Submitted to: Pig Veterinary Society International Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: April 21, 2008
Publication Date: June 25, 2008
Citation: Brockmeier, S., Vincent, A.L., Loving, C.L., Nicholson, T.L., Sacco, R.E. 2008. Early Induction of Cytokines in Pigs Coinfected with Swine Influenza Virus and Bordetella bronchiseptica. In: Proceedings of the 20th International Pig Veterinary Society Congress, June 22-26, 2008, Durban, South Africa. 1:10. Technical Abstract: Respiratory disease is one of the most important health issues for the swine industry, and coinfection with two or more pathogens is a common occurrence. Bordetella bronchiseptica and swine influenza virus (SIV) are important and common respiratory pathogens of pigs. The effect of coinfection of SIV and B. bronchiseptica was examined in 4-week-old pigs that were infected with SIV, B. bronchiseptica, or SIV and B. bronchiseptica. Four pigs from each group were euthanized at 1, 5 and 10 days post infection. Although there was no difference in the frequency or amount of SIV isolated among the groups, there was a significantly greater amount of B. bronchiseptica isolated from coinfected pigs at day 1 and day 10 after challenge. Lung lesions in the coinfected pigs were more severe on day 1 and 10 after challenge, as well. To test the hypothesis that production of early cytokines might play a role in inducing the early lesions, mRNA expression of cytokine genes from tracheal epithelium and lung were evaluated by using RT-PCR. On day 1 post-infection, increased levels of IFNa transcript were found in the tracheal epithelium of only coinfected pigs, and the amount of IFNa detected in the lung lavage by ELISA was significantly higher in the coinfected pigs as well. Increased transcript levels of Mx-1 and PKR, two anti-viral proteins upregulated in response to IFNa, were also elevated in the tracheal epithelium and lung of only coinfected pigs at the same time point. In addition, transcripts for the proinflammatory cytokines IL-6, IL-8 IL-1, and TNFa were increased to a greater extent in the tracheal epithelium and/or the lung of coinfected pigs as compared to pigs infected with either pathogen alone, on day 1 post infection. This data suggests that there is a synergistic effect during coinfection with SIV and B. bronchiseptica leading to the early induction of these cytokines, contributing to the early inflammatory lesions seen in coinfected pigs.