# Construction and Immunogenicity Evaluation of a Recombinant Infectious Bronchitis Virus H120-Based Vaccine in Broiler Chickens

## TL;DR

A new recombinant vaccine for Infectious Bronchitis Virus was developed and shown to be effective in chickens.

## Contribution

A genetically defined recombinant IBV vaccine using Golden Gate Assembly was developed and tested for immunogenicity.

## Key findings

- The recombinant H120 virus (rH120) replicated efficiently in broiler chickens and induced a strong antibody response.
- rH120 showed similar growth characteristics to the original H120 strain in SPF chicken eggs.
- The virus was genetically stable and demonstrated strong immunogenicity in broiler chickens.

## Abstract

Infectious Bronchitis Virus (IBV) remains a major threat to poultry production due to its genetic diversity and the limited cross-protection of current vaccines. In this study, we developed a recombinant H120 virus (rH120) using a Golden Gate Assembly-based reverse genetics system that assembled 12 synthetic genome fragments. The virus was successfully rescued in chicken fibroblast cells, propagated in embryonated SPF eggs, and showed growth characteristics similar to the original H120 strain. In broiler chickens, rH120 replicated efficiently and induced a strong antibody response, confirming its immunogenicity. These results demonstrate that Golden Gate Assembly provides a robust platform for generating genetically defined IBV vaccine candidates.

Infectious Bronchitis Virus is one of several major viral infections in poultry, affecting the respiratory, reproductive, and renal systems and causing significant economic losses worldwide. Current vaccines, including the H120 strain, provide limited cross-protection against emerging variants, underscoring the need for improved vaccine strategies. In this study, the complete genome of IBV H120 was divided into 12 fragments, synthesized, and assembled using the Golden Gate Assembly (GGA) method. The recombinant virus (rH120) was successfully rescued in chicken fibroblast cells and propagated in embryonated specific-pathogen-free (SPF) chicken eggs. Growth kinetics in embryonated SPF chicken eggs revealed similar replication patterns between rH120 and the original H120 strain. In broiler chickens, rH120 replicated efficiently, as confirmed by viral RNA detection in throat and cloacal swabs, and induced a stronger antibody response by 14 days post-infection. The rH120 virus proved to be genetically stable, infectious, and immunogenic, indicating that GGA-based reverse genetics is an effective system for IBV vaccine development.