A new subtype of a natural viral inhibitor (CVI) that is stable in the gastrointestinal tract.

A virus inhibitor found in gastric secretions and in extracts from gastrointestinal tissues is described. The inhibitor shares a number of characteristics with the recently described contact-blocking virus inhibitor (CVI), which is produced by unstimulated cells in culture, and occurs naturally in some body fluids. The new inhibitor, which we have designated gastrointestinal-CVI (GI-CVI) is similar to the originally described CVI in its resistance to denaturation by acid and alkali, stability at 100 degrees C, and broad antiviral action. GI-CVI can be distinguished from the previously described material by its resistance to proteolytic inactivation and enhanced heat stability, however. This new virus inhibitor has been found in significant titers in gastrointestinal secretions and tissue extracts from three mammalian species.