Objective:
Characterize the molecular basis of CSFV virulence in swine. Investigate the role of N- and O-linked glycosylation of CSFV envelope proteins that might be involved in virulence, generalization of infection, tissue tropism, virus transmission, immunogenicity, and induction of protection.

Approach:
Characterization of mutant viruses will be assessed in pigs by determining the ability to induce disease, as well as viral load in tonsils, transient viremia, nasal shedding, and induction of antibody response. Recovered viruses will be fully sequenced to assess the presence of potential changes in the genome. Generalization of infection will be assessed by immunohistochemistry and virus titration in post-mortem specimens. Viral proteins will be analyzed in pathogenesis studies in swine to determine the level of restriction of mutant viruses. Antigenicity and immunogenicity conferred by the introduced changes will be analyzed and measured in infected swine. The ability of modified viruses to protect against CSFV infection will be assessed in swine challenge experiments.