Resumen de Una nueva estrategia para combatir la resistencia del hiv a los análogos de nucleosidos: inhibidores de la fosforolisis catalizada por la transcriptasa inverssa viral
UNA NUEVA ESTRATEGIA PARA COMBATIR LA RESISTENCIA DEL HIV A LOS ANÁLOGOS DE NUCLEOSIDOS: INHIBIDORES DE LA FOSFOROLISIS CATALIZADA POR LA TRANSCRIPTASA INVERSA VIRAL RESUMEN: in spite of the growing attention to the combined chemotherapy in the treatment of AIDS, the molecular mechanisms underlying the antiviral synergy of combinations of human immunodeficiency virus type 1 (Hiv-1) reverse transcriptase (RT) inhibitors are in most cases unknown. Most combinations of nonnucleoside inhibitors (NNRTI) with nucleoside analogues synergistically inhibit Hiv-1 replication in cell culture, though they fail to show synergy in enzymatic assays. We have examined the mechanisms mediating the synergy in combinations of azt with NNRTis on Hiv-1 RT and their possible relevance in antiretroviral therapy. Removal of 3'-azido-3'-deóxythymidine 5'-monophosphate (aztmp) from the terminated primer has been proposed as a relevant mechanism for the resistance of Hiv to 3'-azido-3'-deoxythymidine (azt). We found that non-nucleoside inhibitors (NNRTis) were able to inhibit the phosphorolytic activity of RT, rendering the azt-resistant RT sensitive to azttp. in addition, we described that the synergy found for combinations of NNRTis with azt is not due to the inhibition of the DNA polymerase activity, but to the inhibition of the phosphorolytic reaction by the nnrti. Our results also predict that any other inhibitor of the phosphorolytic activity, not only nnrtis, would enhance the effect of several nucleoside analogs, resulting in a more efficient therapy. Accordingly, we looked for new inhibitors of the phosphorolytic activity catalyzed by HIV-rt, mainly témplate/primer analogues and pyrophosphate analogues. 2-o-galloylpunicalin is a natural compound extracted from Terminalia triflora that behaved as a linear competitive inhibitor against primer/témplate. As expected, this compound inhibited the RT phosphorolytic activity and was synergistic when combined with azt. On the other hand, pamidroñate, a pyrophosphate analog, was also able to inhibit phosphorolysis, and therefore its combination with azt was also synergistic. Our results point out to the relevance of the inhibition of the phosphorolytical activity in the interaction between RT inhibitors. Taken together, these data can help to design new strategies for the development of more effective therapies.
