Lec 27 Enteroviruses Flashcards
What are picomaviruses? What are the 3 types of picomavirus?
picomavirus = small RNA virus
enteroviruses
rhinoviruses
hepatitis A
What are the common types of enterovirus?
- poliovirus 1-3
- coxsackie A and B
- echoviruses
- numbered enteroviruses
When do enterovirus infections occur and where?
in temperate climates: summer and fall
in tropics: year round
Who gets enteroviruses?
most cases in children
What are symptoms of enterovirus?
- most are asymptomatic or cause non-specific fever with mild resp symptoms
What are the viral characteristics of enterovirus?
- pos sense
- single strand
- RNA
- icosahedral capsid
- no envelop
- resistnat to harsh environmental conditions –> survives in sewage, broad pH range, GI, detergents
What is aseptic meningitis?
have symptoms and WBCs on spinal tap but using convential bacterial media, nothing grows
means the meningitis is due to something else [like a virus!]
What is role of canyon in center of enteroviruses?
- contains VP1 capsid protein receptor binding sites –> means RBS is hidden from antibodies
- VP1 RBS is responsible for adherence to host cell receptors
Can viruses with or without envelope survive in environment longer / harsher?
no envelope
How are enteroviruses transmitted?
- enter through GI tract via fecal-oral route
- except rhinovirus which is via nasal secretions
What is the pathogenesis of enterovirus and what is replication cycle like?
- enters GI and causes infection there, if pt does not have secretory IgA to virus –> get primary viremia in blood stream –> goes to target tissues
- receptor it binds to [and thus type of cell it invades] depends on type of virus, binds via VP1
- replication occurs in cytoplasm [no nuclear]
- usually cytolytic = ends up killing cell as it leaves [except hep A which is more immune mediated]
- inhibit host cell RNA synthesis
What is pathogenesis of polio?
- travels via nerves from muscle to motor neurons in anterior horn and brainstem
- get meningitis, encephalitis, paralytic disease
What is pathogenesis of HAV?
- travels to liver and get hepatitis
What is pathogenesis of coxsackle?
- goes to brain and get encephalitis
- cox A/B go to muscle and get myocarditis, pericarditis, pleurodynia
- cox A goes to skin and get hand food and mouth, rash, herpangina
What is pathogenesis of Echo?
- myocarditis
- in neonatal –> myocarditis, liver failure, death
- also meningitis/cold/fever/rash in summer
What are possible target tissues of enteroviruses?
- skin infections
- muscle –> heart
- brain
- meninges
- liver
- can cross placenta and infect fetus
For how long are enteroviruses still contagious in pt infected?
may have symptoms for a few days but still shed virus in nasal secretions and stool for weeks
What are the mech of enterovirus injury?
cytolytic except in hep A
immune mediated in hep A
What are the roles of secretory IgA and serum IgG in enterovirus immune response?
sec IgA: prevents establishment of initial infection
serum igG: prevent/control viremia
What are the symptoms of polio?
90% asymptomatic
5% minor febrile illness
non-paralytic aseptic meningitis 1-2%
paralytic 2% –> get asymmetirc flaccid paralysis
What are the two polio vaccinces?
inactivated [IPV]: IM, get serum IgG antibodies, does not cause disease
live [OPV]: oral, get both secretory IgA antibodies and serum IgG, cell mediated + long lasting, possibility of getting sick
Which polio vaccine do we get?
- in places where we don’t really have polio we use inactivated
- use activated in places where polio is still common
Where is polio endemic?
afghanistan
nigeria
pakistan
What are clinical syndromes associated with enteroviruses other than polio?
- exanthems [widespread rash
- febrile illness
- URI
- acute hemorrhagic conjunctivitis
- aseptic meningitis and encephalitis
= fever + rash often is enterovirus
