The increase in the relative frequency of CD4+ cells after 7 days coupled to the lack of possible recruitment of additional cells in an explant model suggests that the upregulation of the CD4 receptors on CD3+ cells not previously expressing CD4 could be a possible explanation for the increased HIV replication observed with MPA, since CD4 is also required for HIV-1 infection. Here, CD4 is linked to HIV-1 infection.