11th International AIDS Conference Vancouver, British Columbia — July 7-12, 1996

Int Conf AIDS 1996 Jul 7-12; 11:228 (abstract no. Tu.A.501)
Poli G, Ghezzi S, Alfano M, Vicenzi E; San Raffaele Scientific Institute, Milan, Italy. Fax: 39-2-2643-7989.

OBJECTIVE: To identify the mechanism of action of RANTES as an anti-HIV chemokine.

METHODS: T cell blasts from uninfected individuals were infected with eight primary HIV isolates in the presence or absence of RANTES (100ng/ml), and the cultures were monitored for the production of RT activity of p24 Ag production. MT-2 cells were used for determining the fusogenic abilities of different primary isolates. For HIV DNA PCR experiments, aliquots of infected blasts were harvested at different hours after infection. Two sets of primer pairs, detecting very early (minus strong stop DNA; primer pair R-U5) and nearly complete (U5-gag) HIV DNA were used.

RESULTS: RANTES consistently inhibited the replication of several primary HIV isolates in T cell blasts, although with different efficiency (range of inhibition: 40-97%). No correlation was observed between RANTES suppressive capacity and the in vitro viral phenotype (SI vs NSI). The suppressive effect of RANTES was observed in experimental conditions were cells were first infected for 1 h and then exposed to the chemokine, making it unlikely that RANTES inhibited the initial phases of receptor binding and entry into target cells. A more sustained effect of the chemokine was, however, frequently observed when blasts were pre-incubated with RANTES, and this experimental condition was used to investigate the step of reverse transcription. Two primary isolates that had previously shown complete and partial susceptibility, respectively, to the inhibitory effect of RANTES were selected. Complete and partial inhibition of reverse transcription was observed in T cells blasts after a single incubation with the chemokine. Inhibition or suppression of proviral DNA formation by RANTES involved also the synthesis of minus strong stop DNA.

CONCLUSIONS: RANTES is a potent suppressor of HIV replication which acts at an early step of the retrovirus life cycle, likely following entry into target cells and preceeding or directly interfering with the reverse transcription of the viral genome.

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TuA501

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