Vaccine with herbal adjuvant—A better cocktail to combat the infection

Abstract

Cross-talk between microbe and the host makes important contribution to the subsequent course of infection. Edward Jenner and Louis Pasteur—Fathers of vaccinology have wisely thought of combating an infectious bug with the same bug in a non-infectious form. Then on, vaccines have taken a great toll as a prophylactic agent to improve the quality of human life. Vaccines are successful in controlling a substantial portion of the morbidity and mortality in the developing world. Though vaccines against few diseases like small pox, polio and cholera are highly successful, the stories of failed vaccines are far more. An ideal vaccine candidate should be able to elicit the correct response, either Th1 or Th2 to combat the infection along with a strong immune memory. Use of adjuvant in the vaccine preparation is a long standing practice. Despite major advances in our understanding of vaccine adjuvants, both old and new vaccines seem likely to depend on aluminium salts. However, these adjuvants can lead to serious adverse effects [1]. Herbal immuno-modulators are paving its way as a safe alternative [2-7]. These herbal modulators can be administered along with the vaccine to elicit a faster and stronger immune response. Various herbal preparations have been shown to exert strong immuno-modulatory properties like increase in the cytokine expression [6], enhanced activation of CD4 and CD8 T cells [4-6], enhanced NK cell activity [4], etc. The failure of various vaccines can be attributed to its inability to trigger a robust immune response necessary for protection due to subsequent exposure to an infectious agent. Use of herbal immuno-modulators perhaps might be helpful in overcoming the initial lag. For, e.g., Angelica sinensus polysaccharide (ASP) increased the production of IL-2 and IFNγ, while that of IL-4 was decreased [6]. Hence, in bacterial and viral infections, which need IFNγ for its clearance, can use ASP as an adjuvant along with the vaccine. Similarly, infections which need IL-4 for its clearance should be combined with herbal modulators favoring Th2 responses, like ginseng [3]. Herbs are usually considered to be safe. However, there is no database available which can summarize the immunological profile of the various herbs or polyherbs preparation. Hence, a note of caution is a must before choosing herbal immuno-modulators as an adjuvant.