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.

[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.