Antiviral efficacy of pyrazofurin against selected RNA viruses.

The antibiotic pyrazofurin, 3-(beta-D-ribofuranosyl)-4-hydroxypyrazole-5-carboxamide, markedly inhibited the in vitro replication of a number of RNA viruses including Rift Valley fever (RVF), Venezuelan equine encephalomyelitis (VEE), Sandfly, Pichinde, Lassa and LCM virus. Plaque formation was reduced by 80% or more with 2-10 micrograms/ml of pyrazofurin while 2 micrograms/ml reduced by 1000-fold the yield of Lassa and LCM virus in a yield reduction assay. In vivo, pyrazofurin failed to protect mice and guinea pigs against a lethal challenge with VEE and Pichinde virus, respectively.

Inhibition of RNA viruses in vitro and in Rift Valley fever-infected mice by didemnins A and B.

Didemnins, a new class of depsipeptides isolated from a Caribbean tunicate, have been shown to have potent antiviral activity against a broad range of RNA viruses in vitro. Didemnins A and B both protected mice against a lethal challenge of Rift Valley fever virus.

Effect of a nuclease-resistant derivative of polyriboinosinic-polyribocytidylic acid complex on yellow fever in rhesus monkeys (Macaca mulatta).

Rhesus monkeys (Macaca mulatta) treated with a newly developed nuclease-resistant complex of polyriboinosinic-polyribocytidylic acid, poly-L-lysine, and carboxymethylcellulose [poly (ICLC)] did not die after challenge with virulent Asibi strain yellow fever (YF) virus. The strain of virus is sensitive to the effects of interferon in vitro and is lethal for rhesus monkeys four to six days after subcutaneous administration of 1,000 plaque-forming units of the virus. The mortality rate was reduced in monkeys initially treated 8 hr before or after inoculation of virus but was unchanged in monkeys initially treated 24 hr after challenge.

Indirect mouse model for the evaluation of potential antiviral compounds: results with Venezuelan equine encephalomyelitis virus.

An indirect mouse model was utilized to evaluate the antiviral activity of several compounds against Venezuelan equine encephalomyelitis (VEE) virus infection in mice. Mice were given various dosages of lysine-stabilized polyriboinosinic acid-polyribocytidylic acid, a tilorone analogue, kethoxal, or mepacrine before and/or shortly after receiving one of several dose levels of attenuated strain TC-83 VEE virus. Twenty-one days later, the same mice were rechallenged intracranially with virulent Trinidad donkey strain VEE virus.

Evaluation of various analogues of tilorone hydrochloride against Venezuelan equine encephalitis virus in mice.

The antiviral activity of tilorone hydrochloride and three of its analogues (11,002, 11,567, and 11,877) was assessed by oral and intraperitoneal (i.p.) administration to Venezuelan equine encephalitis (VEE) virus-infected mice.