Pigeon paramyxovirus type 1 (PPMV-1) is an antigenic variant of Newcastle disease virus (NDV) which is mainly associated with infections of pigeons and has the potential to result in disease in chickens. In this study, we characterised 21 PPMV-1 isolates from diseased pigeons in China during 2007-2019. Phylogenetic analysis revealed that all isolates belonged to genotype VI. Among them, most isolates belonged to sub-genotype VI.2.1.1.2.2, suggesting that VI.2.1.1.2.2 has become a prevalent genotype in pigeons in China. The results showed that all PPMV-1 isolates were mesogenic in nature according to the mean death time (MDT) and intracerebral pathogenicity index (ICPI). In vitro and in vivo studies demonstrated that two genetically closely related isolates (Pi-11 and Pi-10) both of which belonged to sub-genotype VI.2.1.1.2.2 had similar replication kinetics in cells derived from pigeons, while the replication titre of Pi-11 was significantly higher than that of Pi-10 in cells derived from chickens. Pi-11 and Pi-10 could contribute to morbidity and mortality in pigeons. Remarkably, although the two viruses resulted in no apparent disease symptom in chickens, Pi-11 could cause more severe histopathological lesions and had a stronger replication ability in chickens compared to Pi-10. Moreover, chickens infected with Pi-11 had higher shedding efficiency than chickens infected with Pi-10. Additionally, several mutations within important functional regions of the fusion (F) and haemagglutinin-neuraminidase (HN) proteins might be associated with different pathogenicity of the two viruses in chickens. Collectively, these results indicated that the Pi-11-like virus of pigeon origin has the potential to induce severe outbreaks in chicken flocks. These findings will help us better understand the epidemiology and evolution of PPMV-1 in China and serve as a foundation for the further investigation of the mechanism underlying the pathogenic difference of PPMV-1 isolates in chickens.
Keywords: genotype VI; pathogenicity; phylogenetic analysis; pigeon paramyxovirus type 1.
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