Antigenic shift

Antigenic shift is a process in virology. Antigenic shift is particularly common in influenza A viruses (see Orthomyxoviridae below) and occurs as a consequence of the segmented nature of their genome when the host cell is simultaneously infected with two subtypes. In turn, genetic reassortment during the replication process can result in new subtypes with mixed gene segments from both "parent" viruses (P-generation). This can affect each of the 8 gene segments alone or in combination with others (see also antigenic drift).

In influenza viruses,antigenic shift mainly affects the genome segments that code for the viral surface proteins haemagglutinin and neuraminidase. In the case of influenza viruses (RNA genome), mutations can occur particularly easily as a result of a special feature of their genome, since it is present in individual sections (segmented). These genome segments can be mutually exchanged when a host cell is simultaneously infected with two different influenza viruses. The resulting reassortant, recombined virus progeny can carry different combinations of (surface) protein molecules due to the altered genome. They thus acquire a new antigenicity. As a result, antigenic shift regularly gives rise to new variants, making it necessary, for example, to readjust a vaccine against seasonal influenza every winter. In the case of influenza viruses, antigenic shift mainly affects the genome segments that code for the viral surface proteins haemagglutinin and neuraminidase.

In Germany, the monitoring of the genetic properties of influenza viruses is primarily carried out at the National Reference Centre for Influenza, which is located at the Robert Koch Institute. The Influenza Working Group provides regular information on this.