Corrigendum to "Assessment of trivalent live influenza vaccines in MDCK cell line" [MethodsX 8 (2021) 101442].

[This corrects the article DOI: 10.1016/j.mex.2021.101442.].

Assessment of trivalent live influenza vaccines in MDCK cell line.

We applied a one-step reverse transcriptase real-time PCR (rRT-PCR) analysis using TaqMan technique to evaluate the infectious titers of vaccine strains containing in trivalent live influenza vaccines (LAIVs). The cold-adapted reassortant influenza viruses A/H1N1 pdm09, A/H3N2, B/Yamagata and B/Victoria, included in the composition of the LAIV in 2015-2016, 2017-2018 and 2018-2019 flu season were studied for reproductive activity in MDCK cells as part of a mono-vaccine and tri-vaccine. For this we have developed a set of specific primers and probes. Method validation was performed using ELISA-test after mouse monoclonal antibodies to hemagglutinin (HA) staining of MDCK monolayer. Influenza B viruses B/Yamagata and B/Victoria were studied in MDCK cells in mono-infection and coinfection with different multiplicity of infection (MOI) using quantitative rRT-PCR.•RT-PCR analysis was adjusted to assess the growth characteristics of cold-adapted reassortant influenza viruses in MDCK cell line. The greatest suppression in the composition of the tri-vaccine was exposed to the H1N1 pdm09 LAIV component.•Influenza B viruses are least suppressed in trivalent LAIV. Influenza viruses B/Yamagata and B/Victoria reproduced as part of a mixed preparation not lower, if not better than as a mono-preparation at an MOI of 0.1. At an MOI of 0.01, the reproduction of both B/Yamagata and B/Victoria in the mixture was reduced compared to mono-vaccine.•The interference of trivalent LAIV vaccine viruses in MDCK cells was minimal at low dilutions. This indicates that it is undesirable to reduce the titers of vaccine viruses, including at the stages of transportation and storage of LAIV.

Evaluation of influenza A and B cold-adapted reassortant virus reproduction in trivalent live influenza vaccines.

BACKGROUND: The objective of the present study was to compare reproduction of trivalent LAIV vaccine strains in MDCK cells and to perform quantitative RT-PCR analysis of trivalent LAIV replication after inoculation in mice. METHODS: We applied a reverse transcriptase real-time PCR (rRT-PCR) analysis using TaqMan technique to evaluate the infectious titers of vaccine strains containing in trivalent live influenza vaccines (LAIVs). We confirmed the PCR data in ELISA using staining of MDCK monolayer with mouse monoclonal antibodies to hemagglutinin. RESULTS: The viral load during the reproduction of mono-vaccines and trivalent LAIV in MDCK cells was similar at low dilutions. The content of vaccine viruses was evaluated using quantitative RT-PCR analysis in the nasal turbinate and lungs of CBA mice on day 3 after intranasal immunization. It was shown that despite the almost complete absence of reproduction of the A/H3N2 virus in mice, the immune response of A/H3N2-specific antibodies was formed at the same level as to other viruses. In MDCK cells, a decreased infectious titers of vaccine viruses in trivalent LAIV compared to mono-vaccines was demonstrated except for B/Yamagata virus. CONCLUSION: RT-PCR analysis is applicable to assess the growth characteristics of cold-adapted reassortant influenza viruses in vitro and in mice. The interference of trivalent LAIV vaccine viruses in MDCK cells was minimal at low dilutions. In mice, decrease in infectious titers did not lead to a decline of the immunogenicity.

Anti-Influenza Activity of Enterocin B In vitro and Protective Effect of Bacteriocinogenic Enterococcal Probiotic Strain on Influenza Infection in Mouse Model.

In spite of scientific evidence demonstrating the antiviral activity of lactic-acids bacteria, little is known about the mechanism of their action. Previously, several bacteriocins isolated from lactic acid bacteria (LAB) and some other microorganisms were reported as having antiviral activity in vitro. In the present study, chemically synthetized enterocin B (EntB) and the strain E. faecium L3, known as the producer of this peptide, were tested for activity against influenza viruses. The inhibition of cytopathic effect of А/Perth/16/2009(H3N2) and A/South Africa/3626/2013(H1N1) pdm influenza viruses in MDCK cells by chemically synthetized EntB was revealed. The EntB demonstrated antiviral activity at a concentration of 2.5-5 µg/ml depending on the dose of viruses. This peptide exhibited low toxicity in MDCK cells, causing partial damage of the monolayer of the cells only at a concentration above 10 µg/ml. It was also shown, that strain E. faecium L3-protected mice from lethal A/South Africa/3626/2013(H1N1) pdm infection. We speculate that this protective effect of enterococci may be associated with the specific action of enterocin B, which possesses antiviral activity in vitro.