orthomyxoviridae

orthomyxo natural resevoir

birds

strains that infect humans

A B C

strains that infect animals

just flu A

orthomyxo genome

enveloped -ssRNA segmented with poly A tail

genome organization

each segment codes for one protein except for M which is alternatively spliced

orthomyxo transmembrane proteins

ha, na, m2

ha

mediates binding

na

involved in egress; prevents progeny from rebinding by cleaving sialic acid receptor

m2

mediated virion escaping the endosome by forming an ion channel with decreased pH

rdrp structure

pb1, pb2, and pa

pb1

catalytic activity

pb2

cap binding

pa

endonuclease that cleaves rna

site of replication

nucleus

cap snatching effects on cellular rna

completely shuts down host translation

cap snatching mechanism

uses free 3’ OH from cellular rna as a primer

ns1

neutralizes the interferon response

blockages caused by ns1

PRRs, PKR/STAT, dsRNA degradation enzyme, nucelar pore so isg and nfkb cannot move into nucleus

amantadine

disables M2 if taken early enough

tamaflu and zanamivir

na inhibitors

potential pandemic of orthomyxo

antigenic shift (more dangerous) and antigenic drift

antigenic shift

acquisition of different genes from other virions from reassortment

antigenic drift

random mutations from the rdrp

flu vaccine

two strains are incubated in a chicken egg; genomes recombine for wide variety of progeny

barriers to reassortment

dual exposure, compatibility of secondary rna structures, need for full genome