Inhibition of vaccinia virus replication in skin of tuberculin-sensitized animals challenged with PPD.

Induction of a celayed-type hypersensitivity reaction in tuberculin-sensitized animals by tuberculin purified protein derivative (PPD) at the site of dermal vaccinia virus (VV) infection markedly accelerated elimination of VV and led to clinical recovery. Viral titers were depressed by over 99.9% in the skin of animals given PPD as compared to animals given phosphate-buffered saline or nonspecific irritants. Low concentrations of acid labile interferon were found in the skin of uninfected tuberculin-sensitized animals challenged with PPD. High concentrations of acid stable interferon were found in skin of tuberculin-sensitized animals infected with VV and challenged with either PPD or PBS. The time of appearance of the acid stable interferon was markedly accelerated, however, in the animals challenged with PPD as compared with PBS. It is concluded that recovery from dermal vaccinia infection can be enhanced by induction of a local delayed-type hypersensitivity reaction with an antigen untelated to the infecting virus.