What are Synthetic Vaccines? How it works, Definition, Types

Synthetic Vaccines: Definition, Types, Advantages

Definition of Synthetic Vaccines

  • Synthetic vaccines are those vaccines that are made outside of a living cell. 

  • A synthetic vaccine is a vaccine consisting mainly of synthetic mRNA, DNA, peptides, carbohydrates, or antigens to treat infectious diseases. 

What are synthetic vaccines:

  • A synthetic vaccine is a vaccine consisting mainly of synthetic mRNA, DNA, peptides, carbohydrates, or antigens.
  • Synthetic vaccines are usually considered to be safer than vaccines from pathogenic cultures.
  • A goal of synthetic vaccine research has been to identify the most immunogenic microbial antigens or epitopes, to synthesize these in the laboratory.
  • mRNA vaccines are the first synthetic vaccines, meaning they are made outside of a living cell.
  • Some Examples of synthetic vaccines are mRNA vaccines, DNA Vaccines, Peptide Vaccines, etc.
  • Synthetic peptide vaccines are developed against infectious diseases such as malaria, hepatitis C, and foot-and-mouth disease.
  • This type of vaccine can induce multiple immune responses, including humoral immunity, cellular immunity, and mucosal immunity.

History of Synthetic Vaccines:

  • In the 18th century, Edward Jenner developed the smallpox vaccine, which proved to be a milestone in this field. 
  • Since then, these vaccines are being manufactured in many ways to generate immunity against infectious diseases in the human body. 
  • In the 20th century, a large number of vaccines were produced using inactivated viruses. 
  • Some of the latest vaccines are manufactured within cells or outside the cells.
  • The world's first synthetic vaccine was created in 1982 from diphtheria toxin by Louis Chedid (scientist) from the Pasteur Institute and Michael Sela from the Weizmann Institute. 
  • In 1986, Manuel Elkin Patarroyo created the SPf66, the first version of a synthetic vaccine for Malaria.

How do synthetic vaccines work?

These vaccines contain synthetic (that is, lab-made) strands of RNA or DNA that code for protein molecules on the virus's surface. Once the vaccine delivers the genetic material into cells, the cells follow the genetic instructions to churn out the viral protein.

Types of Synthetic Vaccines: 

1. Synthetic Peptide Vaccines

  • Synthetic peptide vaccines are developed from the antigenic determinants of pathogens.
  • In this type of vaccine epitope (a small part of the antigenic nucleotide sequence) plays a key role in the generation of the immune response. 
  • Using protein chemistry technology, the vaccine made by artificially synthesizing this part of the gene sequence with immune activity protective polypeptide or antigenic epitope is called synthetic peptide vaccine.
  • This kind of vaccine solves the problem that some pathogenic microorganisms cannot be cultured in vitro or has low growth titer, and can also induce strong cellular response and long immunization time. 
  • Synthetic peptide vaccines do not contain nucleic acid components, so they are safe, low-cost, and easy to produce. 
  • However, it has problems such as low immunogenicity, the need for suitable carriers or adjuvants, and the immature technology for screening and assembling antigenic epitopes.

2. Synthetic mRNA Vaccines

  • mRNA vaccine technology is the latest third-generation vaccine technology. 
  • After the mRNA vaccine is injected into the body, it is translated into the cytoplasm without entering the nucleus.
  • This technology can not only fully induce humoral and cellular immune responses, but also activate immune response adjuvants. 
  • It also has the advantages of fast development, high yield, low cost, and easier realization of multiplexed and multivalent designs. 
  • Given the easy degradation of mRNA vaccines, efficient mRNA delivery methods are generally used to solve the problem. 
  • Dendritic cells, protamine, macromolecular carriers, and lipid nanoparticles are commonly used as delivery carriers. 
  • In addition, immunogenicity, half-life, and expression stability can be improved by mRNA modification. 
  • Currently, mRNA vaccines in clinical trials include influenza virus vaccine, rabies virus vaccine, Ebola virus vaccine, Zika virus vaccine, and new coronavirus vaccine.

3. Subunit Vaccines

  • Subunit vaccines extract specific immunogenic components (peptides, proteins, or polysaccharides) from pathogens by chemical decomposition or controlled proteolysis, and screen out the fragments with immunological activity. 
  • The vaccine is called a subunit. Vaccines are also known as component vaccines. 
  • Compared with the inactivated vaccine, its composition is simple and the adverse reactions are reduced, but the immunogenicity is lower, and an adjuvant is needed to enhance the immunogenicity.
  • These types of vaccines are developed against diseases such as Hepatitis B, Pertussis, and Streptococcal pneumonia.
  • The currently widely used typhoid Vi polysaccharide vaccine, 23-valent pneumococcal polysaccharide vaccine, and meningococcal polysaccharide vaccine are prepared from long-chain or short-chain sugar molecules in the bacterial capsule. 
  • Subunit Vaccines are difficult to develop.
  • In addition, some polysaccharide conjugate vaccines can also be used as dual vaccines to prevent two diseases at the same time, such as the Haemophilus influenzae type b-diphtheria combined vaccine.

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