virology Lecture 14- Plant & Animal Viruses

Who discovered the first plant virus?

Martinus Beijernick

• Tobacco Mosaic Virus

• Father of Virology

What is Tulipomania?

• Tulip Breaking Virus (mosaic virus)

• Break color found in Dutch Golden Age

What are some symptoms of Plant Diseases?

• Dwarfing or stunting of plants

• Leaf curling

• Reduced Yields

• Fruit Distortion

• Color Deviations

• Mosaic patterns

• Ring shaped spots are present on leaves

• Wilting

• Withering

• Scaling lesions on trunk and branches

What is chlorosis?

Yellowing of plant leaves (in general)

• Plants infected w/ a virus

What is necrosis?

Rottening/ Dying of a plant

• Colors plant Black

What are the components of tobacco mosaic virus?

• Is helical shaped

• Stable Virus

• +ssRNA genome

• Protein to RNA → 95%

Who helped Martinus Bejinernick find TMV?

• Rosalind Franklin

  • hypothesized TMV particle for hollowness & RNA to be single stranded

What is the range that TMV can infect?

• Commercial crops: Tobacco, Peppers, Tomatoes, Potatoes

• Transmissible to crops e/o

• mechanic transmission mostly

• infectivity can be present up to 2 yrs

What shape do multipartite viruses have?

polyhedron-shaped plant viruses

What plant viruses have envelopes?

Rhabdoviruses & Tospoviruses

What are the commons types of plant viruses genomes?

• +ssRNA, dsRNA, and ssDNA

• Some can have multipartite, (segmented) Quadra, tri, or bipartite

How do plant viruses differ from animals viruses? Benefit?

• package separate viruses into a particle

• removes component for sorting

What disadvantages of plant viruses?

• individual genome segments are packaged into a separate virus particle

  • they are taken up by a single cell

  • large inoculums necessary

What are the plant virus plant cycles?

• enter through a break in plant cell wall → Plasmodesmata

• Have movement proteins, that can move & infect one cell to neighboring cells.

What is local virus spread?

A cell to cell process (slow)

What is a systemic virus ?

Long distance movement from phloem (fast)

Can TMV be controlled?

• impossible to prevent

• reduces crop by 35%

Control Measures for TMV to prevent spread?

• uncontaminated soil for seeding production

• prohibit smoking during work

• ask workers to wash hands frequently

• Destroy/Remove all infected plants from nurseries

• Not mixing plants species in same flower beds (tomato & pepper example)

• Spray plants with milk to reduce mechanical spread

• Rotate crops

CTV

Citrus Tristeza Virus

• when citrus are overgrown

• affects all citrus

Symptoms of CTV

• dieback

• defoliation (loss of leaves)

• stem pitting

• small or poor fruit quality

• stunting

• decline & death

• starvation of the roots

Global Distrubution of the CTV

Global map not common north of world but southernly down

What are the components of the citrus tristexa virus?

• Have a naked helical flexes rod

• +ssRNA genome

  • CP & CPm → 3 VSRs

  • 12 ORFs

  • Frameshift

  • Subgenomic RNAs

How is CTV transmitted and controlled?

• they are transmitted by aphids & gafting

How is CTV controlled usually?

• removal of infected trees

• Quaratunie → import

• Transgenic virus-resistant rootsocks

  • transgene producing siRNAa → target all 3 VSRs to confer complete resistance to CTV in Mexican lime

What are viroids?

smallest pathogens

• naked, circular ssRNA

• don’t encode proteins

  • replicate autonomously when introduced to hosts

What are plant satellite viruses?

-encode their own coat proteins but lack the genes necessary for replication

completely dependent on helper virus fro replication

What are plant satellite RNA or DNA viruses?

• genetic material → little sequence similarity to the helper virus genome

• packaged & replicated by the helper virus

• Example

  • Tomator fried crop destroyed in France → large regions

What are animal viruses?

viruses that primarily affect animals

• may jump the host based on genotype

What are some common infectious pathogens for animals?

• Rabies

• Bat Croonivirus

• PRion (nota. virus)

What is Rabies Virus?

• disease caused by a virus that causes acute encephalitis )inflammation of the brain)

What family does the rabies virus belong to?

• Rhabdoviridae → it can infect a wide variety of hosts through the common reservoirs

  • dogs, bats, raccoons etc.

Refer to structure of Rabies Virus

enveloped etc.

What is the genome organization of Rabies Virus

RNA poly → gene mat.

Glycoprotein → enter of virus into host

M protein→ structure of viurs

P→ assembly of viurs

N protines→ binds to the viral RNA & form nucleocapsid

How is rabies transmitted?

• by saliva from a bite of an infected animal

• incubation period may vary form patient to patinet

• symptoms include but not limited to anxiety delirium, hallucination & hydrophbia

• Post exposure prophylaxis vaccine

BAT coronavirus & transmission

• enveloped +ssRNA virus

• direct contact w/ BAT bodily fluids (saliva, urine, feces)

• Spread from intermediate hosts (civets for SARS-CoV & camels MERS-CoV

• Human activities (wildlife trade, habitat destruction)

What are prions?

causes disease of the nerve & brain tissues (encephalopathy)

• only occurs in mammals

• Transmit orally in food, can happens spontaneously (rare)

• Long Incubation period (years)

  • before encephalitis

• Slow disease, progressive deterioration of brain tissue

• No inflammation → difficult to detect

What are some examples of Animal Prion diseases?

• Scrapie- sheep, goats

• Chronic Wasting Diseases (CWD)- deer, elk, moose

• Bovine Spongiform Encephalopathy (BSE)- cattle

• Transmissible mink encelopahty

What are some human prion diseases?

Sporadic → Creutzfeldt-Jakob disease (CJD)

Familial (Genetic) →

• Fimilia CJD

• GSS → gerstman-straussler-scheinker syndrome

• FFi → Fatal Familial Insomnia

What are some odd components of prions?

• is a viral low molecular weight entity (??)

• resistant o nucleases but not protewases

• no immune response to pahtogens (prions is a host protein)

• Hard to inactivate infectious agent by common sterilants, heat, chemicals, u.v

• Lacking a nucleic acid genome

• Infectious agent is a protein

Who discovered prions?

Stanley Prusiner (nobel prize)

What is the cause of BSE? (Bovine Spongiform Encephalitis)

• Ruminnat tissue in food chain (meat, bone meal etc.)

• alt. theories → human tissue?

What was the spiel of BSE endemic?

• 180k cases in UK

• From recycling of ruminant tissue in food chain implicated

• Progressive decline w/ introduction of feed beans

Refer to map for BSE

more cases had BSE in indigenous animals than from imported animals….

BSE in US

• ban on feeding US cattle meat & bone meal 3 cases to date → RARE

• early 2000s cases arose in us → was there unrecognizable cases?

What is Prion (PrP- Sc)

• pathogenic varianten (Istform) for normal high tune over brain protein (PrP)

• has 2nd structure folding (low frequency, normal PrP) following translation

• may require gene variation → introduces instability but not pathogenicity in normal PrP, to give it an increased propensity to fold into the cytopathic PrP-Sc isoform

What are the potential turnovers of Transmissible Spongiform Encephalopathies Prion disease.

normal PrPc → PrPd (abnormal)

a- helix. B-sheet

How would you diagnosis Prion disease?

• Kinda of can’t

• Post-mortem (pahtology microscopic) molecule testing

• Anetmorem → same technique ^

  • brain biopsy

What is the Chain reaction of Prion disease?

Aberrant Form → PrP- Sc: Prp

catalyzes → PrP-Sc: Prp become PrP-Sc: PrP-Sc

• chain reactions creates an increasing amount of the cytophatic isoform → PrP-Sc

• Can begin with the aberrant form that is introduced to a “normal” susceptible host

  • explain the ritual from eating human brains ^ the consequences

What is Scrapie’s?

• Lognest known prion disease of sheep & goat

• Characterized by abnormal walking, and infected animal scathing against fixed objects

• Example Case: 1961 the scrape agent was transmitted across species form goat to mice, to hamsters

• Helped for researches to understand causes?