CD4 and infection: Using a CCR5-tropic HIV-1 strain (able to infect both DCs and CD4+ T lymphocytes, unlike CXCR4-tropic strains, which do not infect DCs), it has been shown that transfer of HIV-1 from MDDCs occurs in a replication-independent mechanisms at first (in the first 20 h of co-culture with CD4+ T lymphocytes) and is taken over by a replication-dependent phase (cis-infection phase) partially relying on HIV replication in MDDCs (Turville et al., 2004).