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Community-acquired pneumonia is a polyetiological infectious disease of bacterial or viral nature. In most cases, it is caused by pathogens such as Streptococcus pneumoniae, Mycoplasma pneumoniae, Haemophilus influenzae, Chlamydophila pneumoniae, Staphylococcus aureus, Legionella spp. However, despite that a wide range of modern diagnostic methods have been introduced into laboratory practice, the etiology of the disease can be determined only in 40–60% of cases. Here, we analyzed the causative agents of community-acquired pneumonia and relevant markers samples of clinical material collected from patients undergoing treatment in the medical facilities of the city of Saratov and the Saratov Region during the period from July to August, 2020, coupled to increase number of cases of new coronavirus infection COVID-19. Clinical material (oropharyngeal swabs, saliva, sputum, blood and blood serum) was obtained from 129 patients and investigated by using microbiological, immunoserological and molecular genetic methods. For this, there were used transport and nutrient media, diagnostic drugs, reagents, discs with antibacterial domestic and foreign drugs registered in the Russian Federation. As a result, 82 (63.6%) patients were found to have markers of the pathogen COVID-19 (viral RNA or specific antibodies of IgM and/or IgG classes), whereas 42% of cases had overlapped RT-PCR and ELISA data. There was a predominance of severe clinical forms of the disease in the group of patients with pneumonia caused by SARS-CoV-2 virus (17.1%), compared with pneumonia of another etiology (12.8%). No marked differences in specific pattern of the accompanying microflora and its sensitivity to antibacterial agents were observed in persons with/without markers of COVID-19. While being examined by bacteriological methods, S. aureus, K. pneumoniae, S. pneumoniae, M. pneumoniae, Acinetobacter spp., both in monoculture and in associations, were isolated from samples of clinical material collected from the majority of patients. In 49.6% of cases, pathogenic microflora, including pathogens causing community-acquired pneumonia, has not been identified, which may be due to the use of antibacterial drugs before the collection of clinical material and treatment applied due to comorbid chronic diseases.

In theRussian Federation, Y. pestis NIIEG strain-based live attenuated vaccine is used for immunization against plaque on epidemiological indications, displaying high efficiency. However, individual fluctuations in adaptive immunity after vaccination necessitate conducting a search for genes underlying variability of developing immune response. Of note, HLA (Human Leukocyte Antigen) gene polymorphism plays an important role in this process. In our study, we identified HLA class II haplotypes for HLA-DRB1, HLA-DQA1, and HLA-DQB1 in 120 residents of theterritoryofPre-Caspiannatural plague focus, who were immunized against plague. In addition, level of TNFα production correlated with detecting allelic groups HLA-DRB1*04 (р = 0.05) and DRB1*12 (р = 0.01). The data obtained show that HLA class II gene polymorphism can affect the level of cytokine secretion in response to plague immunization. Examining the genes regulating immune factor production will allow to get better insight into the mechanisms underlying immune response variations after vaccination as well as contribute to predicting immunogenicity and efficiency of developing vaccine preparations.

At present, the search for biomarkers, which indicate the presence of tense antiplague immunity, is continuing. The aim of the study was to determine the parameters of cellular and humoral immunity in persons vaccinated with the plague vaccine according to epidemiological indications and to characterize the correlation interrelations between them in the dynamics of the antiplague response formation. Blood samples from 114 people living in the territory of the Pre-Caspian sandy natural plague foci were investigated. Using commercial kits, the production of cytokines IL-1 β , IL-2, IL-4, IL-6, IL-8, IL-10, IL-18, IFN γ , TNF α (Vector-Best, Russia) IL-17A (eBioscience, Austria), immunoglobulins IgG, IgM, IgA (Vector-Best, Russia) was determined on the enzyme immunoassay analyzer LAZURIT (Dynex Technologies, США ). Blood leukocyte immunophenotyping was carried out using f luorochrome-labeled monoclonal antibodies Cyto-Stat CD45-FITC, CD4-PE, CD8-ECD, CD3-PC5 (Beckman Coulter, США ) on the CyAn ADP DakoCytomation f low cytometer (Denmark). Obtained data analysis revealed a number of differences in the production of detectable cytokines (TNF α , IL-1 β , IL-2, IL-4, IL-6, IL-17) between groups of vaccinated and first-vaccinated people. However, human blood cells, regardless of the multiplicity of the graft, retained their functional reactivity and were able to actively secrete the majority of the analyzed cytokines (8 of 10) in response to stimulation with concanavalin A. Diagnostically significant changes in the concentration of IFN γ , TNF α and IL-4 were detected for the characteristics of a specific antiplague response. For these marker cytokines, the greatest number of correlations have been revealed, both with each other and with changes in the level of other parameters: cytokines, immunoglobulins, T cells. The revealed multiple correlation links between the cytokine and immune status indices indicate the activation of both the cellular and humoral components of the antiplague immune response. The informative value of the complex analysis application of correlation interrelations between the humoral and cellular immunity parameters is shown to assess the level of immunological efficacy (actual vaccination) of vaccination in persons vaccinated against plague.