Influenza B viruses, divided into B/Victoria and B/Yamagata lineages, have not had B/Yamagata isolates after 2020. A study evaluated immunity to influenza B surface antigens hemagglutinin (HA) and neuraminidase (NA) in 138 patient sera from 2023 and 23 pairs of sera from 2018 to 2019 vaccine recipients. The phylogenetic tree of the influenza B virus, based on HA and NA genes, shows that the Yamagata lineage evolves gradually, while the Victoria lineage exhibits rapid mutations with short branches. In 2023, mean levels of antibodies to HA and NA of B/Yamagata virus were higher than to B/Victoria, despite no cases of B/Yamagata lineage isolation after 2020. The titers of antibodies to NA of B/Yamagata statistically significantly differed among individuals born before and after 1988. Among patients examined in 2018–2019, neuraminidase-inhibiting (NI) antibody titers before vaccination were higher to B/Yamagata than to B/Victoria, and NI antibodies to B/Victoria and B/Yamagata positively correlated with neutralizing antibodies to B/Victoria virus before and after vaccination. Immunity to B/Yamagata virus was stronger in 2023, despite no isolation since 2020, probably due to the presence of cross-reactive antibodies from B/Victoria infections or vaccinations. Antibodies to NA of B/Victoria and B/Yamagata in 2023 correlated significantly in patients born before 1988, potentially supporting the concept of ‘antigenic sin’ phenomenon for influenza B viruses. The fact that NI antibody titers to B/Victoria and B/Yamagata correlated with neutralizing antibody titers to B/Victoria may suggest broad cross-protection. Studying influenza B virus NA antigenic properties helps understand the evolution and antigenic competition of HA and NA.

BACKGROUND: Despite the continuing global spread of the coronavirus infection COVID-19 caused by the SARS-CoV-2 coronavirus, the mechanisms of the pathogenesis of severe infections remain poorly understood. The role of comorbidity with other seasonal viral infections, including influenza, in the pathogenesis of the severe course of COVID-19 remains unclear. MATERIALS AND METHODS: The present study used sera left over from ongoing laboratory studies of patients with varying degrees of severity of COVID-19. The study was approved by the Local Ethics Committee of the Federal State Budgetary Scientific Institution IEM (protocol 3/20 from 06/05/2020). We studied 28 paired samples obtained upon admission of patients to the hospital and after 57 days of hospital stay. Paired sera of patients with COVID-19 were tested for antibodies to influenza A and B viruses. The presence of IgG antibodies specific to the SARS-CoV-2 spike (S) protein was studied using an enzyme-linked immunosorbent assay (ELISA). The serum concentration of C-reactive protein and the neutrophil-lymphocyte ratio on the day of hospitalization were also assessed. RESULTS: At least a 4-fold increase in serum IgG antibodies to SARS-CoV-2 S protein was found both in patients with PCR-confirmed SARS-CoV-2 infection and without PCR confirmation. It was shown that out of 18 patients with moderate and severe forms of COVID-19 infection, six of them showed at least a 4-fold increase in antibodies to influenza A/H1N1, in one to influenza A/H3N2 and in two cases to the influenza B. Laboratory data in these two groups were characterized by significant increases in serum C-reactive protein and neutrophil-lymphocyte ratio concentrations compared with the moderate COVID-19 group. CONCLUSIONS: Serological diagnostics can additionally detect cases of coronavirus infection when the virus was not detected by PCR. In moderate and severe cases of COVID-19, coinfections with influenza A and B viruses have been identified. The results obtained confirm the need for anti-influenza immunization during the SARS-CoV-2 pandemic. Influenza virus screening can significantly improve patient management because recommended antiviral drugs (neuraminidase inhibitors) are available.

In this retrospective cohort study, we investigated the formation of individual classes of antibodies to SARS-CoV-2 in archived serial sera from hospitalized patients with the medium–severe (n = 17) and severe COVID-19 (n = 11). The serum/plasma samples were studied for the presence of IgG, IgM and IgA antibodies to the recombinant S- and N-proteins of SARS-CoV-2. By the 7th day of hospitalization, an IgG increase was observed in patients both with a positive PCR test and without PCR confirmation of SARS-CoV-2 infection. Significant increases in the anti-spike IgG levels were noted only in moderate COVID-19. The four-fold increase of IgM to N-protein was obtained more often in the groups with mild and moderate infections. The IgA levels decreased during the infection to both the S- and N-proteins, and the most pronounced decrease was in the severe COVID-19 patients. The serum IgG to S-protein one week after hospitalization demonstrated a high-power relationship (r_s = 0.75) with the level of RBD antibodies. There was a medium strength relationship between the levels of CRP and IgG (r_s = 0.43). Thus, in patients with acute COVID-19, an increase in antibodies can develop as early as 1 week of hospital stay. The SARS-CoV-2 antibody conversions may confirm SARS-CoV-2 infection in PCR-negative patients.

Aim: The objectives of our study were to evaluate a range of circulating biomarkers in COVID-19-related long-term neurological dysfunction. Methods: The study involved 30 patients with post-COVID syndrome (PCS) and 28 patients after COVID-19 without PCS. The third cohort consisted of 29 patients with acute COVID-19 of varying severity. The severity of COVID-19 was classified as mild and moderate to severe. The Montreal Cognitive Assessment (MOCA) and the SAGE test were used to study cognitive functions. The Hospital Anxiety and Depression Scale (HADS), the Sheehan Anxiety Scale, and the Beck Depression Inventory were used to study affective functions. The levels of serum cytokines and IgM, IgG, IgA to the SARS-CoV-2 coronavirus were determined using the Vector-Best test systems (Novosibirsk, Russia). We also studied the IgG subclasses to the spike protein of the SARS-CoV-2. Results: А mild to moderate COVID-19 infection primarily increases the risk of affective disorders and asthenia and, to a lesser extent, the development of cognitive impairment. The levels of IFN-α, IL-6, as well as serum antibodies to the SARS-CoV-2 among patients with PCS were significantly higher compared to convalescents without PCS. IgM to the SARS-CoV-2 was detected in the blood of patients with PCS during 2–7 months after the disease. After moderate and severe COVID-19, IgG2 and IgG4 were predominant in the blood of patients with PCS and neurological symptoms. The levels of IL-1, IL-4, IL-6, IL-8 in the blood serum of patients with PCS were higher after moderate and severe COVID-19 compared to patients who had mild COVID-19. Conclusions: The obtained data on an elevated level of cytokines and IFN-α in the blood of PCS patients can suggest the hypothesis about the participation of chronic inflammation in neurological disorders. The main limitation of the study is the relatively small sample size, which limits the statistical analyses.

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.