Size and stability of a naturally occurring virus inhibitor

We recently described a virus inhibitor (contact-blocking virus inhibitor) which was produced spontaneously by untransformed human and murine cells in tissue culture (S. Baron and L. McKerlie , Infect. Immun . 32:449-453, 1981). This contact-blocking virus inhibitor was characterized by broad antiviral activity, high potency, and reversible inhibition of viral attachment. Unlike interferon, the antiviral activity of the contact-blocking virus inhibitor is not species specific. An inhibitor with similar properties can also be demonstrated in many body fluids and surface secretions. We report here studies on the stability of the antiviral species which indicate that it is resistant to denaturation by heat (100 degrees C), acid (pH 2), and alkali (pH 12). The antiviral activity against all viruses tested resides in a low-molecular-weight molecule. The range of characteristics so far determined for the contact-blocking virus inhibitor distinguishes it from other virus inhibitors reported in the literature.