Mar 19, 2025
Calculating Multiplicity of Infection (MOI)
- Briana McGovern1,2,
- Kris White1,2
- 1Icahn School of Medicine at Mount Sinai;
- 2ASAP Discovery Consortium
- ASAP Discovery
Protocol Citation: Briana McGovern, Kris White 2025. Calculating Multiplicity of Infection (MOI). protocols.io https://dx.doi.org/10.17504/protocols.io.rm7vzj1wrlx1/v1
License: This is an open access protocol distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited
Protocol status: Working
We use this protocol and it's working
Created: August 07, 2024
Last Modified: March 19, 2025
Protocol Integer ID: 104826
Keywords: MOI, infection, antiviral, analysis, ideal moi for antiviral screening, multiplicity of infection, calculating multiplicity, ratio of viral particle, multiplicity, ideal mois, antiviral screening, viral particle, mois, infection, amount of cell, virus
Funders Acknowledgements:
National Institutes of Health/National Institute Of Allergy and Infectious Diseases (NIH/NIAID)
Grant ID: U19AI171399
Abstract
Multiplicity of infection (MOI) is the ratio of viral particles to cells. The ideal MOI for antiviral screenings will depend on several things - the cell type, the cell passage, the virus type, the amount of cells, etc.
Troubleshooting
Before start
The appropriate MOI for antiviral screenings will depend on several factors - the cell type, the cell passage, the amount of cells, the virus type, etc.
We always run an MOI test, which is an MOI dilution series, when we create fresh cell or virus stocks. From this MOI test we select the MOI that achieves approximately 30% infectivity.
Virus Dilution Calculator (1).xlsx10KB Use this excel sheet for quick MOI dilution calculation.
Or if you would prefer to perform by hand:
1. desired MOI x (# cells / well) = Plaque Forming Units (PFU)/well
2. (PFU/well) x (1000/50) = PFU/ml needed
3. (stock titer) / (PFU/ml needed) = Dilution Factor
4. ((5ml x # plates)(1000)) / DF = total volume of virus stock needed
5. (5ml) - (volume of virus stock) = amount of 2% media for the dilution
For example,
our current stock of SARS-CoV-2 WA1 has a titer of 3.5e6 PFU/ml
we want to infect the wells with MOI 0.05
we have 5 plates and we want to infect wells with 50ul volume (~estimate 5ml volume needed per plate)
0.05 (1.6e4 cells/well) = 800 PFU/well
800 (1000/50) = 16,000 PFU/ml
(3.5e6)/16,000= 218.75
((1000(5ml x 5 plates)) / 218.75 = 114.29 ul SARS-CoV-2 WA1 virus stock needed
5ml - 114.29ul = 4,885.7 ul 2% Media