Norovirus

Question 1

few facts about norovirus

Answer 1

• no zoonosis, but viruses that infect animals
• non enveloped icosahedral
• • ssRNA
• responsible for majority of GI infections (acute infection) -> AGE
• short incubation time
• asymptomatic shedding for 4 weeks
• causes epidemic viral gastroenteritis

Question 2

genotypes

Answer 2

• defines the species tropism
• G1, G2 (also pig) and G4 (also cat) are human
• G5 is mice

Question 3

how does norovirus enter the cell?

Answer 3

• attachment to HBGA (histo blood group antigens)
  —> results in restriction of strains to certain HBGA

Question 4

What are the animal models for norovirus?

Answer 4

1. chimpanzee (not allowed anymore)
2. gnotobiotic pigs (born under sterile condition)
3. mouse (MNV or humanized mice)
4. zebrafish

Question 5

Chimpanzee model in more detail

Answer 5

• only i.v. infection (nor natural)
• no disease but immune reaction
• good for vaccine development

Question 6

Gnotobiotic pig model in more detail

Answer 6

• mild disease
• fecal shedding
• seroconversion
• limited facilities

-infection p.o. with human/pig feces (G2)

Question 7

Mouse model in more detail

Answer 7

• infection with murine norovirus (can be cultivated)
• high prevalence in research colonies (high contamination)
• don‘t bind HBGA
• no vomiting
• MNV infects macrophages and DCs

Question 8

Inflammatory bowel disease

Answer 8

• can be triggered by norovirus (also in mice by MNV)

Question 9

Humanized mouse model

Answer 9

1. hu-HSC mouse: irradiation & injection of CD34+ hHSC (hematopoetic stem cell)
2. BLT mouse: irradiation, implantation of human fetal thymus & injection of autologous CD34+ hHSC

• humanised mice show signs of disease and shed virus, non-humanised can only shed

Question 10

Zebrafish model in more detail

Answer 10

• model organism for many viruses
• cheap
• remarkable similarities to humans (genetics, physiology & pharmacology)
• can make HBGA

Question 11

Cell culture models for HuNoV infection

Answer 11

1. 3D organoid model
   
   • limited cell viability, accepted system, no immune cells, donor matters (HGBA), natural tropism
2. B cells
   
   • non-natural tropism, simple, optimal with soluble HBGA
3. 3D culture system „organoid“
4. salivary glands

non can produce virus stock

Question 12

Which part does the microbiota play during HuNoV infection?

Answer 12

• noroviruses bind to bacteria with HBGA-like structures
  —> can enhance infection
  - it also protects norovirus from heat stress
• E. cloace facilitates infection of B-cells

Question 13

Cell types of the small intestine

Answer 13

differentiation from crypt to apical top

5. microfold (M-) cells (transport organisms and particles from lumen to immune cells)
6. panted cells (secrete antimicrobial peptides)
7. goblet cells (epithelial cells that secret mucus)
8. intestinal epithelial cell (single layer, non-ciliated, columnar)
9. stem cells at base of crypt

Question 14

How to create an organoid (enteroid/colonoid)?

Answer 14

• culture of intestinal crypt
• culture of human pluripotent stem cells + differentiation factors for endoderm
• not easy and expensive but reproducible