Viruses

Question 1

Adenovirus causes

Answer 1

Epidemic keratoconjuctivitis

Rhinitis

Question 2

Capsid

Answer 2

Shell that encloses genome

Question 3

Envelopes

Answer 3

Lipid containing membrane that surrounds some virus particles

Acquired when viral nucleocapsid buds thru cellular membrane during maturation
Budding happens where virus proteins have inserted into host cell membrane

Question 4

Virus are

Answer 4

Obligate intracellular parasites
DNA OR RNA
NO ENERGY

Question 5

RNA virus 3 types

Answer 5

Can be:
Single stranded (+sense or segmented -antisense)
Double stranded segmented
Reverse transcribing

Influenza/ SARS

Question 6

+ sense RNA

Answer 6

Has genome of messenger sense RNA form
+ strand acts as a messenger RNA
Gets translated by hosts ribosome immediately

MAKES PROTEINS

ie. hepC

Question 7

• strand antisense RNA

Answer 7

Must be transcribed with viral RNA dependent RNA polymerase to make + strand which is then translated

Polymerase is found in the capsid
Virus carries its own

Question 8

DNA virus types

Answer 8

SS DNA mostly found in environment
DS DNA ie herpes

Positive strand used as template to make mRNA –> protein

Question 9

Retrovirus

Answer 9

RNA –> DNA via reverse transcriptase

Ie hiv

Question 10

Icosahedral

Answer 10

Capsid structure:
Capsimeres arranged into equilateral triangles
DNA or RNA is in the capsules

Question 11

Helical capsid

Answer 11

Capsomeres are bound to RNA
Coiled into helical nucleoprotein capsid

Spherical shape mostly
Rabies = bullet shape

Question 12

Viral glycoproteins

Answer 12

Are on envelope
Attach virus to target cells
Involved in membrane fusion step of infection 
ANTIGENS
involved w/ neutralizing antibody

Question 13

DNA viruses

HHAPPPy

Answer 13

Herpes
Hepadinovirus
Adenovirus
Papova virus
Parvo virus
Pox virus

Question 14

Properties of DNA viruses

Answer 14

Persistent infection
Transcription is temporally regulated
Genome stays in nucleus
Interact with host transcriptional machinery

Question 15

Characteristics of RNA viruses

Answer 15

Transient
Mostly SS
Mostly enveloped
Mostly helical capsid

Replicate in cytoplasm (except retrovirus n orthomyxovirus)

Exceptions: picornavirus (foot n mouth disease)
Calcivirus (diarrhea)
Reoviridae (diarrhea)

Question 16

Viral replication stages

AUSR

Answer 16

Attachment - followed by adsorption (susceptible to neutralizing antibody) and penetration (insensitive to neutralizing antibody)

Uncoating - release of nucleic acid from capsid

Synthesis and Assembly of viral products - also inhibits host cell mechanisms

Release of progeny from host cell

Question 17

Polyprotein

Answer 17

Host cell ribosomes translate this
Fusion of many viral proteins

Protease cleaves polyprotein
Allows for release is rna polymerase

Question 18

DNA virus replication

Answer 18

1. Converted to early mRNA
   Carries info for enzymes needed for DNA replication
2. Viral DNA replication - late mRNA transcribed from progeny DNA

Question 19

2 types of virion release

Answer 19

Naked or enveloped

Question 20

Transformation

Answer 20

Oncogenes may be introduced and may be uncontrolled and uninhibited cell growth cancer

Question 21

Persistent infx

Answer 21

Ability of evading immune response
Able to attenuate virulence

Adenovirus E3/19K n CMV-US11 block cell surface expression of MHC1 proteins
Thus diminished presentation of viral antigens to cytotoxic T lymphocytes

Pox virus able to encode immunomodulatoeh molecules ie. CrmA - blocks T cell mediated apoptosis is virus infected cells

Question 22

Plasmacytoid dendritic cell

Answer 22

Innate immune response

Recognizes virus and creates soluble proteins - interferons which impede viral replication

Question 23

Type 1 ifn

Answer 23

Principal cytokines in antiviral response

Made by uncleared cells in response to virus

Question 24

Interferons

Answer 24

First active defence against viral infection

Alpha n beta - type 1
Gamma - type 2

Activate antiviral defence in target cells to block replication
Enhance T cell recognition of infected cell

Question 25

Neutralizing antibody

Answer 25

Impt for vaccine mediated protection
Neutralize free virus particles
Do activities against infected cells

HIV is able to avoid neutralizing antibodies