The humoral immunization potential of panax ginseng polysaccharide (GPS) against H9N2 avian influenza virus (H9N2 AIV) in chickens was investigated. The effects of GPS treatment before and during H9N2 AIV infection were determined in chicken embryo fibroblast (CEF) by MTT (3(4, 5-dimethylthiazol-2-yl)-2, 3-diphenyl tetrazolium bromide) assays and quantitative RT-PCR analysis of MHC and cytokine...