Lec 9 - Acute Viral infections 2 Flashcards
what is structural plasticity
to what extent virions can tolerate amino acid substitutions and remain infectious
antigenic drift
modification of amino acid sequence which change the antigenicity of the virus by error prone replication of genomes especially in RNA viruses
antigenic shift
major change in surface protein of a virion f=after acquistion of new genes
due to genome reassortment during genome packaging
which one causes pandemics
antigenic shift
influenza viral charceristics
-ve ssRNA virus with 8 segments
influenza types, and which ones are important
A B and C
A and B cause disease
infleunza A
in birds and mammals
can go thorugh shift and drift
(cause of pandemics)
influenza B
in humans only
which sialic acid can human flu HA adhere to
alpha 2,6 linked sialic acid in upper resp tract
which sialic acid can avian HA adhere to
alpha 2,4 sialic acid in lower resp tract
complications of influenza
- primary viral pneumonia
- seondary bacterial pneumonia
- muscle pain
- cardiac complications
- reye syndrome
what can reye syndrome cause
in kids mostly
encephalopathy
liver function problmes
what does HA do
promote adhesion to sialic acid on epithelial cells
and
promote fusion of viral and endosomal membranes to promote delivery of ribonucleocapsid
what does NA do
hydrolysis of terminal sialic residues from new virions and host cell receptors to allow exocytosis
In serotype A, how many HA and NA subtypes are there
18 HA
11 NA
what are the 3 combinations of serotype A in humans
H1N1
H2N2
H3N2
what are the 2 major lineages of serotype N
Victoria and Yamagata
only slight differences
what are lineages of B based on
the antigenic properties of HA
why only 1 serotype for influenza B
no animal resevoir
mutation rate is 2-3x slower
why tamiflu and relenza not great
high resistance
which virus causes severe diarrhoea
rotaviruses
how is rotavirus similar to flu
segmented RNA genome means a cell can be co infected by 2 viruses and genome reassortment can occurt
how come rotavirus is so robust
3 concentric layers:
inner
intermediate
and external
which proteins on rotavirus are antibodies targeted to
VP7
