The new BCD-250 vaccine against coronavirus infection, which will be developed and tested by the biotech company Biocad(a participant of the Made in Russia project), will not cause any noticeable side effects, and besides, it can be easily adapted to fight new strains, the most dangerous at the moment.

The Made in Russia editorial board has learnt other details of the new pandemic vaccine which has no rivals anywhere in the world so far. Read this article to learn how BCD-250 differs from other vaccines, its features, advantages and trials.

WHAT IS BCD-250

BCD-250 is a modified recombinant vector based on the adeno-associated virus (rAAV), Biocad's press service explained. They carry the nucleotide sequence encoding a fragment of the Spike protein of the SARS-CoV-2 virus. This is the same protein that forms spike-like protrusions in the shell of the virus, forming its "crown". When the vaccine is injected intramuscularly, the vectors penetrate tissue cells, causing the body to produce antibodies to the secreted protein and form a sustained immune response that prevents the development of covid-19 disease caused by the virus.

UNLIKE OTHER VACCINES

It is believed that rAAV-based vectors are one of the safest systems for delivering genetic material into human cells because rAAVs are not linked to the pathogenesis of any disease. They are not incorporated into the human genome and are not capable of reproduction in the body or recombination with "wild-type" strains. The rAAV vectors are merely a protein envelope through which the nucleic acid encoding a fragment of the viral Spike protein enters cells. The vector DNA is present only in the cells where rAAV originally delivered it, and its lifespan is equal to that of the cell. Thus, the expression of the transgene delivered by the vector, a foreign DNA fragment, is time-limited, making the vaccine even safer.

The transgene itself has also been modified in the new vaccine. The Spike-protein fragment has been chosen so that most of the antibodies produced against it are neutralizing antibodies. In addition, the transgene was optimized, which resulted in a significant increase in its expression: the transgene is expressed 26 times stronger than the normal natural nucleotide sequence of this gene.

Gradually, antibodies to already registered vector vaccines (to vectors based on adenovirus Ad5 and Ad26) may appear. Antibodies against rAAV are also forming, but studies now show that their presence has no effect on immunization efficacy, and the number of antibodies to capsids - the protein envelope of the rAAV virus - falls very quickly, within two months. In other words, it can be assumed that the effectiveness of repeat vaccination with the new Biocad vaccine will not decrease, the company explained.

Biocad notes that vaccines based on this technology are not currently registered anywhere in the world.

OTHER ADVANTAGES OF THE NEW VACCINE

Firstly, BCD-250 should not cause side effects or they will appear in a very mild and mild form, the company said. Second, there is a chance that the immune system will "skip" the adeno-associated virus and focus entirely on fighting SARS-CoV-2 - which, in turn, will give more confident and sustained immunity.

In addition, the vaccine has another property: it's very easy to upgrade. This means that each new batch can be assembled as a "construction kit": each time "stitch" inside exactly the strain of coronavirus that is considered the most dangerous or most widespread at the moment. Thus, the new vaccine has already been optimized for the presence of the "delta" strain.

PRECLINICAL STUDY RESULTS

BCD-250 has already undergone pre-clinical trials, which have confirmed its effectiveness and safety. In particular, the studies have shown that immunization leads to formation of a large number of specific antibodies capable of neutralizing live SARS-CoV-2 virus. After vaccine administration, serum samples from experimental animals had a neutralizing capacity for SARS-CoV-2 at the same level, and in some cases even higher than serum samples from humans who had experienced the disease. A high antibody titer was achieved as early as day 21 after a single administration of the vaccine.

VOLUNTEER TESTING FOR THE VACCINE

Based on the results of the trials BCD-250 vaccine has been approved for clinical trials. The start is planned for 2021-2022 and recruitment of volunteers is expected to commence shortly. The volunteers will be vaccinated and monitored in two medical centres in St. Petersburg. The trials, as previously reported, will be completed by the end of 2026.

Biocad explained that the vaccine trial will last "as long as necessary": it is only necessary to obtain reliable data on the safety parameters and effectiveness of the "breakthrough" technology. The trials will be conducted as openly as possible, informing the scientific community of the results in real time and involving leading international specialists, they said.

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Author: Karina Kamalova