Evaluation system for an experimental study of low-pathogenic avian influenza virus (H9N2) infection in specific pathogen free chickens using lactic acid bacteria, Lactobacillus plantarum KFCC11389P.

In low-pathogenic avian influenza (LPAI) virus, the effects of prophylactic oral administration of Lactobacillus plantarum KFCC11389P on immunity, viral loads and levels of nitric oxide and interferon-gamma in splenocytes from specific pathogen free (SPF) chickens were investigated. For in vitro screening of the antiviral effect, haemagglutination activities of four different lactic acid bacterial strains by direct contact with virus were measured. L. plantarum KFCC11389P only neutralized the virus on the SPF eggs. For in vivo studies, four groups of chickens were fed with various L. plantarum KFCC11389P bacterial components and were then challenged with LPAI virus at 28 days. Additionally, two control groups were used as negative (virus-unchallenged) control and positive (virus-challenged) control. We show that some parameters such as nitric oxide production in serum and splenic adherent cells and interferon-gamma levels in splenic cells from SPF chickens could be used for the evaluation of LPAI virus infection. This is the first report demonstrating the interferon-gamma production in cultured splenic mononuclear cells and nitric oxide production in serum as well as virus shedding in trachea and cloacae in LPAI virus-infected SPF chickens fed specific lactic acid bacterial components.