AS04

AS04 is an adjuvant system used in vaccines to enhance the body's immune response to an antigen. It is a proprietary formulation developed by GlaxoSmithKline (GSK), a British multinational pharmaceutical company. AS04 combines monophosphoryl lipid A (MPL), a toll-like receptor 4 (TLR4) agonist, and aluminum hydroxide, an aluminum salt.

Composition

AS04 consists of two main components: MPL and aluminum hydroxide. MPL is a derivative of the lipopolysaccharide (LPS) found in the cell wall of Salmonella minnesota. It is a potent activator of the innate immune system, triggering a response via TLR4. Aluminum hydroxide is used as an adjuvant in many vaccines due to its ability to stimulate a stronger immune response.

Mechanism of Action

The components of AS04 work synergistically to enhance the immune response to an antigen. MPL activates the innate immune system, leading to the production of pro-inflammatory cytokines and the activation of antigen-presenting cells (APCs). These APCs then present the antigen to T cells, initiating the adaptive immune response. Aluminum hydroxide enhances this response by providing a depot effect, prolonging the exposure of the antigen to the immune system.

Use in Vaccines

AS04 is used in several GSK vaccines, including Cervarix, a vaccine against human papillomavirus (HPV), and Fendrix, a vaccine against hepatitis B. The use of AS04 in these vaccines has been shown to enhance the immune response, leading to higher antibody levels and longer-lasting immunity compared to vaccines using aluminum salts alone.

Safety and Efficacy

AS04 has been extensively studied for its safety and efficacy. Clinical trials have shown that vaccines containing AS04 are well-tolerated and highly effective. However, as with all vaccines, side effects can occur. The most common side effects are mild and include pain at the injection site, fatigue, and headache.

See Also

• Adjuvant
• Vaccine
• Immune response
• GlaxoSmithKline