FIG 4.

(A) NRTI thymidine analog antiviral activity is inhibited by exogenous addition of thymidine in MDM. Thymidine (1 mM) was added to the culture medium together with the corresponding drug 4 h prior to infection with VSV-pseudotyped HIV-1 GFP virus, and replication was assessed 2 days later. Means ± SD from two independent donors performed in duplicate are shown. (B) Intracellular dNTP levels in MDM treated with exogenous addition of dThD. dThD (1 mM) was added to the culture medium for 24 h before dNTPs were extracted and measured. Means ± SD from three independent donors are shown. (C) NRTI cytidine analog antiviral activity is inhibited by exogenous addition of cytidine in MDM. Cytidine (1 mM) was added to the culture medium together with the corresponding drug 4 h prior to infection with VSV-pseudotyped HIV-1 GFP virus, and replication was assessed 2 days later. Means ± SD from two independent donors performed in duplicate are shown. (D) Intracellular dNTP levels in MDM treated with exogenous addition of dCtD. dCtD (1 mM) was added to the culture medium for 24 h before dNTPs were extracted and measured. A representative experiment is shown. dThD, deoxythymidine; dCtd, deoxycytidine; ND, no drug. *, P < 0.05; **, P < 0.005.