US, WASHINGTON (ORDO NEWS) — A group of scientists from the Beijing Institute of Microbiology and Epidemiology has created a new strain of coronavirus SARS-CoV-2 (pathogen Covid-19), which is able to effectively infect laboratory mice. As explained in a study published on bioRxiv’s preprint site , the new version of SARS-CoV-2 will help speed up the testing of vaccines that hundreds of scientists around the world are working on quickly and easily.
“In order to develop safe and effective vaccines, suitable animal-tested models must be created. We report the rapid adaptation of SARS-CoV-2 in mice of the inbred line BALB / c (one of the most popular genetic lines of laboratory mice is albino and immunodeficiency. – Ed.) , On the basis of which a convenient, economical, and efficient system was developed testing [vaccines] in animals. In particular, we found that the MACSp6 strain adapted to mice effectively infected both elderly and young individuals, which led to the development of moderate pneumonia in them, as well as to inflammatory reactions, ”the biologists write.
Earlier studies, scientists explain, showed the possibility of breeding transgenic mice that have the human ACE2 receptor and are thus able to become infected with coronavirus, but on an “industrial scale” this takes a lot of time. In addition, the disease in the body of such rodents proceeds in an extremely weakened form: inflammatory reactions are weak, as well as damage to the lungs. However, a new study found that ordinary laboratory mice infected with the new MASCp6 strain exhibited acute and moderate inflammatory reactions with macrophage infiltration in the lungs and elevated levels of some inflammatory cytokines.
“Small animal models, such as mice, provide reliable and convenient approaches for evaluating the in vivo effectiveness of antiviral countermeasures, including vaccines and prophylactic / therapeutic agents. However, ordinary mice are generally not susceptible to infection with human coronaviruses using their proteins as receptors. For example, MERS-CoV (a causative agent of the Middle East respiratory syndrome. – Ed.) Does not infect wild mice, but infects rodents expressing the membrane enzyme dipeptidyl peptidase-4 (DPP4). <…> At the same time, a small number of transgenic mice that could be infected with SARS-CoV-2, as well as associated costs, including maintenance, seriously complicated the development of a vaccine against Covid-19, ”the authors add.
The increased infectivity of MACSp6 — the parasitic microorganism’s ability to survive in the host organism — was explained in the mice participating in the study by replacing the key residue (N501Y) in the receptor-binding domain (RBD) of the S-protein that covers the viral particle membrane (another group of scientists found earlier that RBD the SARS-CoV-2 viral protein domain has evolved to interact most effectively with ACE2 on the surface of the host cells). Thus, the coronavirus variation acquired the ability to infect laboratory animals in just six transitions between their generations.
Then, Chinese biologists, using their new model in laboratory animals, in vivo evaluated the effectiveness of an experimental subunit vaccine (an immunogenic drug that is a chemical component that is removed from the structure of a microbial cell or virus; subunit vaccines can contain nucleic acids isolated from the structure of a microbial cell (DNA or RNA), ribosomes, proteins, lipopolysaccharides, glucidolipoprotein complexes containing a protective antigen) based on the RBD domain.
The results of the experiment showed that the drug caused potent neutralizing antibodies and provided complete protection against infection with the MACSp6 version without detectable viral RNA in the lungs and trachea. As biologists emphasized, their vaccine “based on RBD has great prospects for the further development and prevention of the Covid-19 pandemic.” However, it is worth recalling that this work has yet to undergo peer review, so it is too early to draw far-reaching conclusions.
Earlier, American experts presented a review study on the most promising methods of combating coronavirus, and their colleagues from Russia suggested using a thrombolytic drug to treat complications of Covid-19.
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