Selective toxicity of zindovudine for HIV is based on inhibition of

HIV binds to a surface molecule on CD4 lymphocytes and enters the cell, where viral RNA serves as a template for both positive and negative strands of complementary DNA. Reverse transcriptase (RNA-dependent DNA polymerase) transcribes the viral RNA. The double- stranded complementary DNA is then spliced into the host cell genome by a virus-encoded integrase. The mtegrated complementary DNA is then transcribed and translated into viral proteins. The dideoxy nucleosides including zidovudine, selectively inhibit revers transcriptase. Host cell DNA polymerase is more than 100 times less sensitive than the HIV polymerase to zidovudine.