RNA Virus 1 Flashcards
RNA Viruses:
replicate in…
ds or ss?
special machinery requirements?
Replicate in cytoplasm (except influenza and retrovirus)
most ss RNA
(+) can be read like mRNA. Genome encodes for RNA-depedent RNAPolymerase
(-) require synthesis to (+) before viral proteins can be made… Virus particle contains RdRNAp
Naked viruses
Pico *
Calici *
Astro *
Reo *
Enveloped virus
Toga * Flavi * Bunya Arena Rhabdo Paramyxo Corona Filo Retro
Enterovirus disease
- Vesicular disease / aseptic meningitis
- gastrointestinal disease
- respiratory disease
Arbovirus diseases
encephalitis and hemorrhagic fever
spread by arthropods
PicoRNAvirus:
types
Enterovirus
Hepatovirus
Rhinovirus
Picornavirus: genome (ss/ds, +/-)... envelope? capsid... attachment... replication... release...
- Single strand
- Positive sense
- Naked (no envelope)
- Icosahedral capsid of 60x non-glycosylated proteins
- attach/entry via receptor-mediated endocytosis
- replicate in cytoplasm
- release by lysis
Picorna attachment
cell receptors part of IG superfamily (binds to canyon region on vertices of virus)
receptor for Polio attachment
PVR/CD155
receptor for rhinovirus and several coxsackievirus
ICAM-1
Picornavirus replication scheme
One polyprotein is translated and then cleaved by viral protease.
Picornavirus transmission
Transmitted via fecal-oral and respiratory secretions
Picornavirus disease
Enterovirus (10-15mil/yr)
Rhinovirus (mils/yr) — most common cause of common cold
Rhinovirus pH/temp optimums
acid labile (neutral better) Topt = 33*C (cooler in the nose)
Enteroviruses / HepA
pH/temp optimums
Acid resistant (pH 3-9) also resistant to detergents, heat, mild sewage treatment
Where do enteroviruses replicate?
mucosa and lymphoid tissues GI tract… causes viremia
Enterovirus primary and secondary viremia patterns
1* viremia spreads virus to target tissues
2nd phase of viral replication occurs at targets, resulting in 2* viremia and SYMPTOMS
Poliovirus infections symptoms
-where does it infect?
- mostly asymptomatic
- symptoms range from mild fever / diarrhea to flaccid paralysis
- 2% aseptic meningitis
- 1% permanent paralysis
- infects:
ant. horn cells of spine
motor cortex of brain
Poliovirus vaccination
-three serotypes covered
- Inactivated Polio Vaccine (IPV) - killed
- Oral Polio Vaccine (OPV) - live attenuated
-only IPV used in US since 2000
Coxsackie A virus diseases
aseptic meningitis
herpangina
hand, foot and mouth disease
conjunctivitis
Coxsackie B virus diseases
aseptic meningitis
myocardial and pericardial infections
pleurodynia
Echovirus diseases
aseptic meningitis (outbreaks every summer)
Parechovirus diseases
respiratory
gastrointestinal
encephalitis (rare)
myocarditis (rare)
Kobuvirus disease
gastrointestinal
What characterizes enterovirus vesicular disease?
Hand foot and mouth disease (papular skin rash)
Herpangina (blister-like sores in mouth)
What are most common causes of vesicular disease
Coxsackie A16
Enterovirus
treatment for enterovirus vesicular disease
only symptom relief
diagnose enterovirus vesicular disease
typically clinical
when is enterovirus meningitis most common
summer / early fall
most common / other causes of viral meningitis
** Enterovirus Mumps Herpesviruses (EBV, HSV, VSZ) Measles Influenza Arbovirus LCMV
Symptoms of viral meningitis in infants and young adults
fever
irritability
poor eating
hard to awaken
Symptoms of viral meningitis in adults
high fever severe headache stiff neck sensitivity to bright light sleepiness / trouble rousing nausea vomiting lack of appetite
viral meningitis time course and recovery
usually last for 7-10 days - recover normally
treatment for viral meningitis
nothing specific… supportive care
diagnosis for viral meningitis
detection of virus particles
serology (retrospective)
What about Entervirus 68?
disease…
virus particles found…
transmitted…
Entervirus respiratory disease… symptoms with wide range of severity
virus found in respiratory secretions (saliva, mucus, sputum)
spread by sneezing / coughing, and fomites
Other manifestations of enterovirus
besides respiratory / meningitis / vesicular
viral conjunctivitis (cox A, entero 70) myocarditis pericarditis encephalitis paralysis
Diagnose Enterviruses
methods
PCR (RT-PCR) for virus in tissues
Virus isolation / culture
Serology (acute & convalescent) is helpful
Diagnose Enteroviruses
limitations
sensitivity…
viremia undetectable at time of symptoms (viremia occurs first)
CSF specimen during acute phase are sometimes negative
Treatment for enterovirus
supportive care
Principle agent of common cold
Rhinovirus
Rhinovirus binds to ____ on cell surface
ICAM-1
Where does Rhinovirus infect?
upper respiratory tract
Why is reinfection with rhinovirus so common
IgA immunity is short-lived
More than 100 independent serotypes of Rhinovirus
Rhinovirus incubation period and acute symptom timeline
1-2 days of incubation
3-7 days of acute symptoms
Treatment for Rhinovirus
nothing specific
no good vaccine
*possible block of receptor attachment
HAV: Transmission: 1* Replication site: Virus particles excreted (when): Spreads to:
Hepatitis A Virus
Fecal-Oral transmission
Initial replication in enteric mucosa
Virus excreted in feces BEFORE symptoms
Spreads to liver w/ 2* viremia
HAV incubation
15-45 days
“short incubation”
HAV Early Symptoms (Prodrome)
fever nausea anorexia abdominal pain (RUQ) dark urine clay-colored stool
HAV
Icteric phase symptoms
jaundice
pruritis (itching)
enlarged / tender liver (3-4 weeks)
HAV
Fulminant infection
Rare
develop rapidly
lead to severe / life-threatening liver failure
Diagnose HAV
- clinical
- lab
Clinically
- elevated ALT
- jaundiced
Lab
- positive IgM anti-HAV
Is HAV commonly cause a chronic or acute disease?
acute common… lasting 3-6 months
Other causes of viral hepatitis (besides HAV)
CMV
EBV
Coxsackie virus
Other causes of hepatitis (besides viral)
Toxoplasmosis (and other inf) Drugs, alcohol Cholescystitis Pancreatitis Autoimmune disease
HAV vaccination is recommended for:
- international travelers
- Men having sex with men
- drug users
HAV vaccination form (inactive, dead, etc)
- inactivated whole virus
- it’s a cell culture adapted, inactivated with formalin
What is twinrix?
The HAV and HBV mixed vaccine
When should HAV-Ig be administered to patient living with someone who’s Hep-A infected
within 2 weeks of last exposure
80-90% effective at preventing clinical Hep-A
RNA viruses that cause gastroenteritis
calicivirus
astrovirus
rotavirus (reovirus family)
Two main factors contributing to wide-spread transmission of viruses causing gastroenteritis
- large quantities of virus are shed in the stool
- virus is resistant to the environment
Calicivirus:
genome (ss/ds, +/-)…
envelope?
capsid…
- positive sense, single strand genome
- naked
- single icosahedral capsid
Norovirus is the primary agent responsible for ____
most acute diarrheal disease
- cruise ships
- day care centers
(90% of all viral gastroenteritis)
Norovirus named from
Norwalk strain (Norwalk, ohio)
How many genogroups?
five (G-I to G-V)
GII.4 is predominant
Norovirus transmission
Fecal-oral
contaminated food
fomites
aerosol (vomiting)
How are virus particles spread?
high levels shed in diarrhea and vomitus
Norovirus only requires ____ for infection
10 virus particles
Norovirus incubation time
24-48 hours
Norovirus pathogenesis
- GI infection leads:
- maldigestion / accumulation of carbs
- malabsorption of nutrients
- inhibition of water absorption
- mucosa remains intact
Treat Norovirus
supportive care
- recovery usually complete
Diagnose Norovirus
- RT-PCR
- sequencing for genotype determination
- rapid enzyme immunoassay - poor sensitivity
- cannot be grown in cluture
Astrovirus
genome (ss/ds, +/-)…
envelope?
capsid…
- positive sense, single strand genome
- naked
- single icosahedral capsid
What does astrovirus look like on TEM
star-shaped
Astrovirus is associated with _____, particularly in children
mild gastroenteritis outbreaks
Astrovirus in acid / heat…
Acid-stable
Heat-resistant
How is astrovirus cultured?
It’s cannot be cultured, dummy!
Reovirus
important types
Rotavirus
Colorado Tick Fever
Reovirus: genome (ss/ds, +/-, circular/segmented)... envelope? capsid... nucleocapsid...
- segmented, double-strand RNA genome
- icosahedral capsid
- naked
- nucleocapsid has three concentric shells, surrounding 11 segments of ds RNA
What is the leading cause of severe acute gastroenteritis among children worldwide
Rotavirus
What are the main antigenic determinants of Rotavirus
VP7 and VP4
What is the name of the protease-cleaved protein on the rotavirus capsid?
VP4 (P protein)
What is the name of the glycoprotein on the rotavirus capsid?
VP7 (G protein)
how many serotypes are there for rotavirus?
5 strains (G1-G4, G9), based on capsid antigens
How is rotavirus transmitted?
Fecal-oral route
Highly contagious
Is the rotavirus particle stable?
You better believe it
When do rotavirus infections typically occur in the US
Late fall - early spring
Rotavirus:
replication site
incubation
- replicates in villous epithelium of small intestine
- incubation 1-3 days, followed by abrupt disease onset
Describe Rotavirus infection.
It’s localized, causing decreased intestinal absorption of glucose, water and sodium.
What are the symptoms of Rotavirus?
- Vomiting
- abdominal cramps
- low-grade fever
- frequent, copious, watery stools
Treat Rotavirus
supportive
rehydration, electrolytes
Most severe cases of Rotavirus occur in which population?
infants and children
severe diarrhea
Diagnose Rotavirus
detection of viral particles and antigens in stool.
Rapid antigen detection test
What are the two rotavirus vaccines?
Method of delivery?
Live/dead?
Only for whom?
RotaTeq and Rotarix
Oral administration
Live virus
only for Infants
RotaTeq…
[RV5]
pentavalent human-bovine Reassortment Rotavirus Vaccine
Rotarix
[RV1] Monovalet Human Rotavirus Vaccine
Rotavirus hazard
Intussusception — bowel blockage from folding back onto itself.
Colorado Tick Fever disease characterized by
acute disease with fever, headache, sever myalgia
Colorado Tick Fever is caused by what agent?
Reovirus
Describe the Reovirus genome
12 ds RNA segments
Hepatitis E virus genome (ss/ds, +/-)... envelope? capsid... incubation... mode of transmission...
- positive sense, single strand RNA
- naked
- icosahedral capsid
- avg 40 days / range 15-60 days
- Fecal-Oral transmission
What is the natural host of HEV?
Humans
What’s the major cause of acute hepatitis worldwide?
HEV
Incidence of HEV in the US? (high or low)
Low
How does HEV disease present?
frequently subclinical…
acute disease may fulminate…
15-25% in pregnant women.
In which groups is HEV common?
common in adolescents and pregnant women.
How does HEV present in children?
children usually have mild or no symptoms
HEV risk factors
Poor sanitation (fecal-oral)
HEV prevention
drink clean water
Treat HEV
hydrate or die
Diagnose HEV
IgG detection (not routine)