Antigen shift
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Antigen shift describes the exchange of genetic information between different virus types or subtypes. For this purpose, the viruses must have a segmented genome so that individual segments can be exchanged between the viruses within the same cell during reproduction; the genetic process itself is called reassortment or reassortment .
The term antigen shift is particularly known from influenza viruses , since an antigen shift leads to the appearance of new pathogenic variants and is responsible for the outbreak of global pandemics . In contrast to the antigen drift , an entire gene segment is exchanged here. This creates new subtypes with new combinations of surface antigens (for example hemagglutinin and neuraminidase in influenza A / H5N1 ). The condition for an antigen shift is the simultaneous infection of a host cell (for example in the common host pig or duck ) by different virus strains. It is assumed that the antigen shift is based on a targeted viral mechanism, i.e. that the antigen shift does not happen by chance.