Viruses for Good

Question 1

Describe how parasitoids and hyperparasaitoids work?

Answer 1

the parasatoid will lay her eggs in a responsible host –> the hyperparasitoid will lay her eggs in a double-safe environment –> the parasitdoid baby will emerge –> the hyperparasitoid baby will emerge from the parasatoid

Question 2

how does the parasitic wasp’s eggs safe inside the caterpillar?

Answer 2

parasitic wasps genomes carry the full genome of polydnavirus. The polydnaviruses are made in the female wasps reproductive system and are injected into the caterpillar host along with the wasp eggs. The polydnaviruses are absolutely required to stop the IS of the caterpillar, thereby allowing the wasp eggs to hatch and develop safely inside the caterpillar

Question 3

how do polydnavirus affect the parasitoid’s progeny?

Answer 3

they initiate changes that attract hyperparasitoids, which inject their eggs into the parasitoid larvae

specifically, although parasitized caterpillars continue to feed, polydnavirus infection of the parasitoids changes caterpilllar salilvary products that in-turn changes the “herbivore-induced plant volatiles (HIPVs)” from the plans they eat. The change in HIPVs attract hyperparasitoids.

Question 4

what is required/necessary for the hyperparasitoid to find the caterpillar with parasitoid larvae in them?

Answer 4

polydnavirus

Question 5

how did virus play a role in the formation of mammals placenta?

Answer 5

fusion of synctiotrophoblasts use syncytin; a fusion protein usurped from enveloped retroviruses

sycytin fusion protein on virus induces virus-cell fusion; syncytin fusion protein on cell induces cell-cell fusion

Question 6

Describe how mutine gammaherpesvirus 68 protects mice from bacterial infections

Answer 6

during the window between integration and silencing, mutine gammaherpesvirus 68 induces strong innate immunity that suppresses lethal infections in mice by Listeria monocytogenes – effective 1-4week after gHV68 infection

Question 7

Describe how viruses can promote intestinal homeostasis and shape mucosal immunity similarly to commensal bacteria

Answer 7

when mouse intestinal homeostatic is disrupted by removing the microbiota (germ-free mice or Abx treatment), addition of murine norovirus can restore homeostasis similarly to “good bacteria”. When there’s no virus, abberant intestinal morphology and deficiencies in lymphocyte function occur

Question 8

describe an example of how viruses can protect humans from more-harmful viruses?

Answer 8

the flavivirdiae GB virus C (GBV-C) is prevelent among humans without causing disease. several studies suggest a correlation between GBV-C prevalance and HIV disease outcome… leading to the hypothesis that GBV-C infection could be beneficial.

e.g. Hepatitis G –> slower progression to full-blown AIDS in HIV-1 infected patients

Question 9

Describe the relationship between aphids and densovirus

Answer 9

when rosy apple aphids are infected with densovirus, they develop wings

pea aphids usurped the densovirus genes to induce wing formation in a virus-independent manner

Question 10

how are baculovirsuses used in insect control?

Answer 10

1. nucleopolyhedrovirus occulsion boseis (OBs) are mainly comprised of crystalline polyhedrin that surrounds ODVs
2. during primary infection, OBs are solubilized in the insect midgut and release ODVs that pass through the peritrophic membrane and fuse with midgut epithelial cells
3. BVs enter non-midgut cells and bud out
4. larvae dies and the larval tegument reptures are releases OBs that contaminate the foliage for for futher cycles

Question 11

how can baculoviruses be used to express high levels of proteins for many applications? what are the benefits

Answer 11

1. the polyhedrin gene is replaced by the gene of interst (GOI), co-transformed into bacteria with the baculovirus genome
2. the genome into which the GOI integrates by recombination
3. the recombinant baculovirs plasmids the transfected into insect cells, to produce baculoviris particules that can then be used to infect insect cells and produce very high concentrations of the protein of interest

benefits: rapid, high protein levels, similar post-translational modification because euk cells

Question 12

how can viruses be used to study protein-protein interactions?q

Answer 12

retrovirus gag is sufficient to make VLPs. One way to test if proteins ‘X’ and “Y’ interact, is to fuse “x” to the gag protein. when gag makes VLPs, if X interacts with Y, then Y will be carried into the VLP

Question 13

how do some vaccines for HPV use baculovirus?

Answer 13

make baculovirus express the HPV L1 major capsid protein, which self-assembles in to VLPs

Question 14

how do we use virus proteins as tools to make vaccines?

Answer 14

lipid nanoparticles (LNPs) can deliver RNA, DNA, drugs to cells. to make LNPs fuse to cells and become more efficient, the “fusion-associated-small-transmembrane” (FAST) proteins of the non-enveloped reovirus are applied

non-enveloped fusogenic reoviruses make a tiny membrane fusion protein “FAST” to fuse infected cells to nearby uninfected cells (hide from Abs)

Question 15

how is TMV used for imaging to detect early atherosclerotic plaques?

Answer 15

plaques are rich in S100 calcium-binding protein A9 (S100A9)

1. the coat protein of TMV can be linked to S100A9 targeting molecule on the external lysine amino group to target to athersclerotic lesions
2. then a contrast agent such as a fluorescence molecule can be chemically linked to the intra-viral glutamic acid carboxyl group for detection

Question 16

what are the advantages for using TMV over conventional imaging dyes? whats the advantage of filamentous viruses? whats a disadvantage?

Answer 16

TMV vs conventional dyes

1. targeting
2. contrast agent
3. repeated units = more power
4. uniform
5. very stable (pH, temperature)

advantage of filamentous viruses: prevent phagocytosis and more repeated units –> even more power

disadvantage: immunity to virus backbone

Question 17

how can reactivtion of endogenous retroviruses be used in cancer detection and prognosis?

Answer 17

human endogenous retroviruses (HERVs) make up 8% of our genome. HERVs are commonly inactivated in normal cells. Epigenetic changes such as loss of DNA methylation in cancers leads to expression of HERV mRNAs. These can function of markers for cancer and can also promote anti-tumoral immunity via

1. HERV-derived cell surface Ags are seen as foreign by B cells
2. presentation of HERV-derived T-cell Ags
3. stimulate “virus-like” response –> interferons

Question 18

Describe how phage therapy was used in WWII

Answer 18

• staph and strep bacteriophages were distributed to soldiers. First few hours when bacteria were still on the wound surface
• lack of hygiene in the field conditions and lack of penicillin production in russia, so phages that destroyu bacteria causing intestinal infection such as cholera, typhoid, dysentery, salmonellosis were used en mass
• Battle of Stalingrad: cholera was high. to obtain cholera to grow phage – corpses were stolen and carried over front lines by soviet scouts - too week. Used rabbits and finally made enough…but train carrying the phage was bombed. So they establishes an underground secret lab in Stalingrad to make cholera phage directly

Question 19

do you want a temperate or virulent phage for phage therapy?

Answer 19

temperate - lytic cycle under specific conditions

virulent - always lytic

don’t use temperate phages: only lytic under specific conditions; horizontal gene transfer of virulent or resistant genes

Question 20

what are the benefits of phage therapy relative to Abxs or alternatives?

Answer 20

• can target G- and G+ bacteria
• specificity (no risk of destroying other normal microbiome in the body)
• self dosing
• less likely to cause resistance compared to tranditional antibiotics because of their selective killing ability and co-evolution with host bacteria (the mutation rate of phage is faster than that of host-bacteria)
• phage are abundant in nature and the corresponding phage can be generally found in the environment containing a certain pathogen

Question 21

what are some challenges of phage therapy relative to Abx or alternatives?

Answer 21

• too much specificity = limited spectrum
• phage are often lysogenic
• delivery to infection site
• immune recognition over time
• evolution of phage resistance

Question 22

how can phage cocktails be used to improve phage therapy? give an example

Answer 22

• overcome narrow phage lysis spectrum
• delay resistance

phage cocktail reduces [c. diff] and prolongs survival in syrian golden hamster model of acute c. diff infection

Question 23

how can we engineer phages if they’re lysogenic? use CF example

Answer 23

researchers screened a library of phages –> screeening identified Muddy that efficiently kills GD01; ZoeJ infected GD01 but appeared to be temperate –> a lytic derivative of ZoeJ was engineered by recombination to remove its repressor gene –> now lytic towards GD01 –> BPs and its lytic derivative infected GD01 poorly, they isolated a host range mutants that efficiently infects GD01 and retained specificity

first did a topical wound test – no AEs –> IV therapy every 12h for 32 weeks –> lung function improved + phage replicated then diminished

Question 24

how can phage-antibiotic synergyy occur?

Answer 24

AMR in p. aerugenosa is caused by the efflux pump (oprM) –> phage OMKO1 binds through the oprM –> selects bacteria with no/less oprM –> susceptible to Abx and resistant to phage

in CF patient: restored lung function, didn’t completely clear bacteria, but bacteria left behind were Abx sensitive