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ADVERSE EFFECTS OF ADJUVANTS IN VACCINES ADVERSE EFFECTS ADJUVANTS VACCINES Adjuvants are chemical substances which are added to vaccines to boost immune response, but many of them are known to cause a range of serious side-effects. Part 1 of 2 [Editor's Note: This article refers to research studies involving animals. We wish to advise readers that we at NEXUS do not condone or support the validity, efficacy or morality of animal experimentation or vivisection.] ADJUVANTS, PRESERVATIVES AND TISSUE FIXATIVES IN VACCINES Viecines contain a number of substances which can be divided into the following groups: 1. Micro-organisms, either bacteria or viruses, thought to be causing certain infectious diseases and which the vaccine is supposed to prevent. These are whole-cell proteins or just the broken-cell protein envelopes, and are called antigens. 2. Chemical substances which are supposed to enhance the immune response to the vaccine, called adjuvants. 3. Chemical substances which act as preservatives and tissue fixatives, which are sup- posed to halt any further chemical reactions and putrefaction (decomposition or multipli- cation) of the live or attenuated (or killed) biological constituents of the vaccine. All these constituents of vaccines are toxic, and their toxicity may vary, as a rule, from one batch of vaccine to another. In this article, the first of a two-part series, we shall deal with adjuvants, their expected role and the reactions (side effects). ADJUVANTS The desired immune response to vaccines is the production of antibodies, and this is enhanced by adding certain substances to the vaccines. These are called adjuvants (from the Latin adjuvare, meaning "to help"). The chemical nature of adjuvants, their mode of action and their reactions (side effects) are highly variable. According to Gupta et al. (1993), some of the side effects can be ascribed to an unintentional stimulation of different mechanisms of the immune system, whereas others may reflect general adverse pharmacological reactions which are more or less expected. There are several types of adjuvants. Today the most common adjuvants for human use are aluminium hydroxide, aluminium phosphate and calcium phosphate. However, there are a number of other adjuvants based on oil emulsions, products from bacteria (their syn- thetic derivatives as well as liposomes) or gram-negative bacteria, endotoxins, cholesterol, fatty acids, aliphatic amines, paraffinic and vegetable oils. Recently, monophosphory] lipid A, ISCOMs with Quil-A, and Syntex adjuvant formulations (SAFs) containing the threony] derivative or muramy] dipeptide have been under consideration for use in human vaccines. Chemically, the adjuvants are a highly heterogenous group of compounds with only one thing in common: their ability to enhance the immune response—their adjuvanticity. They are highly variable in terms of how they affect the immune system and how serious their adverse effects are due to the resultant hyperactivation of the immune system. The mode of action of adjuvants was described by Chedid (1985) as: the formation of a depot of antigen at the site of inoculation, with slow release; the presentation of antigen to immunocompetent cells; and the production of various and different lymphokines (inter- leukins and tumour necrosis factor). The choice of any of these adjuvants reflects a compromise between a requirement for adjuvanticity and an acceptable low level of adverse reactions. by Viera Scheibner, PhD © 2000 178 Govetts Leap Road Blackheath, NSW 2785 Australia Telephone: +61 (0)2 4787 8203 Fax: +61 (0)2 4787 8988 178 Govetts Leap Road Blackheath, NSW 2785 Australia Telephone: +61 (0)2 4787 8203 Fax: +61 (0)2 4787 8988 NEXUS - 37 DECEMBER 2000 — JANUARY 2001