The new crown vaccine family “adds Ding” to the genetic recombinant vaccine to learn more
◎Wang Xinyu
A new member has recently been added to the lineup of my country's new crown vaccine approved for emergency use-a genetically recombined subunit vaccine.
This type of vaccine is different from the previously approved inactivated vaccines and adenovirus vector vaccines. One of the most concerned differences is that this vaccine requires 3 injections to complete the immunization program, with an interval of 6 months.
So, what is a genetic recombination subunit vaccine, and how was the earliest genetic recombination subunit vaccine developed?
Let us find out.
The antigens of inactivated vaccines and attenuated vaccines are composed of intact pathogens, while genetic recombination subunit vaccines only contain certain components derived from pathogenic bacteria or viruses.
These components are highly purified proteins or synthetic peptides, which are the main substances that cause the body's immune response.
In other words, genetically recombined subunit vaccines are not complete pathogens, so they are essentially not capable of infecting humans and causing diseases.
The world's first vaccine produced by genetic recombination technology is hepatitis B vaccine.
A unique feature of the hepatitis B virus is that, in addition to the entire virus particles, a large number of spherical and rod-shaped particles containing only the hepatitis B virus surface antigen (HBsAg) were found in the peripheral blood of virus carriers.
In some carriers, these particles account for more than 1% of their total serum protein.
This discovery forms the basis for the manufacture of genetically recombinant hepatitis B vaccine.
In the 1980s, scientists tried to use genetic recombination technology to make HBsAg, a subunit of the hepatitis B vaccine, expressed in other organisms. This technology freed the need for human plasma in vaccine production and provided almost unlimited vaccine production. potential.
In other words, scientists replaced HBsAg isolated from the plasma of infected persons with synthetic HBsAg.
At present, most of the approved genetic recombinant hepatitis B vaccines are composed of the S gene product (HBsAg protein) containing 226 amino acids.
The recombinant hepatitis B vaccine produced by yeast is made by expressing HBsAg protein in genetically engineered yeast cells (Saccharomyces cerevisiae or Hansenula) containing the S gene.
The expression plasmid only produces HBsAg protein in yeast cells and does not contain real virus.
The polypeptides expressing HBsAg in this genetic recombinant hepatitis B vaccine will automatically assemble into 22 nanometer spherical particles, similar to the HBsAg particles isolated from the serum of chronic hepatitis B virus infection.
This artificial HBsAg particle also contains antigenic determinants that play an important role in the immune response.
Of course, the recombinant hepatitis B vaccine is not perfect. Judging from a harsh perspective, it also has shortcomings.
One of the most prominent points is that the immunogenicity is not strong enough, which shows that a small part of the vaccinated people cannot produce protective antibodies after vaccination and need to be re-vaccinated.
In this regard, scientists have also developed a recombinant vaccine containing pre-S region genes. Facts have proved that this vaccine can produce better protection, but because the manufacturing cost is significantly higher than the existing vaccines, it is not widely used.
The World Health Organization and national health departments also believe that the existing genetically recombinant hepatitis B vaccine is good enough, and there is no plan to replace it with a new vaccine.
As a representative of genetically recombinant subunit vaccines, genetically recombinant hepatitis B vaccine has the advantages of high yield, high safety, easy storage and transportation, and has achieved great success.
The genetic recombination subunit COVID-19 vaccine developed using the same technical route should also have similar advantages.
Data from clinical studies also show that after 2 doses of genetically recombined subunit COVID-19 vaccine, 76% can produce neutralizing antibodies; after 3 doses, 97% can produce neutralizing antibodies, and the antibody level is high, which can achieve recovery. The patient's serum antibody level was twice as high.
It can be seen that the gene recombination subunit new crown vaccine has shown good potential in clinical research.
In the vaccination of a wider range of people, whether it can stand out among many new crown vaccine technical routes is also worth looking forward to.