Pig Lung Immune Cytokine Response to the Swine Influenza Virus and the Actinobacillus Pleuropneumoniae Infection

Abstract

Introduction: The aim of this study was to evaluate and compare the local innate immune response to the swine influenza virus (SIV) and Actinobacillus pleuropneumoniae (App) infection in pigs.

Material and methods: The study was performed on 37 seven-week-old pigs, divided into four groups: App-infected (n=11), App+SIV-infected (n=11), SIV-infected (n=11), and control (n=4). Lung samples were collected, following euthanasia, on the 2^nd and 4^th dpi (three piglets per inoculated group) and on the 10^th dpi (remaining inoculated and control pigs). Lung concentrations of IL-1β, IL-6, IL-8, TNF-α, IL-10, IFN-α, and IFN-γ were analysed with the use of commercial porcine cytokine ELISA kits.

Results: Lung concentrations of IL-1β, IL-6, IL-8, TNF-α, IFN-α, and IFN-γ were induced in SIV-infected and App+SIV-infected pigs. In the lung tissue of App-infected pigs, only concentrations of IL-1β, IL-6, IL-8, and IFN-γ were elevated. Additionally, in App+SIV-infected pigs, significantly greater concentrations of IL-1β, IL-8, and IFN-α were found when compared with pigs infected with either SIV or App alone. In each tested group, the lung concentration of IL-10 remained unchanged during the entire study.

Conclusion: The results of the study indicate that the experimental infection of pigs with SIV or App alone and co-infection with both pathogens induced a local lung inflammatory response. However, the local cytokine response was considerably higher in co-infected pigs compared to single-infected pigs.

Keywords: Actinobacillus pleuropneumoniae; cytokines; local immunity; pigs; swine influenza virus.

Fig. 1

Gross lung lesions observed on the 4^th day post-inoculation (dpi) in pigs singly or doubly inoculated with SIV and/or App

Fig. 2

Concentration of cytokines in lung samples from pigs inoculated with SIV and/or App; a – significant difference between App-infected group and control group; b – significant difference between SIV-infected group and control group; c – significant difference between App+SIV-infected group and control group; d – significant difference between App+SIV-infected group and App-infected group; e – significant difference between App+SIV-infected group and SIV-infected group; f – significant difference between App-infected group and SIV-infected group