influenza

Question 1

antigenic drift

Answer 1

same subtype keeps circulating in the population with some point mutations
influenza A and B

Question 2

antigenic shift

Answer 2

soudent apeurante of a new subtype that replace the circulating virus
you see some gene segment reassortment
only influenzaa A

Question 3

all influenza viruses bind

Answer 3

to the silica acid termini of cell surface glycans
eg: avian viruses is specific form 2-3 linked silica acid
human influenza for 2-6

Question 4

ARDS

Answer 4

acute respiratory distress syndrome
immunopathoglogy due to massive production of pro inflammatory cytokine

Question 5

strategies to deal with influenza

Answer 5

1) vaccination of high risks group but this come with limitation as the vaccine need annual updating and is hard to produce, as well as with a 60% efficacy

2) antiviral therapy is possible for high risk group when hospitalized and during pandemic

however antivirals are needed in different setting:
as pandemic prophylaxis, a pandemic treatment, in sporadic treatment of avian influenza and for seasonal flue In high risk groups such as pregnancy immunocompromised and over 65

they also serve different purpose: suppress disease in fragile person, r in healthy people. Can prevent virus spread.

Question 6

antivirals for seasonal use

Answer 6

it is easy to administer and has very few side effect. It has a long therapeutic window with a very defined mode of action. It is safe regarding resistance and give a higher efficacy when used in combination.

it is active against flu A and flu B as well as all flu A HxNx subtypes

Question 7

example of antivirals

Answer 7

amantadine and rimantadine which are M2 ion channel inhibitor however it is not active against influenza B

neuraminidase inhibitor such as oseltamivir and zanamivir are the only one used widely in seasonal influenza. These prevent release of visions

Question 8

why does amantadine only work on influenza A?

Answer 8

its because influenza A has hydrophobic residues that allow binding of the agent while the polar residue of influenza B prevents it.

Amantadine has some CNS side effect and unfortunately the virus has developed very fast resistance against the compound so it is basically useless

Question 9

Neuraminidase inhibitor

Answer 9

Neuraminidase need to cleaves silica acid termini in the receptor to release new visions. Inhibitor makes the visions to stick at the surface

it inhibit all influenza viruses including B and avians. This even when neruminidase is prone to sequence variability due to antigen shift and drift. its beaches NAI interact with the conserved catalytic pocket by mimicking the sialyc acid binding

the primary use of these is in risk patient in particular hospitalized patient.

it works better when used at early onset

it should not really be used as a board population antivirals

resistance is however possible. Suboptimal dose of tamiflu can lead to resistance. It is seen faster with olsetamivir (due to the different binding mode ). The virus do so by:
réarrangement of amino acid in the neuraminidase active site is needed to accomodate for the drugs. So mutation preventing the rearrangement can lead to resistance and mutant visions can therefore still bind to the receptor and the drugs.

Question 10

use of ribavirin

Answer 10

normally used against herpes virus, it is an inhibitor of cellular IMP dehydrogenase, so there few chance that resistance developed
it has a broad anti-RNA virus activity:)
some SE are seen such as anaemia during long term used but for influenza it would only be used short term

Question 11

Trial design for drug candidates

Answer 11

First need to check PK and tolerability in healthy volunteer. Then we challenge healthy person with the virus. You can then try it in seasonal flu in non hospitalized patient.
phase 3 is multi centered and is trialled in uncomplicated influenza in healthy kind of people
lastly it is used on person at risk.

Endpoints in uncomplicated patient are the symptoms scoring, the time until cure and the viral loads in discharge.
In hospitalized patient, it is the duration of hospitalization, the nomrlisation of vital signs, the need for oxygen and of course mortality.

Question 12

inhibitor of viral entry

Answer 12

Fludase works on the cell receptor
bnAbs on haemaglutinin.
HA mediates the virus attachment top syalilated receptors
acidification of the endosome leads to a conformational change in HAinto a trimers which allow fusion with the membrane of the endosomes.

HA is made of a globular heads with receptor binding site and of a stem with a fusion peptide.

inhibition has been very challenging because there is different receptors used by avian and human influenza virus. You do see more variation I the globular heads then the stem.

HA has a very week interaction with syalic acid. Currently in trial are broadly neutralizing anti HA antibody which would cover the HA and ok for all subtypes.
Another one would be fusion inhibitor but that would be subtype specific.

Question 13

influenza replication

Answer 13

particles bind to the cell surface silica acid. The particles are internalized by receptor mediated endocytosis into endosome. The loupe environment activates the M2 channel. the protons induce uncaring. The HA is then acid triggered into conformational change that leads to the fusion of the viral and endosomal membrane. the NC is then released in the cytoplasm where the viral ribonucleotides are dissociated from each other and from the m1 proteins. the viral ribonucleotides are the rapidly transported to the nucleus through the nuclear pores.

Question 14

Fludase

Answer 14

recombinant fusion proteins. It basically cleaves off both 2-3 and 2-6 lines of salicylic acid, which destroys the virus receptors. It is currently in phase 2 clinical trial but direct phase 1 anti fludase antibodies led to adverse respiratory events.

Question 15

broadly neutralising antibody

Answer 15

hese broadly neutralizing antibodies generally target conserved functional regions on the major influenza surface glycoprotein hemagglutinin (HA). The characterization of their neutralization breadth and epitopes on HA could stimulate the development of new antibody-based antivirals and broader influenza vaccines.

to discovers these you first need to screen a large antibody libraries from B cell donor after flu vaccination, after flu infection and phage display method.
You then identify the bnAB that are active against group 1, group 2 and both
you show that they work in influenza virus infected mice.
you then do cocrystalisation to identify the HA binding site.

Question 16

mode of action of blabs anti HA

Answer 16

(a) by blocking binding to sialic acid residues on the surface of the target cell; (b) by inhibiting endosomal viral fusion; (c) by preventing release of progeny virions from infected cells; (d) by inhibiting extracellular proteolytic cleavage of HA

The mode of viral neutralization depends on the site recognized on the trimeric HA. Thus, while anti-head antibodies work primarily by inhibiting viral entry (they are detected by the classical hemagglutination inhibition assay, HAI), anti-stem antibodies do not block binding to sialic acid (they are inactive in HAI), but instead prevent endosomal viral fusion, viral budding or HA cleavage activation

so you either developed Fab or Fc antibody target.

Opsonophagocytosis represents another important Fc-dependent mechanism for antibody-mediated clearance of virions and infected cells (ADCP), mainly by alveolar macrophages [75]. A recent study showed that antibodies unable to induce ADCC and CDC were highly effective in ADCP, suggesting that for some antibodies phagocytosis could be the major mechanism of protection which leads to promotion of clearance

Question 17

boards small-molecule fusion inhibitor

Answer 17

they act as a glue on the HA trimers which prevent refolding at ph5 however it as a narrow activity against a few HA subtypes

Question 18

inihibitors of the viral polymerase

Answer 18

it is an excellent target as it is indispensable for viral replication, it is highly observed among virus subtypes.However catalytic site inhibitors could have a high resistance barrier.

the polymerase trimer is made of a PB2 (cap binding), PB1 (polymerase active site) and PA (endonuclease active site)
vRNA is a panhandle structure protected by a nucleoprotein.

transcription is assured by cap binding of PB2, cleavage by PA and primer elongation by PB1.

The actual polymerizing function for viral RNA synthesis comes from the PB1 subunits. the replication of vRNP proceed ia complementary RNP intermediates which act as a template for vRNA synthesis

inhibitors can block PB2, PA or PB1 (these are nucleoside analogs).

an exemple of PA inhibitor is baloxavir with has a broad spectrum. The inhibitor makes PA less flexible . It chelate the metal co factors in influenza virus polymerase

Question 19

PA inhibitor

Answer 19

an exemple of PA inhibitor is baloxavir with has a broad spectrum A and B. The inhibitor makes PA less flexible . It chelate the metal co factors in influenza virus polymerase

it allows to decrease the time before alleviation of symptoms and decrease the viral loads. However, resistance develop in more than ten percent of patients, usually in influenza A. Virus rebound have been seen and the mutant virus are transmissible so the patients have to be very closely monitored. it is not longer used

Question 20

PB1 inhibition

Answer 20

exemples are favipivir and monupiravir.

these nucleoside inhibitors are a challenge. because they require activation by kinases. and they end up in completions with cellular ribs NTP. Another challenge is that they posses RNA-mutagenic potential.

The pro are that they interact with the catalytic site of the polymerase, they have a broad activity and resistance against these seems to be slower. Falvipiravir has been approved in Japan and still in phase 3 in Europe and US. It seems to have a broads RNA virus inhibitor and acts by non obligate chain termination but can also be incorporated into RNA. it contains pseudo bases that mimics A and G, which gets recognize by GTP and ATP. At high concentration its great and terminates viral RNA synthesis, but at low it seem it can get integrated and leads to viral mutagenesis

Molnupiravir has shown an excellent safety profile against covid 19 but resistance barrier data have not been published and seems to induce mutations in the RNA genome of the virus.
It mimics Cytosine and uracil and block the replication.

Question 21

PB2 inhibitor

Answer 21

Pimodivir blocks the cap binding domain by binding to the phenyl alanine amino acid in the very hydrophobic pocket. minimal cap analogue
However only in influenza A cause influenza B has less phenylalanine in the pocket

very potent inhibitor however it is not effective for patient hospitalized with influenza A when comparent to standard of care treatment.