mRNA vaccine Quality Control

mRNA vaccine Quality Control

Since the first case of COVID-19 has been confirmed in late 2019, as of mid-June 2020, the cumulative number of confirmed cases worldwide has reached 7.91 million, and the number of deaths has exceeded 430,000, and the number of confirmed cases worldwide continues to increase by 60,000 to 80,000 per day. Under such an urgent situation, the development of vaccines has become an important topic.

Technology platforms

Under the COVID-19 epidemic, relevant institutions around the world are currently developing vaccines urgently. On May 20, according to the statistics of the World Health Organization, there are more than 120 candidate vaccines currently under development worldwide. In general, the technologies being developed for the COVID-19 vaccine are focusing on 5 platforms. Including attenuated viruses, inactivated viruses, recombinant proteins, non-replicating viral vectors, and nucleic acid vaccines (i.e. DNA vaccines or RNA vaccines). The types of vaccines developed worldwide vary, and each has advantages and disadvantages. The first two vaccines to enter clinical trials were mRNA-1273 developed by Moderna, Inc. in collaboration with the National Institute of Allergy and Infectious Diseases, and by CanSino Biological and the Institute of Bioengineering, Academy of Military Medical Sciences, Chinese Academy of Military Sciences Ad5-nCoV vaccine based on adenovirus vector. The mRNA-1273 jointly developed by Moderna and the National Institute of Allergy and Infectious Diseases belongs to the mRNA vaccine in the nucleic acid vaccine. The development time of the mRNA vaccine is relatively short, so it can enter clinical trials very quickly. attenuated viruses, inactivated viruses, recombinant proteins, non-replicating viral vectors, and nucleic acid vaccines (i.e. DNA vaccines or RNA vaccines).

Table 1：Comparison of different types of vaccine

Nucleic acid vaccines are divided into mRNA vaccines and DNA vaccines. DNA vaccines inject the DNA encoding S protein directly into the nucleus of human cells, and use human cells to produce S protein to activate the immune response. This technology has a fast immune response and simple technology, but it is not immunogenic. Strong, the introduction of foreign DNA is a safety controversy; mRNA vaccine is one of the hottest technologies at present. From the perspective of the immune response triggered and easy to mass production, mRNA vaccine has advantages that other vaccines cannot compare with.

Advantages of mRNA Vaccine

Compared with traditional recombinant protein vaccines, inactivated vaccines and attenuated vaccines, mRNA vaccines have the advantages of simple preparation steps, low cost, strong immune response, long immunization period and high safety. In addition, mRNA vaccines are more resistant to high temperatures and more stable than traditional recombinant vaccines. Traditional vaccines require cold-chain transportation and storage in the refrigerator. If transported or improperly stored, it is easy to cause vaccine failure. mRNA vaccines can be effectively stored at 40 ℃ for one year , Can be effectively stored at 70 ℃ for three months. Moreover, mRNA drugs do not have the risk of integrating the host genome, and will automatically degrade in the body. The production cycle takes only about one month. This is of great significance for the control of infectious diseases. 

Moderna, Inc. completed the study of the mRNA vaccine sequence on the third day of the publication of the COVID-19 gene sequence. The mRNA-1273 vaccine it developed was one of the first covid-19 vaccines to enter clinical trials. In addition, RNA vaccines also play an important role in the treatment of non-infectious diseases such as tumors. Currently, three well-known RNA vaccine companies in the world, Moderna, BioNTech, and CureVac, have all established RNA vaccine product lines in cancer treatment, and some of them have also entered clinical trials.

How mRNA Vaccine work
mRNA is a type of single-stranded ribonucleic acid transcribed from DNA, which carries genetic information and guides protein synthesis. The principle of mRNA vaccine is to inject mRNA fragments with antigen genes into host cells, and the injected cells will synthesize and express antigen Protein, and the body's immune system will recognize these specific antigens and then generate an immune response. 
In theory, mRNA has the potential to synthesize any kind of protein. After solving the stability and delivery problems of mRNA, in addition to being used as a vaccine, mRNA can also be used as a protein supplement or alternative therapy to treat various other diseases. Therefore, traditional vaccines are unable to respond to Many new viruses, cancers, metabolic diseases, etc., mRNA vaccines have great potential for application.

Clinical trials started in 2020

source link: https://en.wikipedia.org/wiki/COVID-19_vaccine

Disadvantages of mRNA Vaccine and Quality Control

Of course, the mRNA vaccine also has its disadvantages. First, the mRNA is unstable, and it is easily broken down by cells after injection; second, it is easy to produce double-stranded RNA during the synthesis of mRNA. This impurity will trigger a strong immune response and the vaccine will be attacked before it can function. In recent years, with the development of mRNA synthesis, chemical modification and delivery technology, the stability and translation efficiency of mRNA have been greatly improved. However, monitoring the quality of mRNA synthesis is still a key to the production process of mRNA vaccines. In this regard, the traditional nucleic acid electrophoresis method is relatively rough, and it is easy to degrade mRNA. A good choice would be to use Qsep series automatic nucleic acid fragment analyzer (Figure 3) to detect the distribution of nucleic acid fragments, with different detection fluxes, which can be flexibly applied to the detection needs of companies with different production scales.

Qsep series automatic nucleic acid fragment analyzer can quickly and efficiently complete the analysis of mRNA samples (Figure 4). The peak pattern can help users understand the quality of the samples at a glance. As shown in Figure 4(a), the main band is intact, and there is almost no degradation of mRNA. Figure 4(b&c) is an mRNA sample with severe degradation or synthesis problems. Qsep series software also has multiple sample peak map superposition and comparison (Figure 4 (D)), you can clearly analyze the differences in mRNA morphology under different synthesis methods.