The recombinant chimeric human parainfluenza virus type 1 vaccine candidate, rHPIV3-1cp45, is attenuated, immunogenic, and protective in African green monkeys

A recombinant live-attenuated chimeric human parainfluenza virus type 1 (HPIV1) candidate vaccine was previously generated by replacing the fusion (F) and hemagglutinin-neuraminidase (HN) glycoprotein open reading frames (ORFs) of the HPIV3 candidate vaccine, rHPIV3 cp 45, with those of wild-type HPIV1. Previously, this recombinant chimeric virus, designated rHPIV3–1 cp 45, exhibited a greater level of the temperature sensitivity of replication in vitro and a greater level of attenuation of replication in the respiratory tract of immunized hamsters when compared to its HPIV3 cp 45 parent virus. In the present study, rHPIV3–1 cp 45 was evaluated for its level of attenuation and efficacy in African green monkeys ( Cercopithecus aethiops ), a primate in which both HPIV1 and HPIV3 wild-type viruses replicate efficiently. The rHPIV3–1 cp 45 candidate vaccine was as restricted in replication in the upper and lower respiratory tract as its thoroughly characterized rHPIV3 cp 45 parent indicating that the attenuating mutations present in the rHPIV3 cp 45 backbone specified an appropriate level of attenuation of rHPIV3–1 cp 45 for primates. The level to which rHPIV3–1 cp 45 replicated in the respiratory tract of African green monkeys was also sufficient to induce a strong immune response to HPIV1 and provided protection against challenge with wild-type HPIV1. These results provide a basis for further evaluation of this HPIV1 candidate vaccine in humans.