TCID50 Assay Concepts and Calculations

The video tutorial explains the TCID50 assay, a method for quantifying viruses that do not form plaques. It covers the protocol for performing the assay, including preparing serial dilutions and inoculating host cells. The video also details the calculation of TCID50, using proportionate distance and log dilution, and explains how to convert the result to PFU per mL.

What is the primary purpose of the TCID50 assay?

• To quantify viruses that form plaques

• To measure the size of viruses

• To determine the color of viruses

• To quantify viruses that do not form plaques

What is the significance of the '50' in TCID50?

• It shows 50% of the assay is complete

• It means 50% of the virus is inactive

• It indicates 50% of the cells are infected

• It represents 50% of the virus concentration

In the TCID50 assay protocol, what is the first step involving host cells?

• Incubate cells with virus

• Add virus directly to cells

• Plate cells in a 96-well plate

• Measure cell death

What is the purpose of making serial dilutions of the virus in the TCID50 assay?

• To change the virus type

• To ensure even distribution of the virus

• To decrease the virus concentration

• To increase the virus concentration

During the TCID50 assay, why is it important to resuspend the wells well before moving to the next dilution?

• To increase the temperature

• To decrease the pH level

• To change the color of the solution

• To ensure the virus is evenly distributed

What is the incubation condition for the cells after inoculation with the virus in the TCID50 assay?

• Room temperature with no CO2

• 50°C with CO2

• 37°C with CO2

• 25°C with no CO2

How is the proportionate distance (PD) calculated in the TCID50 assay?

• By subtracting 50% from the percentage above 50% and dividing by the difference between percentages above and below 50%

• By dividing the percentage above 50% by the percentage below 50%

• By subtracting the lower percentage from the higher percentage

• By adding the percentages above and below 50%

What is the log lower dilution in the TCID50 calculation?

• The dilution with no cell death

• The dilution just below 50% cell death

• The dilution just above 50% cell death

• The dilution where 100% cell death occurs

How is the TCID50 per ml calculated from the TCID50 value?

• By multiplying by the volume of virus added

• By dividing by the volume of virus added

• By adding the volume of virus added

• By subtracting the volume of virus added

What additional step is needed to convert TCID50 per ml to PFU per ml?

• Divide by 0.5

• Multiply by 0.69

• Divide by 0.69

• Multiply by 0.5