Abstract
Summary Alkaline hydrolysates of yeast ribonucleic acid were found to inhibit markedly plaque formation by vaccinia and chikungunya viruses in chick embryo fibroblast monolayers. Mononucleotides were subsequently implicated and shown to inhibit vaccinia virus plaque formation. Adenosine monophosphate was the most effective of the nucleotides tested in inhibiting vaccinia virus and the inhibition could be reversed with mixtures of the mononucleotides.