In MDM infected with the CXCR4-tropic NL4.3, the percentage of cells in apoptosis progressively increased from day 4 up to day 10 post infection (43.5%) (time point at which the p24 production of the CXCR4-tropic NL4.3 becomes undetectable) and tended to remain stable at around 40% 13 days post infection (Figure 2). Here, CXCR4 is linked to infection.