Effect of the extent of thiolation and introduction of phosphorothioate internucleotide linkages on the anti-HIV activity of Suligovir [(s4dU)35].

Suligovir is a 35-mer homo-oligonucleotide, containing exclusively 4-thio deoxyuridylate, proved to be a potent inhibitor of HIV entry. In this paper, we described the effect of extent of thiolation and the introduction of nuclease-resistant phosphorothioate linkages on the anti-HIV activity of Suligovir. We found that the decreased thiolated nucleotide content decreases the anti-HIV potency of the compound and the introduction of phosphorothioate linkages does not improve its antiviral activity.

Potent inhibition of HIV-1 entry by (s4dU)35.

We have previously reported the potent in vitro HIV-1 anti-reverse transcriptase activity of a 35-mer of 4-thio-deoxyuridylate [(s(4)dU)(35)]. In efforts to define its activity in a more physiological system, studies were carried out to determine the stage of viral infection that this compound mediates its anti-viral effect. Results of the studies reported herein show that (s(4)dU)(35) is nontoxic and is capable of inhibiting both single and multi-drug resistant HIV strains (IC(50): 0.8-25.4 microg/ml) in vitro. Besides its previously reported anti-RT activity, (s(4)dU)(35) mediated its antiviral action by preventing virus attachment (IC(50): 0.002-0.003 microg/ml), and was stable in vitro and slowly degraded by DNAses. Competition studies and fluorescence resonance energy transfer (FRET) experiments indicated that (s(4)dU)(35) preferentially binds to CD4 receptors, but not to CD48. Confocal laser scanning microscopy (CLSM) studies showed that (s(4)dU)(35) did not penetrate into the cells and colocalized with cell surface thioredoxin. Our studies identify (s(4)dU)(35) as a potential novel HIV entry inhibitor that may have utility as either a systemic antiretroviral or as a preventing agent for HIV transmission.

Effect of increasing thiolation of the polycytidylic acid strand of poly I:poly C on the alpha, beta and gamma interferon-inducing properties, antiviral and antiproliferative activities.

Double-stranded RNAs induce interferons and cause the development of antiviral and antiproliferative activities. Antiviral activity is related to the production of interferons and other proteins that stimulate various immunologic activities, which appear to contribute to their overall antiproliferative activity. The most active double-stranded RNA, polyI:polyC, was shown to be too toxic for therapeutic use. We conducted selective thiolation of the polyC strand at the five position of the cytosine bases, generating a partially thiolated polyC (MPC) which after annealing with a complimentary unmodified polyI, gave the thiolated double-stranded RNA, pI:MPC. We have explored antiviral and antiproliferative activities at various levels of thiolation and found that optimal responses can be obtained at 7.4% level of thiolation. This compound deserves further study of antiviral and antiproliferative responses in vivo, and eventually clinical exploration. Earlier studies have shown that this and related compounds are active against HIV-1, in human cells, and against DNA polymerases of DNA and RNA tumor viruses.

New approaches to the treatment of AIDS with special reference to overcoming interferon resistance.

This is a brief review on studies of attacking HIV through a new angle. In previous studies, we have found that many patients with AIDS are resistant to interferon (IFN) therapy, and some develop resistance during therapy. Four factors were found to be responsible for the resistance of untreated patients: (a). release of free-circulating IFN-alpha/beta type 1 receptors, (b). a newly detected IFN inhibitory protein, (c). high prostaglandin E2, and (d). high levels of cAMP phosphodiesterases, particularly in AIDS-related neoplasms. This may interfere with intrinsic disease resistance and with the efficacy of IFN therapy. In an attempt to overcome this resistance, new compounds were synthesized which increase endogenous production of alpha, beta and gamma IFNs, have anti-template activity against DNA and RNA polymerases, inhibit reverse transcriptases and activates IFN-induced double-stranded RNA (dsRNA)-dependent protein kinase. It is expected that planned nonhuman primate and clinical studies will support preliminary findings. Preliminary in vitro and animal studies suggest that these new compounds may be effective against HIV, including multi-drug resistant strains.