[Comparative study of Wuhan-like and omicron-like variants of SARS-CoV-2 in experimental animal models].

INTRODUCTION: The variability of SARS-CoV-2 appeared to be higher than expected, the emergence of new variants raises concerns. The aim of the work was to compare the pathogenicity of the Wuhan and BA.1.1/Omicron variants in BALB/c mice and Syrian hamsters. MATERIALS AND METHODS: The study used strains of SARS-CoV-2: Dubrovka phylogenetically close to Wuhan-Hu-1, and LIA phylogenetically close to Omicron, BALB/c mice, transgenic mice B6.Cg-Tg(K18-ACE2)2Prlmn/HEMI Hemizygous for Tg(K18-ACE2)2Prlmn, Syrian golden hamsters. Animals were infected intranasally, pathogenicity was estimated by a complex of clinical, pathomorphological and virological methods. RESULTS: Comparative studies of SARS-CoV-2 Dubrovka and LIA strains on animal models demonstrated their heterogeneous pathogenicity. In parallel infection of BALB/c mice with Dubrovka and LIA variants, the infection proceeded without serious clinical signs and lung damage. Infection with the LIA strain resulted to a systemic disease with a high concentration of viral RNA in the lungs and brain tissues of animals. The presence of viral RNA in mice infected with the Dubrovka strain was transient and undetectable in the lungs by day 7 post-infection. Unlike the mouse model, in hamsters, the Dubrovka strain had a greater pathogenicity than the LIA strain. In hamsters infected with the Dubrovka strain lung lesions were more significant, and the virus spread through organs, in particular in brain tissue, was observed. In hamsters infected with the LIA strain virus was not detected in brain tissue. CONCLUSION: The study of various variants of SARS-CoV-2 in species initially unsusceptible to SARS-CoV-2 infection is important for monitoring zoonotic reservoirs that increase the risk of spread of new variants in humans.

Generation of SARS-CoV-2 Mouse Model by Transient Expression of the Human ACE2 Gene Mediated by Intranasal Administration of AAV-hACE2.

One of the most important steps in the development of drugs and vaccines against a new coronavirus infection is their testing on a relevant animal model. The laboratory mouse, with well-studied immunology, is the preferred mammalian model in experimental medicine. However, mice are not susceptible to infection with SARS-CoV-2 due to the lack of human angiotensin-converting enzyme (hACE2), which is the cell receptor of SARS-CoV-2 and necessary for the entry of the virus into the cell. In present work, it was shown that intranasal administration of the adeno-associated vectors AAV9 and AAV-DJ encoding the hACE2 provided a high level of expression of ACE2 gene in the lungs of mice. In contrast, the introduction of the AAV6 vector led to a low level ACE2 expression. Infection with SARS-CoV-2 of mice expressing hACE2 in the lungs led to virus replication and development of bronchopneumonia on the 7th day after infection. Thus, a simple method for delivering the human ACE2 gene to mouse lungs by intranasal administration of the AAV vector has been proposed. This approach enabled rapid generation of mouse model for studying coronavirus infection.

[Generation of SARS-CoV-2 Mouse Model by Transient Expression of the Human ACE2 Gene Mediated by Intranasal Administration of AAV-hACE2].

One of the most important steps in the development of drugs and vaccines against a new coronavirus infection is their testing on a relevant animal model. The laboratory mouse, with well-studied immunology, is the preferred mammalian model in experimental medicine. However, mice are not susceptible to infection with SARS-CoV-2 due to the lack of human angiotensin-converting enzyme (hACE2), which is the cell receptor of SARS-CoV-2 and necessary for the entry of the virus into the cell. In present work, it was shown that intranasal administration of the adeno-associated vectors AAV9 and AAV-DJ encoding the hACE2 provided a high level of expression of ACE2 gene in the lungs of mice. In contrast, the introduction of the AAV6 vector led to a low level ACE2 expression. Infection with SARS-CoV-2 of mice expressing hACE2 in the lungs led to virus replication and development of bronchopneumonia on the 7th day after infection. Thus, a simple method for delivering the human ACE2 gene to mouse lungs by intranasal administration of the AAV vector has been proposed. This approach enabled rapid generation of mouse model for studying coronavirus infection.

Efficacy of (R)-6-Adamantane-Derivatives of 1,3-Oxazinan-2-One and Piperidine-2,4-Dione in The Treatment of Mice Infected by the A/California/04/2009 influenza Virus.

The World Health Organization (WHO) recommends antivirals as an additional line of defense against influenza. One of such drugs is rimantadine. However, most of the circulating strains of influenza A viruses are resistant to this drug. Thus, a search for analogs effective against rimantadine-resistant viruses is of the utmost importance. Here, we examined the efficiency of two adamantane azaheterocyclic rimantadine derivatives on a mouse model of pneumonia caused by the rimantadine-resistant influenza A virus /California/ 04/2009 (H1N1). BALB/c mice inoculated with the virus were treated with two doses (15 mg and 20 mg/kg a day) of tested analogs via oral administration for 5 days starting 4 hours before the infection. The efficacy was assessed by survival rate, mean day to death, weight loss, and viral titer in the lungs. Oral treatment with both compounds in both doses protected 60-100% of the animals, significantly increased the survival rate, and abolished weight loss. The treatments also inhibited virus titer in the lungs in comparison to the control group. This treatment was more effective compared to rimantadine at the same scheme and dosage. Moreover, the study of the sensitivity of the virus isolated from the lungs of the treated mice and grown in MDCK cells showed that no resistance had emerged during the 5 days of treatment with both compounds.

[Vaccination with virus-like particles containing hemagglutinin protects the lungs of mice with postifluenza bacterial pneumonia: virological, microbiological and clinical data].

INTRODUCTION: Influenza is a severe viral disease, a frequent complication of which is a secondary bacterial pneumonia. Influenza vaccines prevent secondary bacterial complications. Virus-like particles are one of the promising areas for the development of new vaccines. The aim of this work is to study the correlation of the pathomorphological characteristics of the lungs with clinical, virological, and microbiological markers of the disease at vaccination with virus-like particles (VLPs), containing hemagglutinin (HA) of influenza virus (HA-Gag-VLPs) in a murine model of secondary bacterial pneumonia induced by S. pneumoniae after influenza infection. MATERIAL AND METHODS: BALB/c mice were vaccinated with VLPs containing influenza HA. After 21 days, mice were infected with two strains of influenza viruses, homologous and non-homologous, and 5 days after viral infection, were infected with S. pneumoniae. The vaccination effect was evaluated by morphological, virological (titer of the virus in the lungs) and microbiological (titer of bacteria in the lungs) data, and was confirmed by clinical data (survival, change in body weight). RESULTS: Immunization with HA-Gag-VLPs, followed by infection with a homologous influenza virus and S. pneumoniae, reduced the area of foci of inflammation, inhibited the replication of the virus and bacteria in the lungs, and also protected animals from death and reduced their weight loss. Immunization with HA-Gag-VLPs upon infection with a heterologous strain and S. pneumoniae did not affect these criteria. CONCLUSION: The immunization with HA-Gag-VLPs prevented the viral replication, providing a reduction of S. pneumoniae titer and the degree of lung damage, protecting animals from the disease in a murine model of secondary bacterial pneumonia, induced by S. pneumoniae, after influenza infection with homologous strain of the virus.