Objective—To characterize cytokine messenger RNA (mRNA) expression in intranasally vaccinated calves after bovine respiratory syncytial virus (BRSV) challenge.
Animals—Twelve 8- to 12-week-old calves.
Procedures—Calves received modified-live BRSV vaccine (vaccinated) or spent tissue culture medium (mock-vaccinated) intranasally, followed by challenge 30 days later with BRSV, or mock challenge with spent tissue culture medium (mock-challenge controls). Interleukin-4 (IL-4) and interferon-γ (IFN-γ) mRNA was measured in lungs, bronchoalveolar lavage (BAL) fluid cells, pharyngeal tonsils, and tracheobronchial lymph nodes, and tumor necrosis factor-α (TNF-α) mRNA was measured in lungs and BAL fluid cells by reverse transcriptase-competitive polymerase chain reaction assay.
Results—Resistance to clinical signs of disease was conferred in vaccinated calves. Expression of TNF-α mRNA in lungs and BAL fluid cells was higher in mock-vaccinated calves than control or vaccinated calves. In the lung, IL-4 mRNA expression was higher in vaccinated calves than control or mock-vaccinated calves. In pharyngeal tonsils, expression of mRNA for IL-4 and IFN-γ was higher in mock-vaccinated calves than control calves. In tracheobronchial lymph nodes, IFN-γ mRNA expression was higher in mock-vaccinated calves than vaccinated calves.
Conclusions and Clinical Relevance—Although vaccinated calves had decreased clinical signs of disease after BRSV challenge, compared with mock-vaccinated calves, this difference was not related to a T helper type 1 bias, as determined by increased expression of interferon-γ mRNA relative to interleukin-4 mRNA in lungs, BAL fluid cells, or tracheobronchial lymph nodes of vaccinated calves. Pulmonary inflammation was decreased in vaccinated calves as determined by decreased expression of TNF-α mRNA. (Am J Vet Res 2004;65:725–733)