Development and Biological Properties of a New Live Attenuated Mumps Vaccine Strain

<b>Background/Objectives</b>: This study aimed to develop a new attenuated live mumps vaccine strain and determine its biological properties and effectiveness. <b>Methods</b>: Plaque purification and amplification were performed in chicken embryo cells. Candidate live attenuated mumps MuV-365 strain sequencing was performed. After evaluating the potential neurotoxicity of the MuV-365 mumps strain, a preclinical safety evaluation of measles-mumps-rubella (MMR) live attenuated vaccine containing the MuV-365 strain was performed to support the registration and application of the MMR vaccine. Finally, mumps neutralization antibody titers and the concentration of anti-serum mumps-specific IgG were determined to evaluate the immunogenicity and efficacy of the MuV-365 strain and MMR vaccine in mice and rhesus monkeys. <b>Results</b>: The plaque of the PL-KUM main seed virus was screened, and strains whose sequences were highly homologous to RIT4385 (JL-5 derived) were selected to amplify. The candidate live attenuated mumps MuV-365 strain was then developed. Safety evaluation results indicated that the MuV-365 strain had no potential neurotoxicity, and the MMR vaccine containing the MuV-365 strain also showed no significant safety hazard. The immunogenicity of MuV-365 strain in BALB/c mice was not inferior to S79 and PL-KUM. After two doses of the MuV-365 strain, the concentration of anti-serum mumps-specific IgG of the MuV-365 strain was significantly higher than that of the S79 strain (<i>p</i> < 0.01). In rhesus monkeys, the MMR vaccine had good immunogenicity against measles and rubella after one dose, while immunogenicity against mumps improved after two doses. <b>Conclusions</b>: The developed MuV-365 strain was genetically stable, with adequate safety and immunogenicity.