The Infectious Cycle and Viral Diagnostics

Question 1

What is virus reproduction?

Answer 1

The sum total of all events that occur during the infectious cycle

Question 2

What is the one-step growth curve?

Answer 2

A single reproduction cycle that occurs synchronously in every infected cell

Question 3

What is a susceptible cell?

Answer 3

A cell that provides the receptors required for virus entry

Has a functional receptor for a given virus

Question 4

What is a permissive cell?

Answer 4

A cell that is able to support virus reproduction when viral nucleic acid is introduced

Virus can be reproduced in a permissive cell

Question 5

What is a monolayer?

Answer 5

A layer of cultured cells growing in a cell culture dish

Question 6

What are primary-cell cultures?

Answer 6

Cell cultures prepared from animal tissues

These cultures include several cell types and have a limited life span usually no more than 5 to 20 cell divisions

Question 7

What are continuous cell-lines?

Answer 7

Cultures of a single cell type that can be propagated indefinitely in culture

Question 8

What are cytopathic effects?

Answer 8

The morphological changes induced in cells by viral infection

Question 9

What is a virus titer?

Answer 9

The concentration of a virus in a sample

Question 10

What are plaque-forming units (PFU) per milliliter?

Answer 10

A measure of virus infectivity

Question 11

What is hemagglutination?

Answer 11

The linking of multiple red blood cells by virus particles resulting in a lattice basis of method to measure virus concentration

Question 12

What is the eclipse period?

Answer 12

phase in which infectivity is lost when virions are disassembled after penetrating cells

Question 13

What is the latent perioid?

Answer 13

how long it takes virus to get out of the cells once it is made

Question 14

What is the multiplicity of infection?

Answer 14

number of infectious particles ADDED per cell

Formula:
MOI = Amount of virus (PFU) / # of cells

Question 15

What are the 5 key steps to the viral infectious cycle ?

Answer 15

1. Attachment and entry
2. Translation
3. Genome replication
4. Assembly
5. Release

Photo on chapter 3

Question 16

What are two conditions that need to be satisfied to have a successful viral reproduction?

Answer 16

The cell HAS to be susceptible and permissive

Question 17

What is the ONLY cell in which a virus can enter and be reproduced?

Answer 17

A susceptible and permissive cell

Question 18

Are the infectious cycle and virus reproduction synonymous?

Answer 18

Yes (synonymous = same)

Question 19

How do you know a cell has been infected with virus?

Answer 19

If they are susceptible and permissive, they will likely show CYTOPATHIC EFFECTS

Though, not ever cell will show cytopathic effects

Question 20

What is a syncytia?

Answer 20

Large multinucleate cells

Multiple cell fusions of uninuclear cells

Question 21

How is syncytia formed?

Answer 21

Syncytium formation is induced by viral infection

Question 22

What are some virus examples of syncytia?

Answer 22

Herpesvirus
Paramyxovirus
Poxvirus
Reovirus
Retrovirus

Question 23

What is the American Type Culture Collection (ATCC)?

Answer 23

A nonprofit organization

Established in 1925

Collects, stores, and distributes materials for R&D. These reference microorganisms and cell lines of any tissues.

Distributes to >150 countries

Question 24

What is an organoid?

Answer 24

3D structures derived from STEM CELLS that maintain identity of organ being studied

An advancement in cell culture

Question 25

What can organoids be used for? (applications)

Answer 25

``` Disease mechanism Toxicology Development and stem cell biology Regenerative medicine Drug discovery Infectious disease ```

Question 26

What are the differences between bacterial and viral reproduction?

Answer 26

Bacterial reproduction has an exponential growth Viral reproduction has a eclipse period and a burst period

Question 27

What is a burst period?

Answer 27

One virus yields multiple viruses

Question 28

What is a intracellular?

Answer 28

Infectious virus found WITHIN cells

Question 29

What is a extracellular?

Answer 29

Infectious virus found within the SUPERNATANT of cells

Question 30

How do scientists cultivate (grow) viruses?

Answer 30

Cell culture Laboratory animals Embryonated eggs

Question 31

What cytopathic effects would be visible by conventional light microscopy?

Answer 31

Rounding up and detachment of cells from culture dish Cell lysis Welling of nuclei Syncytium formation

Question 32

On average, how long does it take to make a vaccine in chicken eggs?

Answer 32

6 months

Question 33

Who was Henrietta Lacks and why was she significant?

Answer 33

An African American woman who died in the early 1950s from cancer and whose cells provided the world's first and still widely used continuous cell lines

Question 34

What vaccine was tested in HeLa cells by Jonas Salk in the 1950s?

Answer 34

Polio

Question 35

What is plaque assay?

Answer 35

Determines virus titer, the concentration of virus in sample

Question 36

Where and when was plaque assay modified?

Answer 36

Modified in 1952 by Renato Dulbecco in animal virology

Question 37

What technique is used for plaque assay?

Answer 37

The monolayer of cultured cells + virus with the addition of nutrient medium + supplement agar will result in plaque formation.

Question 38

Describe plaque formation

Answer 38

Circular zone of infected cells Dyes may enhance contrast

Question 39

How is the virus titer from a plaque assay measured?

Answer 39

Measured in plaque forming units (PFU) / mL 10x fold dilutions 0.1mL aliquots of virus inoculated onto susceptible cells

Question 40

What is the formula for determining virus titer?

Answer 40

(plaque count)(virus dilution)(10)

Question 41

What is the distribution of virus particles per cell in MOI?

Answer 41

Poisson Distribution (bell shaped curve) P(k) = e^-mm^k/k P(k) = fraction of cells infected by k virus particles e^-m = 1/e^m

Question 42

What is the starting RTPCR covid test material?

Answer 42

RNA because covid-19 is a RNA virus

Question 43

What does IgM show?

Answer 43

IgM shows early infection

Question 44

What does IgG show?

Answer 44

IgG shows long term infection | things you've have and past through, etc

Question 45

What are biological ways to detect viruses?

Answer 45

Plaque Assay

Question 46

What are physical ways to detect viruses?

Answer 46

Hemagglutination Imaging virus particles - Electron Microscopy - Live-cell imaging of fluorescent virions Serology - Immune components in the blood - ELISA Nucleic Acids - PCR, RTPCR, deep sequencing

Question 47

What are the protein components of the immune system?

Answer 47

2 light chains, 2 heavy chains

Question 48

What are antibodies made of?

Answer 48

Made by B cells

Question 49

What are the 5 types of antibodies that circulate in the blood?

Answer 49

IgA, IgD, IgE, IgG, and IgM

Question 50

What do antibodies do?

Answer 50

Recognizes antigens and neutralizes them

Question 51

What is an antigen?

Answer 51

any foreign substance (virus, bacteria, sometimes your own body (autoimmunity))

Question 52

What does enzyme-linked immunosorbent assay (ELISA) detect?

Answer 52

With a second antibody and a captured antibody, detects viral proteins in sample With anti-IgG, detect antibodies in sample

Question 53

What is lateral flow immunochromatographic assay?

Answer 53

Modification of ELISA Used in rapid antigen detection test kits - Pregnancy: human chorionic gonadotropin (HCG) - Sample: urine or blood

Question 54

What are the steps in COVID-19 rapid serology antibody test of the lateral flow immunochromatographic assay?

Answer 54

1. Sample loading 2. Buffer loading 3. Sample incubation 4. Antibody-antigen recognition 5. COVID-19 antibody detection 6. Control antibody detection 7. Interpreting results

Question 55

What is the RT-PCR princple?

Answer 55

1. Denaturation 2. Primer annealing 3. Extension

Question 56

What is the threshold line in RT-PCR?

Answer 56

reaction reaches fluorescent intensity above background levels

Question 57

What is the copy threshold (Ct)/copy quantification (Cq) value?

Answer 57

PCR cycle number where sample reaction curve intersects threshold line

Question 58

What is environmental/deep sequencing?

Answer 58

Simultaneous sequencing of thousands to millions of DNA molecules

Question 59

What are applications of deep sequencing?

Answer 59

Virus discovery Genome organization Evolution (phylogenetic relationships)