Viral Gastroenteritis Flashcards
1
Q
Viruses that can cause gastroenteritis
A
- Norovirus (Calciviridae)
- Single RNA (+) sense
- Rotavirus (Reoviridae)
- Double shell, 11 genome fragments of dsRNA each encode single protein
- Astrovirus
- Non-enveloped ss(+)RNA virus
- Enteric adenovirus
- Icosahedral DNA virus
- Picobirnaviruses
- Icosahedral DNA virus
- Bocavirus
- Icosahedral DNA virus
- Coronavirus
- (+) strand RNA genome
2
Q
Norovirus: details and serotypes
A
- Single RNA (+) sense
- Foods, water, shellfish
- 50% attack rate 2 days; need only 10 to get it
- Genogroups: GI, GII, GIV
- Most common cause of gastroenteritis
- Serotypes:
- Norwalk
- Hawaii
- Montgomery
- County
- Cockle agent
- Snow Mountain agent
- Marin County agent
3
Q
Rotavirus: details and serotypes
A
- Double shell, 11 genome fragments of dsRNA each encode single protein
- Vaccine –> decreased incidence
- 2 capsids:
- Outer = VP7
- Spike protein = VP4
- NSP4 = enterotoxin; non-structural protein
- 3rd most common cause of gastroenteritis
- Require trypsin activation for virulence
- Serotypes 1-4 of 9 total
4
Q
Astrovirus: details and serotypes
A
- Non-enveloped ss (+) RNA virus
- 2nd most common cause of gastroenteritis
- Can cause viremia - newer discovery
- 7 serotypes identified
5
Q
Diagnosis of gastroenteritis viruses
A
- Most viruses can’t be isolated in cell cultures
- History –> virus more likely to cause vomiting
- Also has rapid onset, shorter duration compared to bacterial
- Use data –> viral antigen detection arrays + PCR
- Newer tools used for identification, only recently available
- Norovirus: ELISAs and RIAs to detect norovirus antigens in stool
- RT-PCR more sensitive, used to differentiate strains by RT-PCR of less conserved genes (e.g. capsid)
- Rotavirus: ELISA or rotazyme test
- RT-PCR can identify virus antigens or RNA in stools quickly
6
Q
Rotaviruses: replication and pathogenesis
A
- Double shelled with 11 genome segments of dsRNA
- Contains dsRNA-dependent RNA polymerase and other enzymes
- Each genome segment encodes ss-mRNA which makes one protein
- Reassortment of genome segments occurs whenever two different rotaviruses infect the same cell
- Rotavirus virions assemble at RER –> inner cores are enveloped in transient envelope –> loses lipid –> becomes outer protein shell of virion in lumen of RE
- Virions NOT infectious unless activated by treatment with trypsin
- Trypsin available naturally in gut
- Trypsin cleaves outer capsid protein & aids in virus uncoating
- NSP4 (viral non-structural protein) = secreted enterotoxin that increases intracellular Ca2+ levels in infected cells –> alters signal transduction –> alters ion transport in intestinal epithelial cells –> diarrhea
7
Q
Norovirus: replication
A
- Genomes are 7.7kb, ssRNA (+) messenger sense
- Genome includes:
- ORF1 at 5’ end
- Encodes RNA-dependent RNA polymerase and structural proteins
- ORF2
- Encodes capsid and major viral capsid protein VP1
- ORF3 at 3’ end
- Encodes minor, highly variable structural protein VP2
- ORF1 at 5’ end
- Cleavage of viral polyproteins by virus-encoded protease required for virus replication
- Virus-encoded protease is potential drug target
8
Q
Most likely virus causing epidemic in nursery
A
Rotavirus
9
Q
Most likely virus causing epidemic in daycare
A
Astrovirus - identified in 34% of daycare center outbreaks
Rotavirus
10
Q
Most likely virus causing epidemic in school
A
Astrovirus, Norovirus
11
Q
Most likely virus causing epidemic in nursing home
A
Astrovirus, Norovirus
12
Q
Most likely virus causing epidemic in contaminated shellfish
A
Norovirus
13
Q
Most likely virus causing epidemic in water
A
Norovirus
14
Q
Type of immunity most likely to prevent viral gastroenteritis
A
- Humoral immunity
- Only lasts for a few months
- Different serotypes prevent cross-immunity
15
Q
Vaccines for norovirus
A
- Would need several serotypes
- Plants have norovirus protein & recombinant ones that are vaccine candidates
- Insect cells can also assemble capsids
