Influenza

Question 1

Influenza genome

Answer 1

Neg. Sense ssRNA => 8 segments

Question 2

Influenza envelope

Answer 2

Host-derived envelope with 2 glycoproteins (Hemagglutinin and Neuraminidase)

M2 ion channel embedded in membrane

Question 3

Nucleoprotein

Answer 3

Covers RNA of Influenza viruses => protection?

Question 4

Viral polymerase complex

Answer 4

Holds together ends of viral RNA
consists of 3 proteins
transcribes -ssRNA to mRNA for translation by host machinery & copy RNA as template = replication

Question 5

Influenza virus life cycle

Answer 5

Entry upon bindingbof HA with sialic acid on cell membrane

Endosome, at low pH e.g. 5.5 => conf change in HA enables fusion woth endosomal membrane

Release genome

import RNA into nucleus

transcription and replication in nucleus

assembly at plasma membrane

Neuraminidase (sialidase) => cleaves interactions btw HA and sialic acid => ensures release

Question 6

Antigenic variability of influenza

Answer 6

diff. subtypes
Infection with one does not protect from infection with other

And variation within subtypes
e.g. H1N1 2005 only weak protection against H1N1 2014

Question 7

Viral pathogenesis

Answer 7

• cell death caused by cytolytic viruses (e.g. influenza destroys respiratory cells)
• immune suppression (e.g. measles)
• immune pathology (Hepatitis B/C) => virus doesn’t kill cells, but reaction to virus by immune system does
• oncogenesis (Hepatitis B/C)

Question 8

What impacts pathogenesis?

Answer 8

Viral strategy (acute, persistent)
Viral tropism (where does virus replicate => respiratory, gut etc
Virus strain
Infectious dose
Host fitness
Host genetics

Question 9

What are viral strategies?

Answer 9

Acute
Latent
Persistent (asymptomatic and pathogenic)

Question 10

What are advantages and disadvantages of mice and ferrets as model organisms?

Answer 10

Mice:
+ low cost
+ transgenic mice
+ immunological reagents => track infection
- don’t reflect disease very well: have to use high doses and causes lower airway tract infection

Ferrets:
+ clinical disease manifestation similar to humans
+ suceptible to unadapted human influenza virus isolates
- complex husbandry requirements
- expensive

Question 11

Polybasic cleavage site in HA

Answer 11

Precursor (HA0) needs to be cleaved into H1 and H2 => connected via disulfide bond

=> marker of virulence

Question 12

Which proteases cleave viral HA

Answer 12

Host cell proteases
HAT (cytoplasmamembrane) TMPRSS2 (cytoplasmamembrane, Golgi)
Furin (Golgi)

HAT and TMPRSS2 limited to respiratory epithelium
Furin ubiquitously expressed in host body

Question 13

HA Cleavage of diff viral strains

Answer 13

Monobasic cleavage site => TMPRSS2 & HAT => local infection (only in respiratory epithelium)
Polybasic cleavage site => Furin => (avian viruses) => systemic infection

Question 14

Transmission of viruses

Answer 14

Vertical transmission

Shedding:
Respiratory secretions
Salvia
Feces
Blood
Urine
Semen
Milk
Skin lesions

Question 15

Animal models for influenza virus transmission

Answer 15

Ferrets
+ display flu-like symptoms
+ transmission pattern reflects situation in humans
- expensive, low numbers of animals

Guinea pigs
+ less expensive, more animals
+/- transmission patterns similar for H3N2 viruses
- do not display flu-like symptoms

Question 16

What types of transmission can be studied?

Answer 16

Contact transmission
Respiratory droplet transmission

Question 17

Transmission of influenza viruses depends on

Answer 17

Temp.
Low temp. favours virus transmission

Humidity
Low humidity favours transmission

Question 18

Vaccines

Answer 18

Biological perpetration that provides immunity against a disease, typically contains a modified form of a pathogen

Goal: faster and less harmful immune response, avoid disease upon encountering a pathogen

Question 19

First vaccine

Answer 19

Smallpox
Milkmaids immune => injected a boy with fluid from lesion of a milkmaid

=> infects boy with smallpox and boy survived

Vaccine led to eradication of smallpox in 1980

Question 20

What are conditions for virus eradication programs?

Answer 20

Virus must have only one host (human specific)
Vaccine must confer lifelong protection

Current programsto eliminate polio and measles

Question 21

What conditions must be met for enabling virus eradication programs

Answer 21

The virus must have only one host (human-specific)
The vaccine must confer lifelong protection

Current programs to eliminate polio and measles

Question 22

Passive immunization

Answer 22

Components of immune response (antibodies) from donor

(Post-exposure e.g. rabies or prophylaxis for immuno-compromised)

Question 23

Active immunization

Answer 23

Induction of a protective immune response in a patient

Question 24

Attenuated live vaccines

Answer 24

Weakened virus
Can replicate and induce potent immune responses but not cause disease in humans and not transmit

=> passage viruses in animals/cell cultures => adaption to other hosts => bring back into humans

Question 25

Rationale design for attenuation

Answer 25

Study pathogenesis of virus => genetically modulate viruses

Question 26

Pros and Cons of live attenuated vaccines

Answer 26

Pros: Potent, long-lived immunity Cons: Transmission of undiscovered viruses from cell line/medium used Viruses may gain back virulence

Question 27

Pros and cons of inactivated vaccines

Answer 27

+Inactivation with formalin or beta-propiolactone is fast and virologically safe - inactivation may lead to alteration in antigenic surface - not suitable for all viruses - inactivating substances often present in injection solution

Question 28

How many doses of vaccines?

Answer 28

Inactivated: multiple boosts Live attenuated: replication, strong immune response after one dose => & more long lived

Question 29

mRNA vaccine

Answer 29

Two doses required Strong antibody and T cell response safe duration of protection not clear yet Chemically modified (not immunogenic => should get translated in cells => reaction to protein) mRNA of vaccine encodes for spike protein => enveloped in lipid nanoparticles

Question 30

Antivirals against

Answer 30

HIV & Hepatitis C (no vaccine available) Herpes Influenza (limited success) Less success than vaccines Not many Most of the ones we have against HIV

Question 31

HIV treatment

Answer 31

Different drug classes inhibit different (all) steps of viral lifecycle Standard triple therapy (usually 2 reverse transcriptase inhibitors and 1 integrase inhibitor) Multiple combinations possible => low chance of resistance and even then there is the possibility to switch to other drugs Control of viral replication, no cure!

Question 32

Hepatitis

Answer 32

Inflammation of the liver HCV can cause chronic infection that increases risk of liver cirrhosis and hepatocellular carcinoma Transmission through blood/sexual contact/vertical transmission

Question 33

Anti-HCV treatments

Answer 33

Previous: INF + Ribavirin (50% success) HCV protease inhibitors + INF + Ribavirin (70-80%) Current: IFN-free, combination of 2-3 HCV protease, polymerase and NS5A inhibitors (95-100% success rate, very few side effects)

Question 34

HepC vs HIV treatment

Answer 34

HIV infection cannot be cleared, HCV can

Question 35

Influenza antivirals

Answer 35

Inhibitors of viral ion channel M2: Amantadine, Rimantadine (also used for parkinson's disease) => block entry: release of genome => **current strains all resistant to M2 inhibitors!** Inhibitors of viral neuraminidase NA: Oseltamivir, Zanamivir, Peramivir, Laninamivir => block release of virus => have to be given **early**! Inhibitors of viral endonuclease PA: Baloxavir: inhibits part of viral polymerase => block transcription