Ginsenoside Rg1 as an adjuvant enhances immunity in chickens immunized with the H9N2 avian influenza inactivated vaccine

To investigate the potential use of Ginsenoside Rg1 as an adjuvant for the H9N2 avian influenza vaccine, the study examined Rg1’s immunomodulatory effects on an inactivated H9N2 vaccine. A total of 150 one-day-old non-immunized Arbor Acres (AA) chickens were randomly assigned to three groups ( n = 50 each): one receiving the H9N2 inactivated vaccine, another receiving Rg1 alongside the vaccine, and a control group treated with PBS. Each group underwent three immunization sessions spaced 2 weeks apart. Serum samples were taken to measure IgG antibody levels and hemagglutination inhibition (HI) titers. Lymphocyte proliferation was assessed using cell counting kits-8 and flow cytometry. The levels of serum cytokines, including Interferon-γ (IFN-γ), tumor necrosis factor-alpha (TNF-α), interleukin (IL)-4, and IL-6, were quantified via ELISA. Fourteen days post-final immunization, the chickens were challenged with the H9N2 strain, and viral titers in the lungs and kidneys were measured. Findings indicated that the group receiving Rg1 with the vaccine exhibited a notable increase in specific IgG and HI titers. Furthermore, this group showed enhanced T cell proliferation and elevated cytokine production, thereby bolstering cellular immunity. Importantly, the immune protection results revealed that the combination of Rg1 and the vaccine significantly improved the chickens’ protection against viral strains, leading to a marked reduction in viral shedding. These findings imply that Rg1 may enhance the immune response and protective efficacy of the H9N2 inactivated vaccine, positioning it as a promising new adjuvant for H9N2 vaccination.