Introduction to Virology (Final Exam)

Viruses are ______ replicating.

self

Why must viruses infect cells?

- Don't have a metabolism

- Lack growth requirements

Viruses have linear ______ or ______ cores.

ssDNA, ssRNA

Viruses have a ______ around their nucleic acid core.

capsid (helical, icosahedral, complex)

The ______ is the particle that infects other cells.

virion

The family name for viruses is ______.

-viridae

What are the steps of viral infection of host cells?

1. Attachment

2. Penetration

3. Uncoating

4. Replication

5. Assembly

6. Release

When uncoating occurs, the ______ is freed from the viral capsid.

nucleic acid

What is the process of replication?

+RNA --> DNA --> RNA --> dsRNA --> dsDNA

RNA viruses replicate in the ______, while DNA viruses replicate in the ______.

cytoplasm, nucleus

A positive sense RNA strand is ready to ______.

replicate

Negative sense RNA strands require an ______ in order to replicate.

extra step

Viral Replication Steps (Diagram)

A viral envelope is a ______ coat made up of proteins and lipids.

non-rigid

The latent period is the time between ______ and ______.

infection, cell lysis

A nucleocapsid consists of ______ and the ______.

nucleic acid, capsid

What specimens can be collected for viral culture?

- Red top tube

- Swabs

- Fluid

- Tissue

- Stool

- Urine

- Aspirations

- Secretions

- Eye exudate

- Lesions, ulcers

Collection for viral culture should be done within the first ______ days of disease.

3

Transport for viral culture uses a buffered ______ solution.

isotonic

A ______ source and ______ can be able found within the transport container for viral culture specimens.

protein, antibiotics

The container for viral culture transport must be ______ and leak-proof.

sterile

The specimen must be ______ or frozen if delayed over 4 days (except CMV/RSV).

refrigerated

To diagnose acute measles, mumps or rubella, ______ or ______ should be performed.

RT-PCR, serology (IgM)

To diagnose convalescent measles, mumps or rubella, ______ should be performed.

serology (IgG)

EIA/ELISA is used to detect viral ______ or virus-specific ______ via an enzymatic color change.

antigens, antibodies

The ______ of the color created by EIA or ELISA correlated with the amount of target antigen/antibody present

intensity

Direct EIA detects viral ______, while indirect EIA detects viral ______.

antigen, antibody

Direct Immunofluorescence (DFA) detects viral ______ inside cells.

antigen

Indirect Immunofluorescence (IFA) detects viral ______.

antibodies (IgG and IgM)

What are the cell lines typically used to culture viruses?

Primary, diploid and continuous cell lines

Primary cell lines are derived directly from ______ and have a limited lifespan.

tissue

Diploid cell lines are normal human cells that divide a ______ number of times.

limited

Continuous cell lines are immortalized/tumor-derived and have ______ replication.

unlimited

What cell lines should be used to culture measles?

Continuous or primary

What cell lines should be used to culture mumps?

Primary or continuous

What cell lines should be used to culture rubella?

Diploid

Hemadsorption is used to detect viruses that express ______ on the surface of infected cells.

hemagglutinin proteins

Hemagglutinin proteins bind ______ to the infected cell surface.

RBCs

Hemadsorption involves the combination of ______ into viral cell culture.

washed RBCs

If the virus expresses hemagglutinin on the surface of the infected cells, the RBCs will ______ to the cell surfaces.

adhere (positive result)

Measles and mumps are hemadsorption ______, while rubella is hemadsorption ______.

positive, negative

The standard inoculation method involves the addition of sample directly to the ______.

culture medium

The adsorption inoculation method enhances viral infection by allowing the virus to ______ cell surfaces before adding media.

adhere to

The adsorption inoculation method mimics ______ more closely an dincreasees sensitivity.

natural infection

The shell vial method for viral isolation enhances viral _______ to cell monolayers using centrifugation.

adsorption

The shell vial method detects viral replication early by ______ for viral antigens instead of waiting to see the cytopathic effect.

immunofluorescent staining

Shell vial method procedure

- Coverslip with monolayer of cells is placed inside a shell vial

- Add the clinical specimen

- Centrifuge

- Incubate

- Use fluorescent microscopy to see positive (fluorescent) cells

Positive (fluorescent) cells indicate the presence of ______.

viral replication

What are some advantages of the shell vial culture over the standard vial culture?

- Faster

- More sensitive

- Less labor-intensive

The shell vial method is especially useful for ______ clinical diagnosis of viruses.

rapid