Analysis of immunological enhancement of immunosuppressed chickens by Chinese herbal extracts.

Ethnopharmacological Relevance: Radix astragali, Radix codonopis, Herba epimedii and Radix glycyrrizae are 4 plants commonly used in Chinese traditional medicine or veterinary medicine to improve immune functions against chronic diseases in humans and animals.

Aim Of The Study: We compared immunological enhancement by 4 herbal extracts in clinical healthy chickens or immunosuppressed chickens singly and in combination.

Materials And Methods: Water extracts of 4 herbs individually and in different combinations were supplemented in drinking water. Hemagglutination inhibition (HI) antibody titers against Newcastle disease virus (NDV) and H5 avian influenza virus (H5-AIV) after vaccination were measured as indicators to evaluate immunological stimulation across groups supplemented with different herbal extracts. The experiments were conducted in both clinically healthy chickens and chickens with immunosuppression induced by reticuloendotheliosis virus (REV) infection.

Results: In clinically healthy chickens HI antibody titers against NDV and H5-AIV after vaccination were not influenced by supplementation with the herbal extracts of Radix astragali, Radix codonopis, Herba epimedii and Radix glycyrrizae in drinking water. In chicks with REV-induced immunosuppression, however, supplementation of some herbal extracts significantly increased HI antibody titers to NDV and H5-AIV when compared to the immunosuppressed control group (P<0.01), but the titers were still lower than those in chicks not infected by REV. The 4 herbal mixtures produced the best enhancement among various combinations. The components of the herbal extract were water soluble and treatment by ether had no influence on immunological enhancement. The molecular weights of the active components of the herbal extracts were in the range of 10,000-100,000 Da.

Conclusion: Our results show that the herbal extract supplementation in drinking water can induce an immune stimulation response in immunosuppressed chickens. It suggests that chickens with REV infection-induced immunosuppression could be used as an experiment model for determination of immunological enhancement effects of some herbal components.