Microbiology - Enterovirus

Question 1

Virus

Answer 1

Obligate intracellular parasite with simple “life” cycle.

Upon replication, makes copies of themselves using host cell machinery.

Question 2

Virion

Answer 2

Extracellular version of a virus.

Question 3

Virus structure

Answer 3

1. Nucleic acid = genome
2. Capsid (icosahedral or helical) = protein coat
3. Envelope = lipid membrane

Question 4

Virus classification (7 things)

Answer 4

1. RNA or DNA
2. SS or DS (single strand or double strand)
3. Positive sense (same as mRNA and can be directly translated to protein inside the host)
   Negative sense (complementary to mRNA, so need to go through transcription before translation into protein).
4. Capsid symmetry (icosahedral or helical)
5. Presence or absence of envelope.
6. Mode of replication.
7. Tropism (which tissues it affects)

Question 5

Detection of physical components of virion or viral antigens (5 things)

Answer 5

1. Electron microscope to detect virions.
2. PCR or hybridization to detect nucleic acids.
3. Enzyme assay to detect viral enzymes.
4. Immunofluorescence to detect viral antigens.
5. Hemagluttination - viruses cross-link and agglutinate RBCs.

Question 6

Detection of infectivity of a virus (2 things)

Answer 6

1. Observe production of disease in an animal.

2. Observe the cytopathic effect (changes in host cells due to virus)

Question 7

Detection of Virus-specific antibodies (4 things)

Answer 7

1. ELISA (more screening because not very specific because only looking for response to one viral antigen)
2. Immunoblot/Western blot (more specific and for confirmation because looking at variety of virus’s antigen - infected patient will have antibodies that bind to many antigens of the virus on the gel)
3. Hemagluttination-inhibition : antibody binds to virion and not RBCs.
4. Latex bead agglutination assay.

Question 8

Replication of Virus (8 steps)

Answer 8

1. bind to cell surface receptors
2. entry across plasma membrane
3. uncoating
4. transcription of mRNA (if negative sense)
5. translation of viral proteins
6. amplification of genome (DNA/RNA replication)
7. assembly of virions
8. egress

Question 9

Viral entry mechanisms (2)

Answer 9

1. fusion with plasma membrane (virus’s envelope is same as plasma membrane, so envelope gets incorporated into plasma membrane and virus is free inside the cytoplasm)
2. receptor-mediated endocytosis (with clathrin coated pits and lysosome via low pH/acidity)

Question 10

Infection of host organism (6 steps)

Answer 10

1. entry
2. primary replication at site of entry.
3. primary viremia (spread to other parts of body thru blood stream)
4. secondary replication
5. clearance by the host or persistence
6. Release from host and transmission to other hosts