Viruses for good

list the ways natures symbiosis uses viruses for good

• rosy apple aphid + densovirus

• pea aphid + densovirus

• parasitic wasp carry genome of polydnaviurs (PDV

• parasitoids + hyperparasitoids

describe the example of apple aphids

Rosy apple aphid depends on densovirus for transcriptional induction of wing genes → depedns on virus for propagaibtion

• when born, has no wings, as grows and crowds, virus spreads and induces proteins that induce chromatin changes to make babies with wings → can fly and spread to new plant

describe the example of the pea aphids

Pea aphid usurped the densovirus genes to induce wing formation in a virus-independent manner!

• endogenized the virus → is now in its own genome, under stress the promoter induces production of winged offspring

describe the example of parasitic wasps

Parasitic wasps genomes endogenously carry the full genome of polydnavirus (PDV). The PDV are made in the female wasps reproduction system, and are injected into the caterpillar host along with the wasp eggs. The PDVs are absolutely required to stop the immune system of the caterpillar, thereby allowing the wasp eggs to hatch and develop safely inside the caterpillar.

• without virus, caterpillar IS would recognize wasp eggs and destroy them

describe the example of parasitoids and hyperparasitoids

The hyperparasitoid “actively” chooses the parasite-inoculated host!

• learned to recognize injected insects → symbiotic PDV and venom reveal parasitoid to its hyperparasitoid

describe an example of viruses being involved in the evolution of organisms

mammals placenta: Fusion of syncytiotrophoblasts uses syncytin; a fusion protein usurped from enveloped retroviruses

• need effective wall between you and fetus → one large cell covers whole placenta (syncytia) → cells fuse togther

• syncytin fusion protein on virus induces virus-cell fusion

• syncytin fusion protein on cell induces cell-cell fusion, became endogenous

describe the example of viruses possibly protecting from bacterial infections

During the window between integration and silencing, murine gammaherpesvirus 68 induces strong innate immunity that suppresses lethal infections in mice by Listeria monocytogenes

• mice given gHV68 then Listeria challenge 4-weeks later had much higher survival

• just because it ‘can’ doesn’t mean it ‘does’ → doesn’t represent human scenario

describe the example of viruses potentially protecting us from more harmful viruses

The Flaviviridae GB virus C (GBV-C) is prevalent among humans without causing disease (2% of blood donors are viremic with GBV-C and 13% are seropositive to GBV-C E2 protein). Several studies suggest a correlation between GBV-C prevalence and HIV disease outcome…. Leading to hypothesis that GBV-C infection could be beneficial…

• took longer to progress to AIDS with HepG → is that actually something to do with HepG? maybe whatever makes them susceptible to HepG also prevents AIDS progression?

list the examples of viruses in agriculture and plant biotechnology

• apple latent spherical virus (ALSV)

• Baculoviruses

how are apple latent spherical viurses (ALSV) being used?

Apple latent spherical virus (ALSV) expressing genes that induce flowering, are being developed to promote flowing of slow-to-flower plants where the flowers have medicinal (or other) applications

• plants have triggers that increase TF FT to allow flowering → FT binds and turns on flowering genes

• ALSV has 2 diff RNS, inserted FT protein into RNA 2 → when given to plant, bypasses need for triggers

• coat gold particles in virus RNA, use gene gun to force its way into plant

how are baculoviruses used?

insect control: insect virus, very specific virus for specific insect

• available for most insects, specific for given insect, polyhedron-occluded virions stable for up to 25 years

• polyhedron occludes virus into ‘pellet’, which gets eaten by the insect, virus replicates in insect and creates many more polyhedrons, virus is pooped out in crystals, which are stable and tasty to other bugs

• used in agriculture