13 GI tract2 Flashcards
is picornaviridae enveloped
no
what is the capsid of picornaviridae like
icosahedral
what are the fold axis of symmetry in picornaviridae
2 fold
3 fold
5 fold
what is pico
small
what surrounds the genome in picornaviridae
spherical, non-enveloped capsid
what class virus is picornaviridae
IV
what RNA is picornaviridae
+ssRNA
what can the picornaviridae RNA do
directly translate as +RNA
what is picornaviridae like
- large ORF
- covalently linked protein VPg
- non-segmented
what is the baltimore classification of picornaviridae
IV: +ssRNA
what does poliovirus cause
paralysis
aseptic meningitis
what is enterovirus route of transmisson
faecal-oral
what are the stages of enterovirus life cycle
- attachement/penetration
- penetration
- primary translation
- replication (-) and (+) strand
- secondary translation
- assembly
- virion exit by cell lysis
what happens in stage 1 of enterovirus life cycle
- virus binds to receptor on cell
> ejection of VP4 = viral capsid structural changes
what happens in stage 2 of enterovirus life cycle
- uncoating of vRNA = enters cytosol
what happens in stage 3 of enterovirus life cycle
viral RNA translates proteins of poliovirus
non-capped mRNA
polyribosomes translate polyprotein, using cap-independent translation
what is the effect of the stages in stage 3 of primary translation
cellular translation is blocked = translational control
lytic or fast growing viruses
what happens in stage 4 of enterovirus life cycle
(+) replciation just made (-) sense strand then serves as template for more (-) strands RNA (+ mRNA)
what happens in stage 5 of enterovirus life cycle
mRNA strands serve as templates for more translation of polyprotein
some RNA packaged
what happens in stage 6 of enterovirus life cycle
P1 cleaved to make VP0, VP3, VP1
If more infectious cleaves VP0 into = VP2 and VP4
RNA must be inserted in virion = packaging
what happens in lysis of enterovirus life cycle
~10^5 virions per infected cell released during cell lysis
what are the outcomes of poliovirus exposure
paralytic poliomyelitis
non-paralytic poliomyelitis
abortive or minor illness
unapparent infection
what is the % of paralytic poliomyeltitis
0.1-2%
what is the % of non-paralytic poliomyelitis
0.1-2%
what is the % of abortive or minor illness
4-8%
what is the % of unapparent infection
95%
what does bulbar polio cause
motor neurons of brain affected
reduced breathing, difficult to speak and swallow
what is used to aid bulbar polio
iron lung to aid breathing
is enterovirus - poliovirus common
rare due to infant immunity
what are the symptoms of poliovirus
fever fatigue headache vomiting sore neck some get paralytic poliovirus
what has reduced passive immunity in poliovirus
due to plumbing - sanitation
what leads to increase in polio cases
aetiology still unknown
how is Salk PV vaccine inactivated
formaldehyde
heat
pH
how many serotypes of salk PV vaccine are there
3 serotypes
where and how is PV grown
in the lab
using tissue culture
what is Salk PV also known as
IPV
what is the oral enterovirus vaccine for poliovirus known as
sabin
what is the sabin vaccine like
attenuated
what is VAPP
vaccine associated paralytic poliovirus
how effect is sabin
100% efficacy after three doses
what is the affect of VAPP
as attenuated is live and can replicate in the gut
what causes the attenuated mutation in poliovirus vaccine
in 5’ NCR (non-coding region) of PV
RNA secondary structure of the poliovirus 5’ non-coding region
VAPP/Attenuating mutations of PV 1-3
Mutations in domain V
U would have to revert back to C to get a wildtype
Exposed to wildtype poliovirus= infected
what is the inactivated polio virus vaccine
Salk
what are the advantages of inactivated dead poliovirus vaccine
- Safe
- Can be used for immune-deficient (or suppressed) patients
- High uptake
- Excellent systemic immunity
- No reversion, no excretion of wild-type into community
what are the disadvantages in poliovirus inactivated vaccine
- Requires repeated IM injection and is more expensive
- Limited mucosal/intestinal immunity compared to live
- risk due to use of wt virus as seed for vaccine
what are the attenuated poliovirus vaccine advantages
- Strong systemic and intestinal immunity (cannot pass through as easily)
- Inexpensive
- Oral delivery
- Relatively safe
- Herd immunity: virus is excreted into the environment
what are the attenuated poliovirus vaccine disadvantages
- Can mutate to NV form (neurovirulent form) – causing VAPP
- Requires monkeys for testing
- Unsuitable for immunodeficient and immunosuppressed individuals (as live)
- Can lead to Vaccine Derived PV leading to outbreaks cVDPV (circulating VDPV)
why should eradication of poliovirus feasible
- no animal reservoirs
- virus is not airborne
- only three serotypes
- Poliovirus entry into cells is very inefficient
how can we eliminate poliovirus
stop using the attenuated vaccine
to stop VAPP
