Influenza

Question 1

Few facts about influenza

Answer 1

• segmented -ssRNA virus (8 segments, 10 proteins)
• three types
  
  • A causes disease in humans and many animals —> cause for pandemics
  • reservoir for A are wildbirds and its zoonotic
  • B causes disease only in humans
  • C causes disease in humans and pigs
• antigenic shift (segment reassortment)
• antigenic drift (mutations)

Question 2

Influenza in birds

Answer 2

low pathogenic avian influenza (LPAI):
- no or mild disease, drop in egg production
- HA cleavage in lung
H1-H16

high pathogenic avian influenza (HPAI)
- severe disease -> lethal
- aggressive clinical course also for humans
- systemic infection -> HA can be cleaved systemically (more basic AAs)
H5, H7

Question 3

What are models for infections of the lung?

Answer 3

• Animal:
  1. mice
  2. ferret
  3. guinea pig
  4. non-human primates
• cell culture
• embryonated chicken eggs
• organoids

Question 4

Mice as a influenza model

Answer 4

• very common (easily to manipulate, rapid reproduction, low cost, stable genome)
• good sign of disease is weight loss
• hypothermia instead of fever
• no transmission studies possible (no coughing and sneezing)
• infection intranasal or intratracheal

Question 5

Which mice strains are used for influenza models?

Answer 5

• wild type
• BALB/C for pathogenicity studies
• C57BL/6 as transgenic mice
• DBA/2J and DBA/J are highly susceptible to viral infections

Question 6

What is Mx1 for?

Answer 6

• under transcriptional control of IFN
• wildtype Mx1+/+ is highly resistant against Influenza A
• Mx1-/- (standard lab mice) is susceptible

Question 7

Which humanised mice are used as an influenza model and what are they used for?

Answer 7

• human immune system (HIS) -> hematopoetic stem cells
• bone-liver-thymus (BLT) -> hematopoetic stem cell + BLT
• human liver (HuHEP)
• BLT-L -> BLT + lung cells

used for: vaccine and drug studies

Question 8

mice vs human

Answer 8

• easy to handle and breed
• well characterised immune system
• respiratory physiology is different (SA α2,3 in mice vs. α2,6 receptor in human)

Question 9

the ferret model

Answer 9

• gold standard
• allow for transmission studies
• infection intranasal, intratracheal or via aerosols
• airways very similar to humans
• lack of reagents makes research hard and expensive

Question 10

the guinea pig model

Answer 10

• Dunkin Hartley strain is used
• infection intranasal, intratracheal or via aerosols
• no mortality
• virus replicates in upper respiratory tract (mainly α2,3 SA)
• lack visible symptoms

Question 11

non-human primates model

Answer 11

• most physiologically similar to humans
• used for immune response and pathogenesis
• expensive

Question 12

What are the cell culture models for influenza studies?

Answer 12

Madin-Darby Canine Kidney (MDCK)
- express both SA on surface
- used for virus isolation and growth kinetics

african green monkey kidney (Vero) cells:
- used to propagate, isolate and grow the virus
- pathogenesis study

human lung carcinoma (A549) cells:
- study interaction of influenza and human cell as well as viral replication
- highly susceptible to influenza

primary human respiratory epithelial cells:
- most physiologically relevant
- used for replication study, immune response, drug and vaccine screening

Question 13

Embryonated chicken eggs

Answer 13

• used for vaccine production
• virus can replicate in allantoic

Question 14

2D organoid cultures

Answer 14

• derived from primary respiratory epithelial cells or iPSCs
• cultures grown in transwells

Question 15

3D organoid cultures

Answer 15

• derived from primary respiratory epithelial cells or iPSCs
• culture dish is coated with an ECM material
• more closely resembles the complex structure of human respiratory system