Virus Cultivation and Assays

These flashcards cover key topics related to virus cultivation, assays, and the significant historical discoveries in virology as discussed in the lecture.

What method was routine for propagating the polio virus before cell culture?

Scientists infected non-human primates, paralyzed them, and removed their brains to make virus stocks.

In what decade was it discovered that many viruses could be propagated in embryonated chicken eggs?

The 1930s.

Where is the influenza virus primarily grown for vaccine production?

In chicken eggs.

Who made the discovery that poliovirus could multiply in human cell cultures?

John Enders, Thomas Weller, and Frederick Robbins in 1949.

What is a major characteristic of primary cultures derived from animal tissues?

They have a limited time span of no more than 5 to 20 cell divisions.

What are continuous cell lines, and why are they not used for vaccine production?

Continuous cell lines can be propagated indefinitely but are not used for vaccines because they can be tumorigenic.

What type of culture allows for the growth of cells in suspension?

Spinner or Suspension cultures.

What is a cytopathic effect (CPE)?

Visible changes in cells that occur when viruses infect them, observable under a microscope.

What does a plaque assay measure in virology?

used to measure number of infectious virus particle in a sample by counting the plaques formed on a cell layer.

What is the significance of the one-step growth cycle in studying viruses?

It allows researchers to study virus reproduction in a synchronized manner following infection.

What percentage of physical virus particles are infectious particles in a sample?

The Particle/PFU ratio quantifies the number of infectious versus non-infectious particles.

What is the purpose of the hemagglutination assay in virology?

To identify influenza viruses based on their ability to agglutinate red blood cells.

What is the role of reverse transcriptase in measuring viral enzyme activity?

It catalyzes the conversion of RNA into DNA, which can be quantified in laboratory tests.

What do phylogenetic trees measure?

The genetic distance between organisms and identify their nearest relatives.

What were the first viruses identified through unbiased sequencing in patients with pneumonia in Wuhan, China?

A previously unknown betacoronavirus named 2019-nCoV.

why do CPE’s matter

clear sign of viral infectivity so scientists use it to identify and measure virus activity

are all virus particles infectious and what is the term for measuring this 

no not all particles are infectious  some are defective, term for measuring is particle/pfu ratio 

what is dose-response curve used for

used to study how virus concentration affects the number of plaques formed in plaque assay

what makes one-hit kinetics

only one infectious virus particle is needed, it has a linear graph shape, and number. of plaques increases directly with virus concentration

what makes two-hit kinetics

has 2 virus particles to infect cell together, forms a parabolic graph, the number of plaques increases with the square of the virus concentration 

endpoint dilution assay

estimates how much infectious virus is in a sample, looks for the lowest concentration of virus that can still infect cells

steps for one-step growth cycle

take bacteria and add bacteriophage

adsorb

dilute culture

incubate

sample at different times

plaque assay

hemaggluntination assay

detects virus that bind and clump red blood cells, quick 30 min, ex:influenza

ELISA ( enzyme-linked immunosorbent assay

uses antibodies to detect viral proteins (antigens) or antibodies against a virus in a sample and quantify their presence based on color change. ex: nasal washes, blood, or sereum

eclipse period in one step animal viruses

phase in which infectivity is lost when virions are disassembled after penetrating the cells- no viruses

latent period in one-step animal viruses

time it takes to replicate, assemble, and release new virus particles before lysis 

multiplicity of infection

number of infectious particles added per cell , moi= number of virus particles / number of target cells