The in vivo inhibition by beta-phenylserine of rabies, myxoma, and vaccinia viruses.

The daily intraperitoneal administration of 19-15 mg of ,%phenylserine protected rats against death from lethal amounts of rabies virus. The protective effect was most marked when the animals were treated for 3 days prior to the injection of the virus, although initiation of treatment 24 hours after the virus was injected also gave protection. The administration of nn-phenylalanine or nn-tyrosine in combination with p-phenylserine reversed the inhibition of rabies virulence. Rabies-infected animals protected with /3-phenylserine and challenged with a second injection of rabies virus 6-7 weeks later did not show any immunity. The xanthine oxidase activity of infected rat brain increased during the course of rabies. The increased activity paralleled the titer of virus in the brain. There was no alteration in the xanthine oxidase activity when animals injected with the virus were treated with @-phenylserine. P-Phenylserine inhibited the propagation of vaccinia virus in rabbit skin when the compound and virus were mixed prior to injection. The daily intraperitoneal injection of 75 mg of p-phenylserine delayed the development of myxomatosis in rabbits. The compound had no apparent effect on the multiplication of influenza A (PRS), eastern equine encephalitis, poliovirus (Lansing strain), or mouse encephalomyelitis (FA strain) viruses in mice. The compound was inactive also against influenza A virus in embryonated eggs.