Cytokine and Toll-like Receptor mRNAs in the Nasal-associated Lymphoid Tissues of Cattle During Foot-and-mouth Disease Virus Infection

The pharyngeal region is known to play an important role in foot-and-mouth disease virus (FMDV) infection in relation to acute disease and viral persistence. In this study, the local mucosal immune response in nasal-associated lymphoid tissue (NALT) of cattle infected with FMDV (strain O UKG 34/2001) was examined. Quantitative “real-time” RT-PCR assays were used to measure mRNA expression of cytokines (IFN-α, β and γ, IL-2, IL-1α and TNF-α) and Toll-like receptors (TLR)-3 and -4. NALTs from dorsal soft palate were collected from cattle at 7 days post-infection (dpi) and from carriers and non-carriers at 64 dpi. Expression of IFN-α mRNA was significantly greater in NALT during acute disease than in uninfected animals. Increased expression of IFN-γ and IL-1α mRNA was also observed but was much lower than IFN-α expression. There was a slight increase in mRNA expression of TNF-α and IL-2. During persistence, TNF-α mRNA expression in carrier cattle was much higher than in non-carrier cattle. Expression of TLR-4 in NALT during the acute stage of infection was greater than in uninfected animals. Carrier and non-carrier cattle did not differ in respect of expression of TLR-3 and -4 mRNA in NALT.