Prevalence and clinical impact of mono- and co-infections with endemic coronaviruses 229E, OC43, NL63, and HKU-1 during the COVID-19 pandemic.

Introduction: Endemic human coronaviruses (eHCoVs) are found worldwide and usually result in mild to moderate upper respiratory tract infections. They can lead to more severe illnesses such as croup, bronchiolitis, and pneumonia in vulnerable populations. During the coronavirus disease 2019 (COVID-19) pandemic, information on HCoV prevalence and incidence and clinical impact of co-infections of HCoV with SARS-CoV-2 was lacking. Objectives: Thus, this study aimed to determine the prevalence and clinical significance of infections caused by eHCoVs during the COVID-19 pandemic in Bulgaria. Methods: From January 2021 to December 2022, nasopharyngeal swabs of patients with acute upper or lower respiratory tract infections were tested for 17 respiratory viruses using multiplex real-time polymerase chain reaction assays. The clinical data and laboratory parameters of patients infected with respiratory viruses were analysed. Results: Of the 1375 patients screened, 24 (1.7 %) were positive for HCoVs, and 197 (14.3 %) were positive for eight other seasonal respiratory viruses. Five (0.7 %) of 740 patients positive for SARS-CoV-2 were co-infected with eHCoVs. Co-infected patients had a mean C-reactive protein level of 198.5 ± 2.12 mg/mL and a mean oxygen saturation of 82 ± 2.8 mmHg, while those in patients co-infected with SARS-CoV-2 and other respiratory viruses were 61.8 mg/mL and 92.8 ± 4.6 mmHg, respectively (p < 0.05). Pneumonia was diagnosed in 63.3 % of patients with HCoV infection and 6 % of patients positive for other seasonal respiratory viruses (p < 0.05). Patients with SARS-CoV-2 mono-infection stayed in hospital for an average of 5.8 ± 3.7 days, whereas the average hospital stay of patients with eHCoV and SARS-CoV-2 co-infection was 9 ± 1.4 days (p < 0.05). Conclusion: These findings indicate the low prevalence of eHCoVs and low co-infection rate between eHCoVs and SARS-CoV-2 during the COVID-19 pandemic in Bulgaria. Despite their low incidence, such mixed infections can cause severe signs that require oxygen therapy and longer hospital stays, underlining the need for targeted testing of severe COVID-19 cases to identify potential co-infections.

Predominance of influenza B/Yamagata lineage viruses in Bulgaria during the 2017/2018 season.

In this study, we investigated the antigenic and genetic characteristics of influenza viruses circulating in Bulgaria during the 2017/2018 season. The detection and typing/subtyping of influenza viruses were performed using real-time RT-PCR. Results of antigenic characterisation, phylogenetic and amino acid sequence analyses of representative influenza strains are presented. The season was characterised by the predominance of B/Yamagata viruses, accounting for 77% of detected influenza viruses, followed by A(H1N1)pdm09 (17%), B/Victoria (3.7%) and A(H3N2) (2.4%). The sequenced B/Yamagata, B/Victoria, A(H1N1)pdm09 and A(H3N2) viruses belonged to the genetic groups 3, 1A, 6B.1 and 3C.2a1, respectively. Amino acid analysis of B/Yamagata isolates revealed the presence of three changes in haemagglutinin (HA), eight changes in neuraminidase (NA) and a number of substitutions in internal proteins compared with the B/Phucket/3073/2013 vaccine virus. Despite the amino acid changes, B/Yamagata viruses remained antigenically related to the vaccine strain. B/Victoria isolates fell into a group of viruses with double deletion (Δ162-163) in HA1. Substitutions in HA and NA sequences of B/Victoria, A(H1N1)pdm09 and A(H3N2) viruses were also identified compared with the vaccine strains, including in antigenic sites. The results of this study confirm the genetic variability of circulating influenza viruses and the need for continual antigenic and molecular surveillance.

Age-specific differences in influenza virus type and subtype distribution in the 2012/2013 season in 12 European countries.

The epidemiology of seasonal influenza is influenced by age. During the influenza season, the European Influenza Surveillance Network (EISN) reports weekly virological and syndromic surveillance data [mostly influenza-like illness (ILI)] based on national networks of sentinel primary-care providers. Aggregated numbers by age group are available for ILI, but not linked to the virological data. At the end of the influenza season 2012/2013, all EISN laboratories were invited to submit a subset of their virological data for this season, including information on age. The analysis by age group suggests that the overall distribution of circulating (sub)types may mask substantial differences between age groups. Thus, in cases aged 5-14 years, 75% tested positive for influenza B virus whereas all other age groups had an even distribution of influenza A and B viruses. This means that the intepretation of syndromic surveillance data without age group-specific virological data may be misleading. Surveillance at the European level would benefit from the reporting of age-specific influenza data.

Rotavirus genotypes co-circulating in Europe between 2006 and 2009 as determined by EuroRotaNet, a pan-European collaborative strain surveillance network.

EuroRotaNet, a laboratory network, was established in order to determine the diversity of co-circulating rotavirus strains in Europe over three or more rotavirus seasons from 2006/2007 and currently includes 16 countries. This report highlights the tremendous diversity of rotavirus strains co-circulating in the European population during three years of surveillance since 2006/2007 and points to the possible origins of these strains including genetic reassortment and interspecies transmission. Furthermore, the ability of the network to identify strains circulating with an incidence of ≥1% allowed the identification of possible emerging strains such as G8 and G12 since the beginning of the study; analysis of recent data indicates their increased incidence. The introduction of universal rotavirus vaccination in at least two of the participating countries, and partial vaccine coverage in some others may provide data on diversity driven by vaccine introduction and possible strain replacement in Europe.

Molecular epidemiology of rotaviruses in Bulgaria: annual shift of the predominant genotype.

Rotavirus molecular epidemiology investigations provide important information about the incidence of rotavirus diseases and rotavirus strains in circulation in the prevaccine era. The purpose of this investigation was to study the burden of rotavirus disease, rotavirus strain diversity, and epidemiology specificities of rotavirus infections in Bulgaria. A total of 3,130 stools collected between 2005 and 2008 were tested by immune enzyme tests. G-P genotype identification of rotavirus strains were performed by reverse transcriptase polymerase chain reaction (RT-PCR). Rotavirus etiology was confirmed in 32.4% of the samples tested. Rotaviruses affected predominantly children under 5 years of age (95.5%), with a peak prevalence between the ages of 7 and 36 months. Four of the five globally distributed rotavirus strains (G1P[8], G2P[4], G4P[8], and G9P[8]) constituted 97.7% of all rotavirus strains in circulation. However, annual shifts of predominant rotavirus G-P genotypes were observed from season to season-G4P[8] was predominant in rotavirus season 2004/2005 (56.8%), but was replaced by G9P[8] in 2005/2006 (77.7%), and G2P[4] (41.6%) and G1P[8] (39.5%) in the following two consecutive rotavirus seasons. Year-round circulation of rotaviruses in the country with increased incidence in the winter-spring season and unexpected peaks preceding the rotavirus seasons were observed. Molecular epidemiology data are needed in Bulgaria for health policy makers in order to introduce routine rotavirus vaccination. The monitoring of rotavirus genetic diversity in Bulgaria in the postvaccination period will contribute to a successful rotavirus vaccination program.

Rotavirus surveillance in europe, 2005-2008: web-enabled reporting and real-time analysis of genotyping and epidemiological data.

BACKGROUND: The first European rotavirus surveillance network, EuroRotaNet, comprising 16 laboratories in 15 European countries, has been established. METHODS: Fecal samples from gastroenteritis cases positive for group A rotavirus antigen were collected from multiple European countries from 2005 to mid-2008 and were subjected to G and P genotyping. Epidemiological data collected included age, sex, geographical location, setting, dates of onset and sample collection, and clinical symptoms. RESULTS: A total of 8879 rotavirus-positive samples were characterized: 2129 cases were from the 2005-2006 season, 4030 from the 2006-2007 season, and 2720 from the ongoing 2007-2008 season. A total of 30 different G and P type combinations of strains circulated in the region from 2005 through 2008. Of these strains, 90% had genotypes commonly associated with human infections-G1P[8], G2P[4], G3P[8], G4P[8], and G9P[8]-and 1.37% represented potential zoonotic introductions. G1P[8] remained the most prevalent genotype in Europe as a whole, but the incidence of infection with G1P[8] rotavirus strains was <50% overall, and all 3 seasons were characterized by a significant diversity of cocirculating strains. The peak incidence of rotavirus infection occurred from January through May, and 81% of case patients were aged <2.5 years. Conclusions. Data gathered through EuroRotaNet will provide valuable background information on the rotavirus strain diversity in Europe before the introduction of rotavirus vaccines, and the network will provide a robust method for surveillance during vaccine implementation.

[A thromboelastographic method of determining the antiaggregation activity of the vascular wall]. / Tromboélastograficheskii metod otsenki antiagregatsionnoi aktivnostisosudistoi stenki.

Thromboelastography was used for the assessment of the vascular wall antiaggregation function; this function was determined as the activity of prostacyclin, synthesized and released by the vascular wall after local ischemia of the limb vessels, antiaggregatory towards the blood platelets. This method permits a rapid and easy objective assessment of the vascular wall antiaggregation function and gives information on the role of the blood ingredients, the prostacyclin activity contributing to their effect.

[Biological activity of human alpha-interferons studied using specific antisera]. / Issledovanie biologicheskoi aktivnosti chelovecheskikh al'fa-interferonov pri pomoshchi spetsificheskikh antisyvorotok.

Preparation of highly active rabbit antisera (AS) to human recombinant alpha 2-interferon and their use for studying biological properties of natural and plasmid alpha-interferons are described. By exhaustion of AS by alpha 3-interferon there were prepared practically monospecific AS not reacting with antigenic determinants of alpha 3-interferon. It was found that alpha 3-interferon represented a significant portion of human lymphoblastoid interferons and was included in PH-labile alpha-interferon from serum of patients with Kaposi carcinoma. AS to alpha 2-interferon completely neutralized antiviral and antiproliferative activity of the homologous subtype alpha-interferon and stimulation of cytotoxicity of human natural killer cells induced by it. It neutralized also the same effects of the heterologous subtypes (alpha 3 and alpha F/D) and leukocytic interferon, but the neutralization level was lower. The results of the study confirmed the polyfunctional nature of the interferon molecule.

[The search for preparations suppressing the reproduction of the AIDS virus]. / Poisk preparatov, podavliaiushchikh reproduktsiiu virusa SPID.

Trials of clinically advantageous national inducers, thymus hormones, as well as human recombinant alpha 2-interferon were carried out in cultures of continuous lymphoblastoid cells H9/IIIB infected with HIV virus. The virus-inhibiting effect for HIV was observed with interferon in doses of 10-100 IU/ml. At a concentration of interferon of 1000 IU/ml, virus replication was inhibited completely, the interferon doses used exerting no marked toxic or antiproliferative effect on the cells. Human interferon inducers, poly(G).poly(C), PXL-6, dsRNA in concentrations of 50-100 micrograms/ml inhibited virus reproduction significantly. The highest antiviral effect was achieved with yeast dsRNA. The preparations of immunomodulators, thymarin, the 5th and 7th fractions of thymosin, noticeably stimulated proliferation of infected T-lymphocytes, reducing the relative number of cells carrying the virus-specific antigen. Combined use of preparations with different mechanisms of the antiviral effect may be advantageous in prevention and treatment of AIDS.

[Testing of monoclonal antibodies to human interferon]. / Testirovanie monoklonal'nykh antitel k chelovecheskomu interferonu.

A comparative study of testing methods for polyclonal and monoclonal antibodies to human interferon using direct and reverse neutralization of the antiviral activity of interferon as well as ELISA was carried out. The activity of antibodies in ELISA was dozens of times higher than in neutralization tests. Polyclonal antibodies from the sera of mice immunized with alpha 2 interferon had a higher neutralizing capacity. M-5 monoclonal antibodies in specimens of ascitic fluid induced by inoculation of mice with hybrid cells exhibited an increase in both binding and neutralizing activity as compared with specimens of the culture fluid. Immunoglobulins from the ascitic and culture fluid of nonproductive myeloma cells as well as hybridomas producing monoclonal antibodies of other specificities showed practically no reaction with interferon in any of the tests under study. The screening of monoclonal antibodies intended for research and biotechnological purposes requires a composite analysis in both neutralization and binding tests in order to recover purposefully the hybrid clones producing antibodies with both or one of these properties.