Development and applications of an inactivated pigeon paramyxovirus type I in which the F gene was replaced with the LaSota F gene.

No specific vaccine against pigeon paramyxovirus type I (PPMV-I) exists. Newcastle disease (ND) vaccines developed for other poultry has unsatisfactory efficacy against PPMV-I. We aimed to develop an effective PPMV-I vaccine by constructing an inactive, recombinant WT (rWT) PPMV-I strain. In phylogenetic analysis, the Pi/WT/2016 (WT) strain PPMV-I was a subgenotype VI.2.1.1.2.2 (VIk) of Class II Newcastle disease viruses (NDV), closely related to the NX/2068/2016/Pi (MG840654.1) strain, but genetically distant from the chicken-origin LaSota strain on which the commercial ND vaccine is based. The whole-genome sequence of the WT strain revealed a moderate virulence-related 112RRQKRF117 cleavage site, which is not suitable as a vaccine candidate. Using reverse genetics, we exchanged the WT strain fusion protein (F) gene with that of LaSota to construct an rWT strain as a candidate vaccine strain. This resulted in significant virulence reduction while preserving immunogenicity. The rWT-based vaccine elicited a stronger humoral immune response in pigeons than the LaSota strain-based vaccine. In animal experiments, the immunity duration of the vaccine could last up to 13 months. Antibody levels in the parent pigeon exceeded 10 log2, and maternal antibody levels in the offspring reached high levels within 21 days. Thus, our inactivated rWT-based vaccine exhibits ideal immunogenicity and protective effects, providing a promising strategy for further development of inactivated vaccines against PPMV-I.