Enhancement of the Immune Response to Rabbit Hemorrhagic Disease Vaccine in Young Rabbits by Advanced Vaccination and Chinese Herbal Adjuvants

Experiments were conducted to determine the effects of advanced vaccination and Chinese herbal adjuvants (CHA), containing astragalus polysaccharides (APS) and ginsenosides (GS) on the immune response to rabbit hemorrhagic disease (RHD) vaccine in young rabbits. In experiment 1, 5 New Zealand rabbits of each group at 30, 35, 40, or 45 days of age were injected with 2 mL of inactivated RHD vaccine, respectively. The dynamic changes of antibody titers were tested by the hemagglutination inhibition (HI) method. In experiment 2, 30 New Zealand rabbits at 35 days of age were randomly assigned to 5 treatment groups, representing inoculation with 3 mL of non-adjuvant RHD vaccine, CHA-RHD vaccine, CHA-HA vaccine (half dose antigen), aluminium adjuvant-RHD vaccine, and PBS, respectively. The dynamic changes of peripheral lymphocyte proliferation and serum antibody titers were tested by the MTT method and the HI method. The results showed that the titer of maternal HI antibody in the 35-day-old rabbits was lower than the protective level of 3 log2, while on days 7 to 49 after the vaccination, the antibody titers were higher than 3 log2. The CHA promoted the lymphocyte proliferation and enhanced the serum antibody titer (P < 0.05). These findings from the two experiments suggested that advanced vaccination and Chinese herbal adjuvants significantly enhanced the immune response to vaccine against RHD, and effectively protected the young rabbits against RHD challenge.