The present invention relates to Porcine Reproductive and Respiratory Syndrome Virus (PRRSV) mutant strains having increased stability; compositions containing the strains or antigens derived therefrom; vaccines containing the strains, including killed, attenuated or subunit vaccines; nucleic acids encoding PRRSV polypeptides, polypeptides encoded by the nucleic acids, including antigenic fragments thereof; antibodies which specifically bind to said polypeptides, and methods making and using thereof.

The invention provides isolated polynucleotide molecules that comprise a DNA sequence encoding an infectious RNA sequence encoding a genetically-modified North American PRRS virus, methods to make it and related polypeptides, polynucleotides, and various components. Vaccines comprising the genetically modified virus and polynucleotides and a diagnostic kit to distinguish between naturally infected and vaccinated animals are also provided.

Provided are a chimeric virus expressing a porcine reproductive and respiratory syndrome virus (PRRSV)-derived peptide and a use thereof as a vaccine. The chimeric virus has an excellent immune stimulating effect and is useful as a vaccine that can effectively protect against PRRSV by suppressing viral amplification in target cells.

Workflows for the efficient identification of viral epitopes and/or host paratopes are provided. The workflows leverage artificial intelligence to quickly and reliably identify candidate epitopes for immunogen development thereby reducing the lead time of vaccine development. Immunogenic compositions for use in the treatment and/or prevention of porcine reproductive and respiratory syndrome virus (PRRSV) and Infectious Bronchitis Virus (IBV) are also provided, as are antibodies or antigen binding fragments.