Experimental infection of avian paramyxoviruses in chickens and mice

Avian paramyxoviruses (APMVs) are being increasingly detected in wild birds, yet the pathogenic potential of novel species remains poorly defined. We characterized the molecular determinants and pathogenicity profiles of seven APMV strains. Sequence analyses identified conserved hemagglutinin-neuraminidase (HN) receptor-binding and V protein immune-modulatory motifs, whereas F cytoplasmic-tail motifs, P and W trafficking signals, and L methyltransferase motifs were strain-specific. In day-old chicks, all strains showed low-pathogenic phenotypes, but APMV-1 class II, a wild-bird-origin strain developed and commercialized as a Newcastle disease vaccine strain, exhibited broader tissue distribution, oral and cloacal shedding, lung cytokine induction, and hemagglutination inhibition (HI) seroconversion. Other APMVs showed restricted replication, characterized mainly by oropharyngeal shedding, limited lower respiratory tract involvement, and no detectable serum HI response. In BALB/c mice, viral RNA was detected predominantly in respiratory tissues; APMV-13 and APMV-14 were associated with mild body weight loss. Cytokine responses in the lung and spleen varied among APMVs, while HI seroconversion was detected in mice inoculated with APMV-1 class I, APMV-14, and APMV-16. These results highlight strain-specific infection profiles, with APMV-1 class II exhibiting greater adaptation to chickens, whereas the other tested APMVs caused subclinical infections and induced variable immune responses in mice.