Inhibition of human T-cell leukemia virus type I by the short oligoguanylic acids in vitro

The present study was undertaken to determine the inhibitory effects of several preparations of oligonucleotides for their anti-HTLV-I and HTLV-II abilities. Among them, the short oligoguanylic acids (oligo Gs), as short as three to four nucleotides in length, efficiently inhibited syncytium formation upon co-cultivation of MOLT-4 (clone 8) cells with HTLV-I-infected MT-2 cells or HTLV-II-infected Mo-T cells. No toxicity for the cells was detected with these compounds after 5 days of incubation, even at concentrations of up to 150 μM. The compounds also markedly blocked viral replication as assessed by reverse transcriptase of HTLV-I isolated from the culture supernatant of chronically infected MT-2 cells. Furthermore, oligo Gs also abolished the expression of HTLV-I p19 gag antigen in culture medium of MT-2 cells after one day of exposure. The inhibitory ability of oligo Gs in these experiments was shown to affect at least three steps in the life cycle of HTLV-I infection and these results further suggest that these new pharmacological agents may be developed for treatment of retroviral mediated diseases.