Two Kinds of Common Vaccine Adjuvants

Posted by Candy Swift on May 30th, 2019

What is an adjuvant? Adjuvant, also known as immunomodulator or immune enhancer, is an additive of a vaccine. When injected into the body prior to the antigen or mixed with the antigen, it can enhance the body's immune response to the antigen or change the type of immune response. Adjuvants is a non-specific immunopotentiator without antigenicity itself. The ideal adjuvant not only enhances the immune response, but also provides the body with optimal protective immunity.

At present, there is no uniform standard for the classification of adjuvants in the world. According to the chemical composition, it can be divided into aluminum salt adjuvant, protein adjuvant, nucleic acid adjuvant, lipid-containing adjuvant and mixed adjuvant.

1. Aluminum salt adjuvant

Aluminum salt has been used clinically for more than 80 years and is the first classic adjuvant approved by the FDA for human use. Many vaccine ingredients contain aluminum salts such as DTP vaccine and Haemophilus influenzae vaccine. Depending on the preparation process, vaccines with aluminum salts as adjuvants can be divided into two types: aluminum adsorption vaccines and aluminum precipitation vaccines. The aluminum adsorption vaccine is to add an antigen to an aluminum hydroxide or aluminum phosphate solution; and the aluminum precipitation vaccine is to add an aluminum suspension to the antigen solution. Aluminum hydroxide or aluminum phosphate is an aluminum adjuvant that is often used. The study found that aluminum adjuvant vaccine can reduce the amount of antigen used and enhance the strength and durability of the body's immune response.

The mechanism of action of aluminum salts is still not clear. It is generally believed that the antigen-adsorbed aluminum salt particles form a gel state and are injected into animals to form an antigen reservoir. These insoluble particles can adsorb antigenic substances and increase the surface area of ​​the antigen. In addition, the adjuvant can form a macrophage-rich granuloma at the injection site, delaying the absorption of the antigen, thereby prolonging the stimulation time of the antigen, and retaining the antigen for several days under normal conditions for a few weeks. Studies have shown that aluminum hydroxide as an adjuvant can also activate Th2 cells to secrete IL-4, induce the expression of CD83, CD86 and MHC-II molecules, and then produce a Th2 type humoral immune response. Aluminum salts have many advantages as vaccine adjuvants, but there are also deficiencies. Although it can effectively induce a humoral immune response, it does not act on cellular immunity and cannot induce a cellular immune response.

2. Protein adjuvants

Most of protein adjuvants belong to small molecule polypeptides or glycoproteins in vaccine adjuvant selection. A class of biologically active substances synthesized and secreted by immune cells and certain non-immune cells, generally cytokines, play an important role in the differentiation of Th cells. It can also enhance the function of NK cells and T lymphocytes, and has a wide-ranging effect on the immune response of the body. The use of a protein adjuvant in combination with an antigen enhances the immunogenic efficacy of the vaccine, and it can also be assembled into a plasmid and mixed with the antigen for injection. IL-12 is produced by monocytes and B cells and has a variety of biological activities. It can significantly reduce the number of bacterial invasions and increase the expression levels of IgG2a and IgA in the mucosa and immune system. It is a cytokine with broad application prospects. Adjuvant. It induces a Th1-type immune response, and the treatment of tumors and AIDS is in clinical trials.