultured in the presence or in the absence of ATRA, a stimulus demonstrated by our group and others to increase HIV replication either directly by increasing HIV transcription and/or indirectly by rendering neighboring cells highly permissive to infection (Cicala et al., 2009; Monteiro et al., 2011; Li et al., 2016; Gosselin et al., 2017).