Evolution of influenza viruses based on sensitivity to temperature of replication

Introduction. The assessment of the ability of influenza viruses to replication at temperature conditions beyond optimal values approaches us to understanding the laws of their evolutionary variability. The temperature range for the reproduction of epidemic viruses is also an important indicator for choosing a rational strategy for producing attenuated reassortants for a live influenza vaccine. The purpose of the study is a retrospective analysis of the biological properties of influenza viruses from various pandemic and epidemic cycles based on their ability to replicate at temperatures beyond optimal values. Materials and methods . We studied 234 strains of human influenza A and B viruses that caused epidemics in the 20 th – 21 st centuries. The infectious activity of viruses at different incubation temperatures was determined in developing chicken embryos. The temperature sensitivity and cold resistance of viruses replication were estimated as a difference of infectious titers at the optimum and raised or lowered incubation temperatures. Results . Data from a retrospective study indicate that the range of sensitivity to replication temperature during the natural drift of influenza A and B pathogens is subject to regular variability that has a cyclic character. Discussion. To assess the evolution and epidemic potential of influenza viruses, it is important not only to register a change in their antigenic properties but also to take into account the temperature sensitivity of the reproduction. Both of these properties contribute to the manifestation of the virulence of the virus. Prolonged circulation of temperature-sensitive viruses can be a prerequisite for the appearance of a radically new drift variant and even shift. Conclusion. The analysis of the variability of the biological properties of influenza viruses approaches to the comprehension of possible ways of their evolution, that contributes to the development of rational methods for preventing the spread of viruses and the incidence caused by them.