EFFECTS OF HIGH MOLECULAR WEIGHT POLY-γ-GLUTAMIC ACID ON PIGS WITH PORCINE PREPRODUCTIVE AND RESPIRATORY SYNDROME VIRUS (PRRSV) INFECTION

Bacillus subtilis sups. chungkookjang produces a higher molecular mass poly-gamma-glutamic acid (gamma-PGA). Recently, previous studies have demonstrated immune stimulation and an antitumor effect of the high molecular mass gamma-PGA using various mouse models although these effects have not been shown in other species of animals. Therefore, the current study was conducted to determine the effect of gamma-PGA in pigs with and without PRRSV infection. PRRS-negative pigs were intramuscularly injected with 1, 3, or 5 ml of 20 mg/mll gamma-PGA, and one group of pigs served as a non-treatment (NT) group. All groups treated with gamma-PGA had signifi cantly higher weight gains, and pigs treated with 5 ml of.-PGA exhibited higher tumor necrosis factor (TNF)-alpha, interferon (IFN)-alpha and IFN-beta expression levels compared with the NT group. According to the preliminary results, an animal challenge study was conducted with a highly virulent PRRSV strain, MN184, along with gamma-PGA treatment at different time points. Pigs treated with.-PGA had lower levels of viral loads in the sera and in lungs and gained signifi cantly more weight (p< 0.05) compared with the NT group after being challenged with MN184. Moreover, gamma-PGA-treatment groups had higher levels of neutralizing antibodies and cytokines related to proinfl ammatory, humoral and cell-mediated responses than the control group after the PRRSV challenge. Therefore, it was concluded that gamma-PGA induces higher levels of immune responses and increases resistance to PRRSV infection in pigs.