Background/Objectives: Antigenic drift of influenza A(H1N1pdm09) viruses has led to periodic replacement of vaccine strains. Understanding how structural differences in glycoproteins influence immune protection is crucial for improving vaccine effectiveness. Methods: We conducted a structural analysis of the hemagglutinin (HA) and neuraminidase (NA) glycoproteins from drifted A(H1N1)pdm09 strains: A/South Africa/3626/2008 and A/Guangdong–Maonan/SWL1/2020, as well as their cold-adapted live attenuated vaccine (LAIV) reassortant strains (A/17/South Africa/2013/01(H1N1)pdm09 and A/17/Guangdong–Maonan/2019/211(H1N1)pdm09). We compared their replication in chicken embryo and mammalian cell culture, assessed type I interferon induction, and evaluated post-vaccine protection in mice after homologous and heterogeneous viral challenges. Results: The two vaccine strains had distinct glycosylation patterns for HA and NA. However, they had similar replication capacity in embryonated egg and mammalian cells. In the mouse respiratory tract, both strains replicated similarly. A/17/South Africa/2013/01(H1N1)pdm09 induced significantly higher levels of IFN-α and Mx1 in vitro, and it elicited earlier IgM and IgG response after vaccination in mice. At day 6 after immunization, it provided 70% protection from homologous challenge. A/17/Guangdong–Maonan/2019/211(H1N1)pdm09 did not prevent death, but it reduced viral titer in the lungs. Interestingly, A/17/South Africa/2013/01(H1N1)pdm09 provided full protection from heterologous H5N1 challenge, while A/17/Guangdong–Maonan/2019/211(H1N1)pdm09) only provided partial protection. Conclusions: Differences in HA and NA glycans among A(H1N1)pdm09 strains may influence innate and adaptive immunity, as well as cross-protection. These findings emphasize the importance of glycoprotein structure when selecting vaccine candidates for optimal homologous and cross-protection against influenza.

BACKGROUND: Live influenza vaccine strains may serve as a promising system for the delivery of target antigens to the body because such a vaccine is administered intranasally and stimulates multiple chains of immunity against both the target pathogen and the influenza virus, a serious infection that causes significant socioeconomic damage worldwide each year. AIM: The study was aimed to evaluate the biological properties of a recombinant live influenza vaccine strain of subtype A/H1N1pdm09 expressing a fragment of the Streptococcus pneumoniae Spr1875 surface protein. MATERIALS AND METHODS: The A/H1N1pdm09 recombinant live influenza vaccine strain expressing a 69-amino-acid fragment of the S. pneumoniae surface protein Spr1875 as part of a chimeric hemagglutinin molecule was prepared by reverse genetics using an 8-plasmid system. The reproductive activity of the recombinant virus was studied in chicken embryos, whereas immunogenicity and protective efficiency were studied in Balb/C mice. RESULTS: The recombinant influenza virus strain with hemagglutinin H1-Spr-69 demonstrated active reproduction in chicken embryos and retained the temperature-sensitive phenotypic trait of vaccine viruses. However, its growth in the respiratory tract of mice was limited compared with the original A/H1N1pdm09 vaccine virus. Intranasal administration of the recombinant H1-Spr strain to mice resulted in stimulation of virus-specific serum IgG antibody production comparable to that induced by the classic live influenza A/H1N1pdm09 vaccine. Furthermore, this strain induced an increase in IgG antibodies against the pneumococcal insertion Spr1875. Although the A/H1N1pdm09 variant was more effective than the chimeric H1-Spr virus in preventing weight loss in mice infected with mouse-adapted influenza A/California/07/09 (H1N1)pdm09 (H1N1)pdm09 virus, the titers of the challenge virus in the lungs of mice from both vaccine groups were significantly reduced compared with unvaccinated animals. CONCLUSIONS: The results demonstrate the ability of the chimeric recombinant H1-Spr strain to stimulate protective immunity against influenza virus.

Introduction : Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has undergone significant mutations since its emergence, resulting in a variety of antigenic variants. One of these variants is Omicron. Methods : In this study, the blood samples from 98 patients with acute coronavirus disease-19 (COVID-19) who were hospitalized during the initial SARS-CoV2 wave and the onset of Omicron infection in 2021 were analyzed. We used high-resolution melting (HRM) of PCR products to analyze RNA extracted from two clinical samples collected in July and November of 2021 from patients infected with the SARS-COV-2 virus. Results : HRM-analysis detected a characteristic deletion in the N-protein RNA of the virus isolated from November 2021 that is associated with the Omicron variant. Elevated levels of C-reactive protein (CRP), neutrophil-lymphocyte ratio (NLR), and interleukin-6 (IL-6) were observed in patients during both initial wave of COVID-19 and 2021 hospitalization. Additionally, complement levels were more frequently detected at the start of hospitalization during the second wave. IgG and IgM antibodies to SARS-CoV-2 were detected more often at the beginning of hospitalization during the second wave of COVID-19. During both outbreaks, an increase in hemagglutinin-inhibiting (HI) antibodies against Influenza A and B was observed in paired blood specimens from moderate to severe COVID-19 patients. Conclusions : Patients admitted during both waves of COVID-19 showed a significant rise in several inflammatory markers, suggesting that Omicron triggers significant inflammatory responses. The rapid formation of IgM and IgG in Omicron patients may indicate a faster immune response due to memory B cell formation after previous infections or vaccinations. Seasonal flu may negatively impact the clinical course of coronavirus infections. Further research is needed to determine if clinical presentation and laboratory parameters change in response to variations in the SARS-CoV virus in breakthrough cases and in patients with post-COVID syndrome.

BACKGROUND: Serum antibodies to SARS-CoV-2, when measured early after disease onset, may add value to the diagnosis of COVID-19. AIM: To examine the levels of serum antibodies to SARS-CoV-2 and laboratory blood parameters in hospitalized patients with COVID-19 of varying severity. MATERIALS AND METHODS: In this retrospective cohort study, we examined laboratory markers of inflammation in patients with acute COVID-19 during the 1st week of hospitalization. The levels of serum antibodies to SARS-CoV-2 were studied using commercial test systems. RESULTS: In 47% of hospitalized patients with COVID-19, during the first week of hospital stay, IgM and IgG antibodies to SARS-CoV-2 were detected, both in the case of a positive and negative PCR test. An average positive cor- relation of detected IgM and IgG with antibodies to the receptor-binding site of the S-protein of the SARS-CoV-2 virus is shown. In total, IgM and IgG antibodies to SARS-CoV-2 were most often detected in patients with a favorable course of the disease. Laboratory parameters in patients with moderate and severe COVID-19 were characterized by asignificant increase in the level of serum C-reactive protein, an increase in the neutrophil-leukocyte ratio and fibrinogen level, in comparison with data from patients with a mild course of the disease. In mild cases of infection, a moderately negative correlation was revealed between the levels of antibodies to SARS-CoV-2 and NLR. CONCLUSIONS: Detection of antibodies to SARS-CoV-2 in the early stages of hospitalization may be a predictor of a favorable outcome of the disease and serve as an additional criterion for the diagnosis of COVID-19 along with PCR analysis.

BACKGROUND: The live influenza vaccine is an effective means of combating influenza infection. It is characterized by ease of administration, cost-effectiveness, and rapid production, and it stimulates both systemic and local immune responses. This study investigates early protection against heterologous influenza infection within one week after immunization with the live influenza vaccine. AIM: The aim of the study was to experimentally investigate the mechanisms of early protection against heterologous influenza infection following immunization with a live influenza vaccine. MATERIALS AND METHODS: In in vitro experiments, we studied the production of type I interferons in a culture of monocyte-macrophage-derived cells using enzyme-linked immunosorbent assay. THP-1 cells were seeded at a concentration of 3 × 106 cells/ml, and after 48 hours, the vaccine strain of the live influenza vaccine was added. Mice were immunized intranasally under light ether anesthesia with the vaccine virus A/17/South Africa/2013/01(H1N1)pdm09, obtained from the virus collection of the Virology Department of the Institute of Experimental Medicine, at a dose of 6.0 lg EID50. Infection was performed on the 6th day after immunization with the virus A/Indonesia/5/2005(H5N1) IDCDC-RG2. RESULTS: During the introduction of both the vaccine virus and the parental virus A/South Africa/3626/2013 (H1N1)pdm09 into THP-1 cell cultures, an increase in the production of early cytokines was observed. Immunization with the live influenza vaccine completely protected the mice from lethal infection with a heterologous influenza virus. CONCLUSIONS: The obtained data may indicate the benefits of using the live influenza vaccine during the seasonal uptick of acute respiratory viral infections due to the stimulation of innate immune factors.

Introduction: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) underwent significant mutations, resulting in the Omicron variant. Methods: In this study, we analyzed blood samples from 98 patients with acute coronavirus disease 19 (COVID-19) hospitalized during the initial SARS-CoV-2 wave and the onset of Omicron in 2021. High-resolution melting (HRM) analysis of PCR products was used to analyze RNA extracted from clinical samples collected in July and November 2021 from patients infected with SARS-CoV-2. Results: HRM analysis revealed a characteristic deletion in the N protein RNA of the virus isolated in November 2021, associated with the Omicron variant. Elevated levels of inflammatory markers and interleukin-6 (IL-6) were observed in both waves of COVID-19. Complement levels and IgG and IgM antibodies to SARS-CoV-2 were detected more often during the second wave. An increase in hemagglutinin-inhibiting (HI) antibodies against influenza viruses was observed in paired blood specimens from moderate to severe COVID-19 patients during both outbreaks. Conclusions: Patients admitted during both waves of COVID-19 showed a significant rise in inflammatory markers, suggesting that Omicron triggers inflammatory responses. The rapid formation of IgM and IgG in Omicron may indicate a faster immune response. Seasonal flu may negatively impact the clinical course of coronavirus infections.