Peroral vaccination with a temperature-sensitive mutant (HVJ-pB) of parainfluenza type 1 virus against respiratory tract infection

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The virulent strain of wild-type (wt) Sendai virus grows in the lung of mice when inoculated intranasally and causes viral pneumonia. However, no wt virus growth is found in the lung of mice inoculated perorally. A temperature-sensitive (ts) mutant derived from an Sendai virus carrier culture can multiply at 32ﾟC,but not at over 34ﾟC,and shows no pathogenicity to even newborn babies. Oral administration of the ts mutant induces mice a specific immune response and protects from pneumonia caused by the wt virus superinfection. Ultraviolet-irradiated ts mutant induces no protective immunity. A direct instillation of the ts mutant into the stomach through a tube is ineffective for a vaccination against the wt virus.These results indicates the ts mutant expresses viral proteins in oral mucous membrane and establishes mucosal immunity in the alimentary tract. By the common mucosal immune system mucous membrane in the respiratory tract also becomes immune from the wt virus challenge.