NEW YORK (Reuters) - The United States could authorize emergency use of some currently unapproved immune system boosters called adjuvants to make a swine flu vaccine more effective, an official at the U.S. Centers for Disease Control and Prevention said on Thursday.

A big challenge facing manufacturers of a vaccine for the new swine flu story"H1N1 flu will be making sufficient quantities of vaccine from a limited supply of active ingredient, or antigen.

"There are a couple of adjuvants that are being looked at now," he said. "There's nothing that's been approved for use in the United States, but there are several that could possibly get emergency use authorization if it appeared it was called for."

Immunologists have a special name for substances used to boost feeble vaccines. They are called adjuvants. Adjuvants are arguably the most extensively researched pharmaceutical product in the last quarter century that you never heard of. I have used the word adjuvant three times in this paragraph so far and that is probably three times more than you have ever seen it in print before. This is partly because the most effective adjuvants, those formulated with oils, are too dangerous for human use. That is squalene's other proven ability, causing incurable disease, which is why it is such a touchy subject with the Department of Defense.

ADJUVANTS, PRESERVATIVES AND TISSUE FIXATIVES IN VACCINES

Vaccines 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 supposed to halt any further chemical reactions and putrefaction (decomposition or multiplication) 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 expects 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 effect) 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 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 synthetic derivatives as well as liposomes) or gram-negative bacteria, endotoxins, cholesterol, fatty acids, aliphatic amines, paraffinic and vegetable oils. Recently, monophosphoryl lipid A, ISCOMs with Quil-A, and Syntex adjuvant formulations (SAFs) containing the threonyl derivative or muramyl 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.

Iowa State University researchers are reported to be planning experimental insertion of 'swine flu vaccines' into the genetic makeup of corn. The idea is to allow pigs and humans to get a flu vaccination "simply by eating corn or corn products." So many questions come to mind about potential unintended consequences. It would be interesting to see whatever ethics or social responsibility evaluations of the proposed work may have been sent to the school's Plant Sciences Institute.