Influenza Virology Overview: Family, Types, Genome, Genetic Change
Influenza, caused by Orthomyxoviruses, comprises Type A, B, and C with distinct subtypes and variants. The genome codes for hemagglutinin and neuraminidase proteins, major antigens responsible for entry and exit from host cells. Genetic changes occur through mutation (antigenic drift) and reassortment (antigenic shift), leading to seasonal and pandemic flu outbreaks.
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Presentation Transcript
Influenza (Family Orthomyxoviruses) Type A Type B Type C Subtypes are serologically distinct. Antibodies do not cross-neutralize between subtypes. ~150 subtypes Variants are somewhere in between. Antibodies generated by one variant will partially neutralize a different variant of the same subtype. Variants or antigenic variants Strains are serologically identical. Antibodies do cross-neutralize between strains. Strains
Influenza A genome Codes for the hemagglutinin protein. Responsible for viral entry into host cells. Most abundant surface protein. Stimulates antibody response. The hemagglutinin is the major antigen of the virus
Influenza A genome Codes for the neuraminidase protein. Responsible for viral budding (exit) from host cells. Second most abundant surface protein. Stimulates a weaker antibody response than HA. The neuraminidase is a target for antivirals.
Mechanisms for genetic change Mutation (Antigenic drift): Point mutations that confer a fitness advantage and spread through the host population Seasonal flu Reassortment (Antigenic shift): The process by which influenza viruses swap gene segments. This genetic exchange is possible due to the segmented nature of the viral genome and occurs when two differing influenza viruses co-infect a cell. Pandemic flu
