Application of lentinan in suppression of Marek's disease virus infection

Abstract

Marek's disease virus (MDV) is an extremely widespread avian immunosuppressive virus. In recent years, many reports have shown that there are still cases of MDV infection and immunosuppression after immunization with the vaccine. Consequently, there is a need to develop alternative complementary approaches for strengthening the efficacy of MDV prevention and control measures. Lentinan (LNT) is a macromolecular compound with immune-enhancing activity extracted from shiitake mushrooms. To explore the value and effectiveness of administering LNT through drinking water in the prevention and control of MDV, this study first observed the effects of high and low doses of LNT on weight gain, organ development, viral replication, and antibody titer of an avian influenza virus subtype H9 (AIV-H9) inactivated vaccine in specific pathogen-free (SPF) chicks infected with the wild strain of MDV. The results showed that both high and low doses of LNT significantly alleviated the weight gain retardation and liver and spleen enlargement caused by MDV infection, and significantly inhibited the replication of MDV in SPF chicks (P < 0.05), compared with the MDV-positive control group, both high and low doses of LNT significantly increased the antibody titer of AIV-H9 after immunization with inactivated AIV-H9 vaccine (P < 0.0001). On this basis, we also observed the effects of a chicken Marek's disease meq gene deletion live vaccine (SC9-1 strain), administered alone or in combination with LNT, on MDV infections of varying virulence in Hy-Line Brown chicks. The results showed that combined administration of LNT and the SC9-1 vaccine resulted in a significant alleviation of weight gain retardation and liver and spleen enlargement due to MDV infection (P < 0.05), as well as a significant inhibition of MDV replication and release in Hy-Line Brown chicks compared to the vaccine alone (P < 0.0001). These findings suggest that LNT not only alleviates the adverse effects of MDV infection in chickens but also enhances the efficacy of MDV vaccination, offering a potential auxiliary measure for controlling MDV infection.