Influenzavirus:

http://www.drugdevelopment-technology.com/projects/t705/images/1-influenza-virus.jpg

Influenzavirus:

Properties:

·       Typically Spherical (100nm) diameter)

·       Eveloped

·       Pleomorphic (many forms)

·       Spikes on envelop

·       Groups of HA (hemagglutinin) or NA (neuraminidase)

·       Ratio of HA or NA

·       Single strand (-) RNA in 8 Segments

·       3 polmerase polypeptides with each segment

·       5’ and 3’ end of all segments highly conserved

Pathogenesis:

·       Respiratory tract in human

·       Affinity of the HA for receptors in the epithelium of the tract.

·       Innate resistance

·       Mucus blanket/cilia

·       Immunocompromised

·       Elderly

·       Premimies.

Epidemiology:

·       all throughout the year

·       incubation (1 to 4 days)

·       a few serotypes circulating simultaneously

·       virus abundant in nasal discharge

 

Antigen Drift/Shift

·       Antigenic drift is a mutation in the genetic code of surface antigens (HA/NA) (type A* and B*)

·       Antigenic shift occurs when genes re-assort from different subtypes (only types A*) (once 10-40 years)

 

Antigenic Drift	Antigenic Shift
Minor change in genome	Major change in genome
Both in A* and B*	Only in A*
Point mutation	Gene reassortment
Result in new strain	Result in new subtype
Happens at all time	Happen occassionally

*A mean influenza A

*B mean influenza B

 

Control:

·         Vaccine for influenza (rendered useless by Antigenic shift/ drift)

·         Antiviral drugs

Ø  Receptor analog (prevent attachment)

Ø  Transcriptase inhibitors

Ø  RT inhibitors

Ø  Protease inhibitors (post-translational cleavage)

Ø  Assembly of virions