Recombinant Antigen for Newcastle Disease Virus Vaccine Focusing on Currently Circulating Virus Variants

Newcastle disease virus (NDV) causes a highly contagious avian infection and is characterised by its high genetic diversity and mutation rate. Currently applied vaccines are based on NDV genotypes I and II, which are considerably distinct from the circulating pathogenic genotypes, of which genotype VII is predominant, and therefore, they may not provide complete protection for birds or stop virus transmission. This work is a proof-of-concept study aiming to develop a genotype VII-focused recombinant antigen for a vaccine targeting relevant NDV strains. The research primarily focuses on novel antigen design based on the bioinformatics analysis of recent circulating isolates. Haemagglutinin-neuraminidase (HN) is one of the two main NDV antigens. Two HN fragments ("1"-341-368 aa and "2"-239-257 aa) were selected due to the presence of linear neutralising epitopes. An approach focusing on using a number of selected-fragment variants simultaneously was applied for the first time. The resulting antigen Castle1 encompasses the sequence diversity of most circulating isolates. Preliminary immunological evaluation showed that antibodies from Castle1-immunised animals possessed haemagglutination inhibition activity and interacted with NDV of genotypes I and VII. That makes Castle1 a promising antigen for the further development of a vaccine for preventing ongoing and incoming NDV outbreaks.