(V) 20: Intro to Virology I

Question 1

Pro-MED

Answer 1

Program for Monitoring Emerging Disease

promotes communication btwn international infectious disease community

Question 2

Are viruses organisms?

Answer 2

NO

Question 3

Measles virus

Answer 3

• transmitted in aerosols (cough, sneeze, speaking)
• vaccination = less prevalent in Canada
• still a major problem in certain parts of the world
• vaccine is a cocktail - MMR (Measles, Mumps + Rubella)

Question 4

Measles outbreak

Answer 4

Measles is highly contagious
- most infected ppl were unvaccinated
- patients were not vaxxed due to fear of adverse events from vaccine

Question 5

Ebola virus

Answer 5

deadliest outbreak at the time

we now have vaccine to protect from Ebola

Question 6

Zika Virus

Answer 6

Especially dangerous for PREGNANT women
- transmissible to children in gestation = neurological defects + deformities especially in HEAD shape

links to MICROCEPHALY (baby’s head is smaller than expected)

disappeared for a bit

Question 7

Calicivirus of whale

Answer 7

Causes GI symptoms

• rashes (virus can ooze out of sores into water)
• gastroenteritis

Question 8

Viral genes in genetic code

Answer 8

• viral genetic sequences are integrated into our own genetic material

ex. endogenous retrovirus like HERVs (Human Endogenous Retrovirus)

• endogenous viral sequences are REMNANTS from infections that happened millions of years ago

Question 9

HERVs

Answer 9

Human Endogenous Retroviruses
- in chromosomal DNA

• different from exogenous retroviruses like HIV

Question 10

Levels of Defense Mechanisms

Answer 10

1. Intrinsic - skin, epithelial cells
2. Innate immunity
3. Acquired immunity

Question 11

Polydnaviruses, wasps and caterpillars

Answer 11

GOOD relationships

• wasps lay their eggs inside living insect larva
• when female wasp deposits eggs inside caterpillar, she also deposits her polydnavirus genome sequences
• Innate immune system of larva would normally kill the egg BUT wasp’s expression of viral genes leads to a SYMBIOGENIC relationship that fends off immune system

Question 12

Symbiogenic relationship with wasps

Answer 12

Good relationship btwn wasp and larva

elements of polydnavirus genome expressed by wasp SUPPRESSES the innate immune response of the larva

Question 13

Fungus Curuvularia protuberata

Answer 13

Virus that helps fungus
- permits plant survival

Question 14

Dichanthelium lanuginosum

Answer 14

Plant that grows in extreme temps thanks to infection by fungus

Can grow at temps over 50 degrees C

Fungal thermotolerance is mediated by CThTV (curvularia thermal tolerance virus)

Question 15

Potyvirus

Answer 15

good virus (tulip breaking virus) making nice flowers
- stretched elongated virus
- interferes w/ synthesis of pigments in flowers
- breaks pigmentation in molecules making tulip colours

Dutch would spend 3,000 guilders for a single bulb believed to produce the “beautiful, rare and collection item” broken tulip - 2 coloured

Question 16

MAJOR CONCEPTS IN VIROLOGY (1)

Answer 16

In order for viruses to survive they must:
1. package their genome inside a particle
2. use this particle to transfer their genome from host to host
3. genome contains info to initiate and complete viral infectious cycle
4. genomes establish themselves in host ensuring long term viral survival

THE GENOME IS KEY

Question 17

MAJOR CONCEPTS IN VIROLOGY (2)

Answer 17

1. viral genomes are OBLIGATE MOLECULAR PARASITES
   - they can only function after they REPLICATE in a host cell
2. viruses must make mRNA that can be translated by host ribosomes
   - they use the host protein synthesis machinery to make viral proteins

NO VIRUS CAN TRANSLATE PROTEINS FROM mRNA ON THEIR OWN!!!!!

Question 18

Do viruses grow?

Answer 18

No, viruses do not grow. They replicate

Question 19

Darwin and viruses

Answer 19

Viruses need their host to survive
- so, if viruses killed their hosts, they also would die off/disappear

If the virus did not evade the host defense system, they would never replicate and would die

Question 20

Herpes

Answer 20

To creep or to crawl

Question 21

Tobacco mosaic virus

Answer 21

Ivanovsky and Beijerinck

• crush TMV infected leaves and filter them
• measure debris filtrate to find pathogen

debris applied to a healthy leaf = leaf remains healthy
- debris does NOT cause disease

filtrate rubbed on a new leaf = leaf dies
- agent in filtrate causes disease

Virus: filterable agent that does not grow
- filtrate without a host is USELESS

Question 22

Loeffler & Frosch

Answer 22

discovered first animal virus as an “agent” that caused foot and mouth disease AND was filterable

Question 23

Mimivirus

Answer 23

exception to most viruses

• can be seen under a light microscope
• do not pass through a 0.2 micron filter
• host is amoeba

Question 24

What is a virus?

Answer 24

A virus is a very small, infectious, obligate, intracellular parasite that NEEDS a cellular host