Flashcards in Micro 2 Deck (209)
What is orthoreovirus?
A member of reoviridae
Infects mammals, but not associated with serious disease in humans.
What kind of virus is rotavirus?
-dsRNA genome - 11 segments
-most important cause of gastroenteritis in young children
-group A assoc. w/ human disease
What cells do Rotavirus infect?
How long is incubation?
Tip of villi in sm. intestine
- as few as 10 particles can cause infection
-1-4 days incubation period
Describe rotavirus pathogenesis
virus capsid proteins attach to glycolipid receptor on the apical enterocytes of sm. intestine villi.
-Damage to sodium and glucose absorptive mechanisms -> increased luminal H2O volume. Viral replication -> acute onset of vomiting and diarrhea
-Activation of intestinal nerves -> secretion of H2O
-Fluid accumulation in lumen of sm. intestine, 10-20 diarrheal episodes / day and severe dehydration
Describe rotavirus structure
Unenveloped, icosahedral, 3 layer protein capsid
Segmented dsRNA genome
capsid contains all enzymes needed for replication
VP4 receptor protein - binds glycolipid of host cell
What are the major coat proteins of rotavirus?
VP4 - outer coat - binds receptor (sialic acid / integrins)
VP7 - outer coat - stripped during endocytosis
VP6 - middle coat - major protein that is tested for in antibody titer
VP2 - inner coat
How is rotavirus infection diagnosed in a lab setting?
Presence of virus particles in feces early in illness
- immune electron micoscopy, ELISA, immunoassay
Rise in titer of Ab to VP6
What are the two most important viruses contributing to diarrheal illness in children?
What type of genetic material is carried by Adenovirus?
What is the most common cause of viral gastroenteritis in older children and adults?
How is norovirus transmitted?
also contaminated food: shellfish and contaminated water
How long is the Norovirus incubation period and how long does it remain contagious?
incubation: 12-48 hours
From onset of symptoms: highly contagious until at least 3 days after symptoms recede - infectious viral particles may be shed as long as 2 weeks after illness
Acute onset of vomiting, diarrhea, stomach cramps, headache, fever, chills, myalgia
symptoms resolve 24-48 hours after onset.
How is norovirus spread prevented?
Handwashing - soap and water (alcohol hand-gel is inadequate)
10% bleach to clean surfaces.
What family of viruses is norovirus from?
What is norovirus genome?
What virus families do Hepatitis viruses A-E belong to?
Hep A: Picornavirus
Hep B: Hepadnavirus
Hep C: Flavivirus
Hep D: satellite virus - undefined classification
Hep E: Hepevirus (Hep - E - virus)
Genomes of Hepatitis A-E
D: ssRNA (-)
Which Hepatitis viruses produce chronic illness?
B and C
D in the context of association with B (is not infective on its own)
What causes hepatic cellular carcinoma
Chronic viral infection is leading cause (HBV, HCV)
course of chronic illness is 25-50 years
Ultimate cause: constant inflammation and constant stimulation of cellular replacement -> mutation and tumor formation
What was the first successful recombinant vaccine for a human disease?
Hep B vaccine
How is HBV spread?
sexual contact and parenteral exposure
most adults clear infection - 5% do not -> chronic infection
--May be asymptomatic
Describe the HBV genome
Circular, partially double stranded DNA.
Full length (-), 20-80% (+)
Describe the process of HBV replication
Genome is circular (-) DNA with partial (+) DNA. In nucleus, cellular DNApol -> full dsDNA
(-) DNA -> full length (+) RNA via host cell RNA pol II
(+) RNA is packaged in new core proteins
viral RNA/DNA dependent DNApol -> full length (-)DNA
(-)DNA copied by viral DNApol -> partial (+) DNA
HBsAg containing envelope acquired on exocytosis
How is HBV prevented / treated?
Interferon - alpha and/or inhibitors of HBV polymerase
**These do not eliminate infection***
Describe Hep D'd genome and what it codes
Small (-)RNA genome (1.7kb)
codes one protein: delta antigen: RNA encapsidation
What is HDV superinfection?
Infection w/ HDV after host is already infected with HBV.
contrast w/ coinfection, where both acquired together
Superinfection -> high mortality (20%)
What family of viruses does HCV belong to?
Describe HCVs genome
(+)ss linear RNA