Subunit vaccine is made from special immunologically active protein fragments extracted by chemical decomposition or proteolysis from bacteria and viruses. A subunit vaccine is made up of components that present the major protective immunogens of pathogenic bacteria, also known as component vaccines.

What is a subunit vaccine? The vaccine, which does not contain nucleic acid and can induce the body to produce antibodies, is made up by a certain surface structural component (antigen) of microorganisms, called subunit vaccine.

Among the multiple specific antigenic determinants carried by macromolecular antigens, only a small number of antigenic sites contribute to the protective immune response. The special protein structure of bacteria and viruses is extracted by chemical decomposition or controlled proteolysis, and the vaccine prepared by immunologically active fragments is selected as a subunit vaccine.

Subunit vaccine has only a few major surface proteins, avoiding the production of many unrelated antigen-induced antibodies which reducing vaccine side effects and vaccine-related diseases.

The shortcoming of the subunit vaccine is that it is less immunogenic and needs to be combined with an adjuvant to produce a good immune effect. In the 1970s and 1980s, virion subunits and surface antigen (HA and NA) vaccines were developed on the basis of split vaccines. The influenza virus membrane proteins HA and NA were cleaved by appropriate lysing reagents and cleavage conditions, and obtained by appropriate purification methods. Subunit influenza vaccines have very pure antigenic components. In clinical trials in the UK, the subunit influenza vaccines has been demonstrated that the immune effect is the same as that of the split vaccine and can be used in children. It was first approved for use in the UK in 1980 and then extended to other countries.



Subunit vaccine application—recombinant subunit vaccine

Recombinant subunit vaccine, also known as genetic engineering subunit vaccine and biosynthetic subunit vaccine, is made from protective antigen gene products, proteins or peptides, expressed in prokaryotic or eukaryotic cells. Traditional vaccines are often made by serial passage or chemical or physical inactivation of certain components. Although they are effective, there is a risk of reversal of virulence. Subunit vaccines prepared by molecular biology techniques are superior in safety to traditional vaccines. Non-recombinant subunit vaccines are vaccines consisting of individual proteins or oligosaccharides, such as bacterial lipopolysaccharides purified from pathogenic microorganisms. Subunit vaccines often require adjuvants or various conjugates to enhance their immunogenicity, and the production of these vaccines usually requires the large-scale cultivation of pathogenic microorganisms, which is costly and has certain risks.



Advantages: 1. High safety; 2. High purity, good stability; 3. High yield; 4. For vaccine research that is difficult to culture or potentially carcinogenic, or pathogenic.

Disadvantages: Compared with traditional subunit vaccines, the immune effect is poor.



Ways to enhance its immunogenicity:

1. Adjust the gene combination to express it into a granular structure;
2. Coagulatein vitro, encapsulated into liposomes or capsule microspheres;
3.An immunopotentiating compound is added as an adjuvant;
The expression systems for subunit vaccine production mainly include Escherichia coli, Bacillus subtilis, yeast, insect cells, mammalian cells, transgenic plants, and transgenic animals.

The more successful genetic engineering subunit vaccine is the hepatitis B surface antigen vaccine.