Abstract

Influenza viruses of the family of Orthomyxoviridae cause annual epidemics in humans, and are frequently found in birds and various mammalian species. Influenza A viruses can be divided into subtypes as determined by the viral surface glycoporteins hemagglutinin (HA) and neuraminidase (NA). The HA protein is the main target for neutralizing antibodies against influenza A virus. However, antigenic variation of HA, which is referred to as antigenic drift, results in immune escape that facilitates the recurrence of seasonal epidemics and multiple infections during one’s lifetime. In order to understand what determines influenza A virus evolution rate and direction it is necessary to measure the fitness of the virus. Viral growth is one of the key parameters studied in influenza virus research as a proximity marker for virus fitness. Therefore, we require experimental techniques to determine influenza virus replication with extreme precision. We have previously shown that multistep replication kinetics are not sensitive enough to distinguish small replication differences between two different influenza A viruses and that measuring plaque sizes of viruses is a preferred method to read out viral growth. We are applying this technique to study the fundamental dynamics of the evolution of influenza viruses.