Cold/Enterovriuses Flashcards
The Common Cold
Each of these viruses can cause a common cold:
Rhinoviruses - members of the Picornavirus family - the most common cause
Adenoviruses
Enteroviruses (also are Picornaviruses) Coronaviruses
Parainfluenza viruses
These viruses cause acute infection of the upper respiratory tract Nasal mucosa, throat.
Rhinoviruses - grow best at a cool 33°C in upper Res. Tract
Cause release of histamine - symptoms IFN - symptoms Mucous - symptoms
There are lots of serotypes of rhinoviruses
How to Immune System responds to the cold?
Rhinovirus blocks IFN production: less IFN symptoms than flu but is largely controlled by IFN production
Neutralizing antibodies are made weakly, so protection against reinfection is weak.
“hit and run thing”
Why there is no vaccine
Enteric Viruses
Picornaviruses
Enteroviruses - spread via fecal-oral route but replicate mainly in lymph nodes
Poliovirus - spreads to neurons in spine and kills them
HAV - Hepatitis A virus: covered in Hepatitis virus section
(Rhinovirus is a picornavirus but it is is not an enteric virus - it’s a respiratory virus)
Rotavirus
Adenoviruses
Enteric Coronavirus - an enveloped virus there are also non-enteric coronaviruses such as SARS virus and MERS virus
Gastroenteritis viruses characteristics
All are naked viruses (except Coronavirus)
All are icoshedral (except coronavirus which is helical)
All cause gastroenteritis
“Adeno, Rota, Pircornoa, Corona,”
How many kids die each year from Rotavirus?
453,000
Rotavirus
Causes gastroenteritis
Intestinal inflammation, diarrhea, fever, vomiting,
Mostly in children
Can last up to a week
Infect intestinal columnar epithelial cells.
Stool can contain up to a billion virions per mL - even during asymptomatic infection
Virus remains infectious in water.
<10 virions needed to initiate infection (So very virulent)
Babies reliably become infected once maternal antibodies disappear.
Rotavirus structure
dsRNA virus
THREE capsid layers:
1) First capsid layer is removed by intestinal enzymes to make the virus infectious.
2) Transcription happens in virions and ssRNA is squirted out to cytoplasm. During viral assembly, ssRNA is packaged then turned into dsRNA.
This is all designed to hide the dsRNA from the innate immune system to reduce the induction of IFN.
Rotavirus Pathogenesis
Infected cells die, inducing innate immunity anyway but the virus has had a head start by this time and has replicated and now can spread.
Antibodies come up late in infection, and virus is gone by the time they are in full gear.
Antibodies mainly provide (incomplete) protection from reinfection.
Rotavirus Vaccine
Oral, live attenuated vaccines covering multiple serotypes
Causes herd immunity.
Polio
It is a Pircornavirus (fits with some of the enteric viruses)
Spread by fecal-oral route
3 Serotypes of virus - Types 1 - 3
Causes:
Poliomyelitis
Polio
Infantile Paralysis
it is actually a Gastrointestinal Disease that occasionally (very occasionally!!) enters the nervous system, and when it does it can cause crippling effects. And, it can lead to acute flaccid paralysis.
Up to 95% of polio infections are asymptomatic but contagious.
Seasonal, usually peaking in summer
Acute Flaccid Myelitis (AFM)
200 kids have been affected with a polio-like condition & they think they have gotten it narrowed down to an enterovirus - EVD68 isolated from spinal fluid
can lead to sudden arm or leg weakness, drooping eyes, facial droop or difficulty…. – these are all symptoms of a nervous system problem.
