Background Research in the subject of the influence of SARS-CoV-2 mechanisms on human’s homeostasis remains actual problem. Particular interest is the study of pathomorphological changes in the appendix in children with COVID-19. Objectives Aim of the study: morphological and molecular biological evaluation of the appendix in children of different age groups with COVID-19. Methods Groups were formed on the basis of anamnestic, clinical and morphological data: I (n = 42; aged 2 to 18 years, average - 10.8 years) – with an established clinical diagnosis: coronavirus infection (COVID-19; PCR+); II (n = 55; aged 2 to 18 years, average - 9.7 years) – with a confirmed clinical diagnosis of acute appendicitis; collected before the onset of the COVID-19 pandemic in 2017-2019; III (n = 38; aged 2 to 18 years, average - 10.3 years) - control group. Histological and immunohistochemical studies were conducted using primary antibodies to CD3, CD4, CD68, CD163, CD20, CD138 and to pro-inflammatory (IL-1, IL-6) and anti-inflammatory (IL-4, IL-10) cytokines. Results In most samples of appendix in children with COVID-19 were discovered signs of destructive phlegmonous-ulcerative and gangrenous appendicitis. An increase in CD3+, CD4+, CD68+, CD163+, CD20+ CD138+ immunocompetent cells was found in the appendix of children with COVID-19. As well, there is an increase in pro-inflammatory (IL-1, IL-6) and anti-inflammatory (IL-4, IL-10) cytokines. Conclusions The aforementioned pathological and immunohistochemical changes were more pronounced in the group of children aged 6-12 years (childhood).

Development of new techniques of multimodal treatment, diagnostics of various neoplasms and improvement of these techniques can significantly increase the life expectancy of patients with carcinomas of the colon and abdominal cavity organs, since prevention of various side effects of radiation therapy is one of the main problems of oncological care. Electron irradiation is one of the most promising types of radiation therapy. There are no data on proliferation and apoptosis of the colon epithelium after irradiation with electrons, especially in different modes (single and summary). Aim of the study: Morphological evaluation of apoptosis and proliferation of colonic epithelium after local irradiation with electrons at doses 2 Gy and 25 Gy. Materials and methods. Colon fragments from sexually mature Wistar rats (n=50, body weight 200 ± 10 g) were divided into three groups: I - control (n = 10); II - experimental group (n = 20; local single electron irradiation at a dose of 2 Gy), III - experimental group (n=30), local fractional irradiation with electrons at a total dose of 25 Gy. They were studied by light microscopy using hematoxylin and eosin staining and immunohistochemical reactions with antibodies to Ki-67 and Cas3. Morphological disorders were accompanied by increased expression of pro-apoptotic molecules (caspase-3), and the period of regeneration by proliferative marker (Ki-67). Conclusions: Local fractional irradiation of the colon with electrons at a dose of 2 Gy and 25 Gy resulted in minor changes in the epithelium, a decrease in the number of goblet cells, but with preservation of regenerative potential, mild degenerative-dystrophic lesions. Intestinal crypts were damaged, leading to a decrease in Ki-67 and an increase in the number of caspase-3-positive epitheliocytes.

A new variant of the SARS-CoV-2 Omicron BA.5 virus has displaced all previous variants of the virus around the world. Preliminary assessment of the effectiveness of drugs for the prevention and treatment of COVID-19 requires the availability of infection models in animals. In this study, we characterize the infection model SARS-CoV-2 Omicron BA.5 and its progeny sublineage BE.1 in hACE2-transgenic mice and in Syrian hamsters. Both sublineages turned out to be pathogenic for animals – the challenged animals showed weight loss, a high level of viral load and acute inflammation in the lungs. Part of BA.5-infected mice died after virus challenge, indicating that this virus variant is more pathogenic than the previous BA.1 variant but less pathogenic than Wuhan variant.