INHIBITION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 INTEGRASE BY 3'-AZIDO-3'-DEOXYTHYMIDYLATE

The effects of 3'-azido-3'-deoxythymidine (AZT) and three of its intra cellular metabolites, azido- thymidine mono-, di-, and triphosphates, on the human immunodeficiency virus type 1 integrase have been determi ned. AZT mono-, di-, and triphosphate have an IC50 for integration bet ween 110 and 150 mu M, whereas AZT does not inhibit the integrase. The inhibition by AZT monophosphate can be partially reversed by coincuba tion with either thymidine monophosphate or 2',3'-dideoxythymidine mon ophosphate, suggesting that either of these monophosphates can bind to the integrase but that the azido group at the 3' position could be re sponsible for the inhibition, Integrase inhibition is associated with reduced enzyme-DNA binding but does not appear to be competitive with respect to the DNA substrate. Inhibition of an integrase deletion muta nt containing only amino acids 50-212 suggests that these nucleotides bind in the catalytic core, Concentrations up to 1 mM AZT monophosphat e can accumulate in vivo, indicating that integrase inhibition may con tribute to the antiviral effects of AZT. The increasing incidence of A ZT-resistant virus strains may, therefore, be associated with mutation s not only in the reverse transcriptase but also in the human immunode ficiency virus integrase. Finally, these observations suggest that add itional strategies for antiviral drug development could be based upon nucleotide analogs as inhibitors of human immunodeficiency virus integ rase.