Flu Virus All RNA viruses Key pieces o Envelope outer covering containing the capsid Covered with protein spikes antigens 2 kinds 1 H antigen hemaglutin o Responsible for host recognition o Looking for particular receptor on host cell surface o Bonds with receptor which lets the virus into the cell o Once in the cell the virus hijacks cellular replication synthesis machinery to build new virions o Once built the 2nd protein spike becomes important 2 N antigen neuraminidase o Responsible for getting virions out of cell without killing the cell no cell death lysis We use H and N antigen subtypes to classify flu viruses o 15 H subtypes o 9 n subtypes Lots of potential viral diversity o Likely the result of high mutation rates in RNA viruses o Problematic for vaccine design o Fighting a moving target o Each new H and N grouping requires a new vaccine o Also effected by H and N arrangement on envelope o Also problematic for human immune system Antibodies Fights viruses and diseases Specific to a given flu Result of exposure to particular viruses infections Possess them for life o Why are RNA viruses including flu prone to mutation Increased mutation rates during RNA replication due to high error rate of this process more error than found with DNA replication DNA has error checking mechanism which RNA lacks RNA errors 1 Leads to viral breakdown 2 Changes how it impacts affects host 3 Change mode of spread of virus 4 Changes how infectious it is Antigenic Drift direct mutation with antigens Antigenic Shift new viral strains that result from mixing of existing strains 5 Can change antigens H N Attack unvarying stable but still functionally important structure on virus Universal Flu Vaccine o Not target antigens o Target envelope or capsid Avian Flu H5N1 High mortality spreads easily Reservoir Species where virus starts o Wild bird population where flu cycled first o Some mutation even RNA happened and caused a host jump o Now cycles in domestic birds chickens turkeys causing high mortality rates o Another mutation another host jump now to humans No cycling among humans Just from birds to humans Swine Flu H1N1 General cycle 1 Attaches 2 Taken into vesicle 3 Vesicle breaks down and viral RNA comes out 4 RNA goes to nucleus 5 Replicates 6 Builds new pieces and parts outside nucleus
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