Avian paramyxovirus Type 1 from wild birds: population adaptation and immunogenicity in chickens

Authors: ESPEJO, RAIMUNDO - Auburn University; Goraichuk, Iryna; Suarez, David; BREEDLOVE, CASSANDRA - Auburn University; TORO, HAROLDO - Auburn University

Submitted to: Avian Diseases
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/21/2025
Publication Date: 9/23/2025
Citation: Espejo, R., Goraichuk, I., Suarez, D.L., Breedlove, C., Toro, H. 2025. Avian paramyxovirus Type 1 from wild birds: population adaptation and immunogenicity in chickens. Avian Diseases. 69 (3): 243–251. https://doi.org/10.1637/aviandiseases-D-25-00026.
DOI: https://doi.org/10.1637/aviandiseases-D-25-00026

Interpretive Summary: Newcastle disease virus (NDV) causes a serious disease in chickens and turkeys that can result in rapid transmission and high mortality in naive animals. Because of the threat of infection, there is widespread use of vaccination for control. Although the virus is an RNA virus that changes over time, currently NDV is considered to be a single serotype meaning that vaccines made from one virus should protect for all ND viruses. However, the closer the vaccine strain is to the circulating virulent virus, the better protection is observed. Currently most vaccines are based on the LaSota strain of virus, which has many changes that may limit it's optimal protection. This study compared several genetically diverse low virulent strains of NDV that could potentially be developed into vaccines. Because these viruses came from wild birds, the goal was to adapt these viruses to grow better in embryonating chicken eggs, which is how vaccine viruses are normally grown. The four viruses tested could be adapted to high growth in eggs and several of these viruses produced good antibody titers in day old chickens without causing clinical disease. Therefore these viruses may be possible alternative vaccine strains and further work needs to be done.

Technical Abstract: We examined the replication and adaptation of avian paramyxoviruses serotype 1 (APMV-1) Mallard/US(OH)/04-411/2004, Northern pintail/US(OH)/87-486/1987, Mottled duck/US(TX)/TX01-130/2001, and Mallard/US(MN)/MN00-39/2000, and assessed their potential as vaccine candidates for chickens. The adaptability of each virus was examined by serial passage in embryonated chicken eggs (ECE) and in Vero cells. All APMVs successfully replicated in ECE. In contrast, two isolates passaged in Vero cells showed successful replication and two showed a continuous decline in viral load during passages. Whole genome sequencing analysis identified 14 genomic positions with significant in mean allele frequency. Changes of the predominant virus population were characterized by shifts of amino acid frequency at seven positions. Notably, four of these changes were located in the HN protein and three were found in the L protein. Remarkably, while the percentage of alternative amino acids in viral populations passaged in ECE showed limited variation, e.g., at aa position 126 of HN, the frequency varied from 7.4% to 19.8% and HN aa position 253 from 12.1% to 22.5%, the variation of the viral populations passaged in Vero cells was significantly higher at the same positions (e.g. the frequency of the alternative amino acids at HN aa positions 126 and 253 changed from 20.8% to 95.2% and 24.1% to 93%, respectively). Isolate 2 passaged in Vero cells displayed a marked variation in alternative amino acid frequencies, specifically at positions 126 and 253 within the HN gene. Isolate 3, while showing no alterations at the same HN positions, showed a considerable change in alternative amino acid frequency in the L protein at position 4132, a change occurring only in the Vero cell environment. One-day-old SPF chickens inoculated with isolates passaged in ECE elicited serum antibody responses similar to those elicited by the LaSota reference strain. In contrast, APMVs passaged in Vero cells showed limited replication in chickens and reduced induction of systemic antibody. Interestingly, one virus passaged in ECE and another in Vero cells elicited IgA levels in lacrimal fluid comparable to the LaSota strain. We concluded that the four wild-bird APMV isolates tested demonstrated successful adaptation to ECE, with one isolate eliciting overall immune responses comparable to the LaSota virus, supporting their potential as vaccine candidates.