Viruses of Gastrointestinal Illness Flashcards
Rotavirus
Most common viral cause of severe diarrhea in young children. Almost all children are infected by the age of 3-5 years.
Clinical Manifestations of Rotavirus
Infants/young children (6-24 mo), can be anywhere from asymptomatic to severe dehydrating gastroenteritis with fever, vomiting, and WD.
Transmission of rotavirus
Mostly fecal-oral and can include fomites because the virus is resistant to desiccation. Large number of rotavirus particles shed prior to, during, and even after illness. Some evidence of respiratory spread
Incubation time of rotavirus
<48hours
Diagnosis of rotavirus?
Elisa or latex agglutination to detect viral antigen in stool samples, RT PCR, isolation in cell culture is possible
Classification of Rotavirus
Genus in the family Reoviridae
How many serogroups of rotavirus
7 A-G
A, B, and C found in both animals and humans
D-G found only in animals.
Serotypes within serogroups
VP6
Rotavirus serogroup determined by reactivity of antibodies with VP6 on ELISA
Which serotypes most important for human disease?
Group A G1, G2, G3 and G4
How to determine seroTYPE
Based on reactivity of antibodies with VP7 or VP4 (P antigen).
Function of NSP4
ER protein/assembly enterotoxin, plays an important role is diarrhea
Rotavirus structure
Wheel like shape, non enveloped virus with 3 layer (double layered capsid and core) protein structure. Segmented double stranded RNA.
3 layer structure component proteins
VP4 and VP7 are outer capsid proteins
VP6 is inner capsid protein
VP2 is core protein
Where does rotavirus replicate?
In the cytoplasm of the cell
P antigen
VP4
G antigen
VP7
Rotavirus replication cycle
Replication within cytoplasm, only viral enzymes used, dsRNA always is associated with subviral particles, subviral particles form and mature by budding through the ER where outer capsid proteins are acquired.
How does RNA synthesis by dsRNA viruses work?
Full length + sense RNAs are created to make protein and contribute to replication
pathogenesis of rotavirus
Diarrhea begins before significant damage to the intestinal mucosa occurs, this is what distinguishes rotavirus diarrhea from bacterial diarrhea. Also, viremia occurs. PIP3 mediated release of calcium which causes secretory diarrhea.
Immunity to rotavirus
First infection induces homotypic immunity against VP7 and VP4, subsequent infections induce more cross protective immunity. Antibodies in the lumen of small intestine are most important for protection, but T cells are also important.
RotaTeq
A live pentavalent human-bovine rotavirus reassortant vaccine, licensed for infants younger than 32 weeks, given in 3 oral doses.
Rotarix
Monovalent rotavirus vaccine derived from most common human rotavirus strain, attenuated by serial passage.
Intussuseption
When a part of the intestine invaginates into a neighboring section, a complication of a certain rotavirus vaccine that was discontinued.
Norovirus clinical manifestations
Acute gastroenteritis, most common cause of nonbacterial gastroenteritis outbreaks. Fevers, vomiting, watery diarrhea, constitutional symptoms. Adults tend to have diarrhea, children tend to vomit.
What family do noroviruses belong to?
Cliciviridae. Sapporo-like viruses also belong to this family.
Norovirus characteristics
Non-enveloped, single + sense linear RNA genome, replicates in the cytoplasm of the cell in the upper GI tract.
Norovirus transmission
Fecal oral spread, also through fomites
Norovirus incubation
1-2 days, illness lasts 1-2 days
How long does viral shedding persist?
2 weeks
Immunity to norovirus
Short lasting after illness mediated by antibodies, but some individuals seem to be generally resistant to the norovirus
Se-
Secretor negatives. A phenotype due to the mutation in the FUT2 gene.
Other viruses that cause GI symptoms
Enteric adenoviruses, astroviruses.
