Location: Endemic Poultry Viral Diseases Research
Project Number: 6040-32000-084-010-T
Project Type: Trust Fund Cooperative Agreement
Start Date: Oct 14, 2025
End Date: Jun 30, 2027
Objective:
1. Construct rLS/IL4R and TS09-based vectored vaccines expressing the prefusion F protein and subtype-specific G protein (Ga or Gb) of aMPV-A or B.
2. Assess the safety and suitability of these recombinants for in-ovo and mucosal vaccination.
3. Evaluate the protective efficacy of the vaccine candidates against aMPV-A and B challenges in chickens and turkeys. Following in-ovo vaccination in chickens or mucosal vaccination in young turkeys, we will challenge chickens and turkeys with virulent US strains of aMPV-A and B.
Approach:
The rLS/IL4R and TS09 vectors will be engineered to co-express the prefusion form of the aMPV F protein and the subtype-specific G protein. Recently, the prefusion form of the human metapneumovirus (hMPV) fusion protein, a close relative of aMPV, has been determined. Fusion polypeptides engineered to be locked in this prefusion conformation are highly desirable for vaccine development as it represents the specific shape that neutralizing antibodies recognize. Based on crystallography data, we will use an AI-guided approach to identify key amino acid substitutions that stabilize the aMPV F proteins into their prefusion conformations. We will synthesize DNA fragments encoding the prefusion F and subtype-specific G protein genes with a P2A self-cleaving linker between F and G (F-P2A-G) to ensure the expression of both proteins from a single mRNA. These F-P2A-G fragments will be inserted into the rLS/IL4R and TS09 vectors, and recombinant viruses will be reconstituted, each of them co-expressing the prefusion F and subtype-specific G proteins. Subsequently, we will assess the safety of these recombinant viruses along with the previously made recombinant viruses containing the wildtype F and G genes of aMPV-B by performing the ICPI and MDT assays. The suitability of these vaccine candidates for in-ovo vaccination will be assessed by calculating hatch and survival rates and measuring humoral immune responses. Finally, we will evaluate the protective efficacy of selected vaccine candidates through in-ovo vaccination in commercial chicken eggs and mucosal vaccination via an intranasal/eye drop route in young turkeys, chickens, or breeding birds before the onset of lay against the challenges of aMPV-A and -B. The vaccine effectiveness will be determined by scoring clinical signs, measuring challenge virus shedding, and possibly comparing growth rates with the unchallenged control group after the challenge.