Peroral vaccination with a temperature-sensitive mutant of parainfluenza virus type 1 protects mice against respiratory challenge infection.

Peroral vaccination for preventing respiratory infectious diseases was investigated in a murine model using a temperature-sensitive (ts) mutant of parainfluenza virus type 1. The ts mutant virus administered perorally in drinking water neither multiplied nor caused lesions in the respiratory tract or the central nervous system. However, ts virus antigen-positive cells appeared in oropharyngeal lymphoid tissues. This type of antigenic stimulation was capable of inducing both humoral and cellular immune responses, together with an augmentation of interferon production and natural killer cell activity, making it possible to protect the mice against challenge infection with a virulent wild-type virus. These results suggest that the oral cavity, a constituent member of the common mucosal immune system, is a candidate organ applicable as a vaccine route against virus respiratory diseases.