Monkeys vaccinated against coronavirus
Experimental vaccine protects macaques from coronavirus pneumonia
With the help of an experimental vaccine, molecular biologists have protected macaques from pneumonia, which could develop as a result of infection with a new type of coronavirus. Preliminary results of their work are published in the electronic scientific library bioRxiv (van Doremalen et al., ChAdOx1 nCoV-19 vaccination prevents SARS-CoV-2 pneumonia in rhesus macaques).
"A single dose of the ChAdOx1-nCoV-19 vaccine protected macaques from pneumonia and lung tissue damage associated with coronavirus infection after we injected a large dose of the SARS-CoV-2 virus into their body," the scientists write.
In recent months, scientists from different countries have developed and started testing a new type of coronavirus vaccine. Some of them are tested in experiments on animals, others on volunteers. The first results of the tests, as scientists expect, will be known only in about a year and a half, if the method of testing vaccines does not change.
Many of these drugs are based on untested technology by which scientists inject RNA fragments into human cells and force them to produce large amounts of virus proteins. Classical inactivated and recombinant vaccines based on weakened viral particles and finished fragments of the virus envelope are also being developed. In both cases, it will be very difficult to mass produce these drugs, and there are no guarantees of their success yet.
One of the vaccines – ChAdOx1-nCoV-19 – is being developed by molecular biologists and physicians from the US National Institutes of Health and Oxford University (UK) under the guidance of Professor Sarah Gilbert. The basis for its development was the ChAdOx1-MERS viral vaccine, which British scientists created to combat Middle Eastern MERS fever, the causative agent of which is a close relative of the SARS-CoV-2 coronavirus.
Pioneer Monkeys
The vaccine is a chimpanzee adenovirus – a relatively safe pathogen for humans that can penetrate into their cells, but not multiply in them. Scientists have modified the structure of its genome so that it forces the human body to produce a large number of copies of one of the key proteins of the SARS-CoV-2 envelope, which help the immune system to recognize real viral particles.
After testing its work on mice, the scientists moved on to experiments on rhesus monkeys (Macaca mulatta). Previous studies have shown that these primates carry coronavirus infection in the same way as humans, so testing vaccines on Rhesus will be more effective than on other animals.
Scientists injected six primates with a small amount of ChAdOx1-nCoV-19, waited for an immune response to form (this happens after about 2-4 weeks), and then tried to infect them with the real coronavirus SARS-CoV-2.
As these experiments showed, the vaccine completely protected the monkeys: the virus could not get into their lungs and they did not get pneumonia. On the other hand, it did not prevent SARS-CoV-2 from infecting the cells of the nasal mucosa of primates. However, scientists are not sure whether the virus could effectively reproduce there, since there were quite a few fragments of viral RNA in the upper respiratory tract of macaques.
It is important that scientists have checked the consequences of repeated contact of monkeys with the virus. These experiments showed that vaccination did not make their immunity an "accomplice" of SARS-CoV-2 and did not cause an excessively violent immune reaction that could potentially kill animals or people. Thanks to this, scientists have started the first phase of clinical trials. Gilbert and her colleagues hope that if the tests are completed quickly, they will be able to begin more extensive testing of the vaccine on volunteers.
"The successful completion of these experiments on primates allowed us to begin conducting the first phase of clinical trials on volunteers on April 23. By May 13, more than a thousand British residents had participated in them. Therefore, we can say with confidence that our experiment was an important step towards creating an effective and safe vaccine against COVID-19," the biologists concluded.
It should be added that the scientists' article was not reviewed by independent experts and editors of scientific journals, as is usually the case in such cases. Therefore, conclusions from it and similar articles should be treated with caution.
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