Week 3: i. Virology

Question 1

History:
Edward Jenner -

Answer 1

pioneer of smallpox vaccine (1796)

Question 2

History:
Louis Pasteur -

Answer 2

Louis Pasteur - created 1st vaccine for rabies (1885)

Question 3

History:
Adolf Edward Mayer -

Answer 3

Adolf Edward Mayer - published paper discussing filterable infectious agent that caused dis in plants (1886). Dismissed

Question 4

History:
Dimitri Ivanofsky -

Answer 4

Dimitri Ivanofsky - demonstrated filterable infectious agent; showed sap of leaves infected w tobacco mosaic disease retained its infectious properties after filtration

Question 5

History:
Martinis Beijerinck -

Answer 5

Martinis Beijerinck - filterable infectious agent able to multipl in living cells - “contagious living liquid”

Question 6

True or False,
Viruses infect ALL cellular life forms and are found in soil, air and water

Answer 6

True

Question 7

Viruses in the human host:
- Non- pathogenic:

Answer 7

Human Virome (viral microbiota) - NB for metabolic homeostasis

Question 8

Viruses in the human host:
- Pathogenic:

Answer 8

Quiescent (inactive)/ Active: infection/ disease

Question 9

What is a virus?

Answer 9

Question 10

What is a virion?

Answer 10

Virion = complete infectious viral particle.

Question 11

What is a virion composed of? (4)

Answer 11

Composed of:
1. outer coat (envelope); capsid;
2. genome - nucleic acids (allows for replication).
3. Envelope — lipid membrane that encloses the nucleocapsid and has surface proteins - glycoprotein which are antigenic = induce immune response.
4. Capsid — protein shell that protects the genome; present in both enveloped and non-enveloped viruses; in non-enveloped = outer covering; in enveloped = underneath lipid membrane

Question 12

Types of Virus Structure: (4)

Answer 12

Question 13

What are the properties of enveloped viruses? (3)

Answer 13

Question 14

What are the properties of naked viruses? (5)

Answer 14

Question 14

The Genome:
DNA: (3)

Answer 14

• Single stranded ie Parvovirus
• Double stranded (most) ie HAdV, HPV, polymviruses, herpes viruses, pox viruses
• Reverse transcribing ie Hep B virus

Question 15

The Genome:
RNA: (5)

Answer 15

• Double stranded ie Rotavirus
• Single stranded ie all other viruses
• Segmented — reassortment/ recombination ie rotavirus, influenza viruses, Bunya viruses, Arenaviruses
• Non-segmented — all other RNA viruses
• Reverse transcribing ie HIV

Question 16

What is the Baltimore classification system?

Answer 16

Question 17

Spread of viruses
- Mode of transmission: Respiratory droplet (inhalation)

• Examples:

Answer 17

Question 18

Spread of viruses
- Mode of transmission: Fecal-oral (ingestion)

• Examples:

Answer 18

Question 19

Spread of viruses
- Mode of transmission: Blood and blood products/percutaneous/organ transplant

• Examples:

Answer 19

Question 20

Spread of viruses
- Mode of transmission: Sexual

• Examples:

Answer 20

Question 21

Spread of viruses
- Mode of transmission: Skin or mucous membrane contact

• Examples:

Answer 21

Question 22

Spread of viruses
- Mode of transmission: Zoonoses (bite; direct contact)

• Examples:

Answer 22

Question 23

Spread of viruses
- Mode of transmission: mother-to-child

• Examples:

Answer 23

Question 24

Previous classifications: (3)

Answer 24

Question 25

International committee on taxonomy of viruses (ICTV):

Answer 25

Question 26

Viral Pathogenesis: (2)

Answer 26

- Entry into host - Primary (localized) replication - permissive cells (@ pt of entry)

Question 27

- Viremia:

Answer 27

virus goes into transport systems and infects other cells/ invades other system to

Question 28

- Viremia = Primary:

Answer 28

lymph and reticular endoplasmic systems

Question 29

- Viremia = Secondary:

Answer 29

haematogenous/ neuronal

Question 30

Viral Pathogenesis - Systemic replication:

Answer 30

virus goes to target organs ie CNS, CVS, Liver

Question 31

How does viral replication take place? (5)

Answer 31

1. Attachment of virion to a cell - receptors = virus specific 2. Entry and unloading into cell - endocytosis/ fusion 3. Synthesis of viral genes - transcription of viral genes into mRNA; translation of viral mRNA into proteins and genome replication 4. Assembly of viral genome and proteins into virion 5. virus release - cell lysis or budding

Question 32

Outcomes of viral infection:

Answer 32

Question 33

What is the spectrum of viral infections?

Answer 33

Question 34

How to diagnose viral infections: Need correct specimen; correctly collected ; correctly transported and correct test to ensure accurate diagnosis Viral diagnostics: (2)

Answer 34

1. Serology 2. Molecular assays/ PCR

Question 35

What is the method of serology? (2)

Answer 35

1. Serology - detection of Ab against spec Ag - Speciment - blood/ serum: IgM - diagnosis of acute infection; IgG - indicate immunity (from past infection or vaccination)

Question 36

1. Serology Benefits: Disadvantage:

Answer 36

- Benefits: cost effective; sensitive; specific; automated testing therefore quick results; doesn’t req viable virus - Disadvantage: may have false results (due to interfering substances)

Question 37

What are molecular assays/PCR? (3)

Answer 37

- detection of viral gene - RNA/ DNA - variety of specimen ie CSF, blood, swaps, urine - Qualitative ie positive/ negative + Quantitative ie tells viral lode

Question 38

2. Molecular assays/ PCR Advantage: Disadvantage:

Answer 38

- Advantage: high sensitive; fast and automated; can culture viable/ unviable specimen - Disadvantage: can have false positive due to contamination or degradation

Question 39

Health implications of viral infections: - Human diseases: (3)

Answer 39

- Minor illness - common cold - Lethal disease - rabies, VHFs and causes of cancer - Pandemic diseases - HIV, H1N1-2009

Question 40

Health implications of viral infections: Domestic animal disease -

Answer 40

may spill over to humans

Question 41

Health implications of viral infections: Research and Diagnostics: (4)

Answer 41

- molecular and cell biology - dev of vaccine - treatment (anti-cancer agents, gene vector for treatment of genetic diseases) - source of enzymes used in molecular biology