Immunogenicity and protection efficacy evaluation of avian paramyxovirus serotype-1 (APMV-1) isolates in experimentally infected chickens

Abstract

Vaccine failures after Newcastle disease vaccination with the current commercial vaccines have been reported and are associated with many factors, including genotypic and antigenic differences between vaccine and outbreak strains, although all APMV-1 members belong to one serotype. We assessed the immunoprotection ability of four thermostable, low-virulent Newcastle disease-virus isolates from Ugandan waterfowl against challenge with a virulent strain (MDT = 36.8 h, ICPI = 1.78) isolated from morbid chicken. Six-week-old commercial Leghorn layers, challenged at 21 days post immunization were used. Four isolates designated: NDV-133/UG/MU/2011, NDV-177/UG/MU/2011, NDV-178/UG/MU/2011 and NDV-173/UG/MU/2011 induced mean haemagglutinin inhibition antibody titres of log 9.3, 8.2, 6.3 and 2.0, respectively, at 21 days post immunization. The antibody titres correlated with the protection rates (R² = 0.86, p < 0.007) of 60%, 50%, 20% and 0% of birds, respectively, against challenge at 14 days post challenge. Further evaluation of these and more low-virulent isolates might provide an alternative to the current commercial vaccine failures.

Epitope Peptide-Based Predication and Other Functional Regions of Antigenic F and HN Proteins of Waterfowl and Poultry Avian Avulavirus Serotype-1 Isolates From Uganda

“…However, our previously reported vaccination results in Omony et al (35) did not fully prevent ND infection under our experimental conditions where we used four avirulent NDV isolates from waterfowl as vaccine strains and challenged the immunized birds with a virulent NDV isolates from poultry. In any case, excretion of the challenge virus might have occurred.…”

“…The presence of avirulent ND viruses in waterfowl indicates that wild birds may be a potential source of virulent AAvV-1 for poultry due to possible point mutations at FPCS (7,48). At the same time, these wild birds might therefore serve as a source of potential vaccine isolates (35). Conservation of F and HN proteins at N-glycosylation, cysteine sites, and other specific structural and functional sites like receptor (sialic acid) binding sites between AAvV-1 isolates from waterfowl and poultry together with vaccine strains indicate these are required for biological active state especially among amino acids residues involved at the direct interactions that form a high-level structural integrity (49,50).…”

“…The presence of avirulent ND viruses in waterfowl indicates that wild birds may be a potential source of virulent AAvV-1 for poultry due to possible point mutations at FPCS ( 7 , 48 ). At the same time, these wild birds might therefore serve as a source of potential vaccine isolates ( 35 ).…”

“…The positive samples were also biologically characterized using standard pathogenicity tests (mean death time, intracerebral pathogenicity test, and intravenous pathogenicity test described by 33). In vivo evaluation of immunogenicity and protection efficacy on four of these AAvV-1 isolates was performed previously as described in Omony et al ( 35 ). These waterfowl AAvV-1 isolates were sequenced for partial F gene targeting the cleavage site and the hypervariable region of the F gene.…”

“…Recently, we isolated thermostable, low-virulent ND viruses in waterfowl and compared their immunogenicity with those of the vaccine (LaSota and I 2 ) strains. We challenged the immunized birds with a circulating wild virulent strain and noted some protection failure rates ( 35 ).…”