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Foot-and-mouth disease virus virulence in cattle is co-determined by viral replication dynamics and route of infection

Jonathan Arzt, Juan M. Pacheco, George R. Smoliga, Meghan T. Tucker, Elizabeth Bishop, Steven J. Pauszek, Ethan J. Hartwig, Teresa de los Santos, Luis L. Rodriguez
Virology 2014 v.452-453 pp. 12-22
Foot-and-mouth disease virus, RNA, aerosols, antiviral properties, avirulent strains, blood, cattle diseases, disease severity, drug delivery systems, epithelial cells, foot-and-mouth disease, immune response, interferons, mutants, pathogenesis, phenotype, steers, virulence, virus replication, viruses
Early events in the pathogenesis of foot-and-mouth disease virus (FMDV) infection in cattle were investigated through aerosol and intraepithelial lingual (IEL) inoculations of a cDNA-derived FMDV-A₂₄ wild type virus (FMDV-WT) or a mutant derived from the same clone (FMDV-Mut). After aerosolization of FMDV-WT, primary infection sites had significantly greater quantities of FMDV, viral RNA, and type I/III interferon (IFN) activity compared to corresponding tissues from cattle infected with FMDV-Mut. Additionally, FMDV-WT-infected cattle had marked induction of systemic IFN activity in serum. In contrast, FMDV-Mut aerosol-infected cattle did not manifest systemic IFN response nor had viremia. Interestingly, IEL inoculation of FMDV-Mut in cattle restored the virulent phenotype and systemic IFN response. These data indicate that the attenuated phenotype in cattle is associated with decreased replicative efficiency, reflected by decreased innate response. However, attenuation is abrogated by bypassing the common primary infection sites, inducing accelerated viral replication at the inoculation site.