Effect of Predated Vaccination and Chinese Herbal Adjuvant Rabbit Hemorrhagic Disease Vaccine on Immune Response in Young Rabbits

The experiments were conducted to determine effects of precocious vaccination compared to the classical schedule of vaccination and of Chinese herbal adjuvant (CHA) on immune response to vaccine against rabbit hemorrhagic disease (RHD) in young rabbits. In experiment 1, five New Zealand rabbits at 30, 35, 40 or 45 days of age were injected with 3 ml of non-adjuvant inactivated vaccine against RHD, respectively. The results showed that the titer of maternal HI antibody on day 0 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 titer was higher than 3 log2. In experiment 2, thirty 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 (half dose antigen of RHD vaccine) RHD vaccine, aluminium adjuvant-containing RHD vaccine, or phosphate-buffered saline (PBS), respectively. The results showed that the CHA promoted (P<0.05) the lymphocyte proliferation on day 7 and enhanced serum antibody titer on day 21. These findings from the two experiments suggested that vaccination could be carried out at 35 days and Chinese herbal adjuvant significantly enhanced the immune response to vaccine against RHD in comparison with aluminium adjuvant.