Attenuation of bovine parainfluenza virus type 3 in nonhuman primates and its ability to confer immunity to human parainfluenza virus type 3 challenge.

Bovine parainfluenza virus type 3 (PIV-3) was evaluated as a candidate live-virus vaccine to protect against infection with human PIV-3. The level of replication of bovine and human PIV-3 and the efficacy of immunization with bovine PIV-3 in protecting against subsequent challenge with human PIV-3 was evaluated in nonhuman primates. The duration and magnitude of replication of human and bovine PIV-3 in the upper and lower respiratory tracts of New World monkeys was similar, and animals infected with bovine PIV-3 developed resistance to challenge with human PIV-3. The replication of two bovine strains of PIV-3 was restricted 100- to 1000-fold in Old World primates but was sufficient to induce high levels of neutralizing antibody to human PIV-3. The combined properties of restricted replication and induction of a protective immune response to human PIV-3 in nonhuman primates make bovine PIV-3 a promising candidate for a live-virus vaccine to protect humans against disease caused by PIV-3.