Hemagglutinin structure, membrane fusion and virus entry

Influenza A viruses belong to the order Orthomyxoviridae and are responsible for significant annual morbidity and mortality. They are classified serologically based on the antigenic properties of their surface glycoproteins: the hemagglutinin (HA) and the neuraminidase (NA) [1]. To date, 18 HA subtypes, caused by antigenic shift, have been determined [2, 3]. These subtypes can be divided into 6 clades and two groups and this variability makes it difficult to effectively aim any drug against this structure. Furthermore, also antigenic drift can strengthen the ability to escape the virus from effective blockage [4].

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