Asked 28th Jan, 2016

How to calculate the Multiplicity of infection (MOI)?

I have to do transduction using lentivirus and I have a doubt how to calculate the MOI. I have 5x10 3 ( 5000 viral particles/ ul). How much do I have to take to get MOI of 1 if I plate 10000 cells in a 12 well plate. 
I would also like to know if these cells are enough or would be too much for 50% confluency
Thanks in advance

Most recent answer

24th Aug, 2021
Wang Qianwen
Dankook University
MOI(Multiplicity of infection) means the ratio of phage particles and bcaterial cells.
MOI=phage particles/ bcaterial cells

All Answers (15)

29th Jan, 2016
Tom Masi
The University of Tennessee Medical Center at Knoxville
Hi Jaya,
An MOI of 1 is equal number of cells and virus particles. So in your case you would use 2ul of virus for 10,000 cells. An MOI of 2 would be twice the number of virus particles compared to cells.
It is difficult to answer your second question since you do not mention the cell type you are infecting. Different cell types require different MOIs to achieve a particular transduction efficiency. You should check the literature to see what MOIs people use.
Good Luck!
9 Recommendations
Dear Jaya,
MOI is related to pfu by the following formula:
Multiplicity of infection (moi) = Plaque forming units (pfu) of virus used for infection / number of cells.
For example, if 2x106 cells is infected by 50 ml of virus with a titer of 108 pfu/ml. The moi will be 0.05*108/2*106 = 2.5
See more in the attached 
6 Recommendations
31st Jan, 2016
Jaya Aseervatham
University of Texas Medical School
Thank you all for the reply
18th Jul, 2018
Sintayehu Fekadu
Hawassa University
Hello dear Jaya,
Regarding MOI, you can calculate simply making equal ratio of virus particle to cells to be infected. In this typical question, the titre of your virus is 5000 particles/ul, where as you are trying to infect with 10, 000 cells. So according to your virus titre and MOI of 1, you will use 2ul of the virus solution.
Regarding the 50% confluency of cells on 12 well plate, I suggest that you should check microscopy.
2 Recommendations
18th Jul, 2018
Jaya Aseervatham
University of Texas Medical School
Thank you. I will
23rd Jul, 2018
Oliver Thompson
Utrecht University
MOI x total amount of cells
____________________________ = volume seed virus (mL)
Titre seed virus (CCID50/mL)
5 Recommendations
18th Sep, 2018
Yara Sadek
Ulm University
How could I calculate the amount of bacteria to be added from thr resuspended bacteria to achieve a certain MOI ? does it depend on the cells seeded ? how come since the cells seeded are now confulent and way more ? I seeded 4000 and want an MOI of 250
4 Recommendations
12th Mar, 2019
Naveen Chaudhary
Postgraduate Institute of Medical Education and Research
MOI =ratio of phage to bacterial cells.phage concentration can be measured by double soft agar method and bacterial concentration by diltution method ,simple.
5th Jun, 2019
Naveen Chaudhary
Postgraduate Institute of Medical Education and Research
MOI=1 means f you have 1000 phage particles and 1000 bacterial cells.
Phage con. you can estimate by double layer soft agar method and bacterial load can beestimated by mishra dilution method.
MOI=0.1 means if you have 100 phage particles and 1000 bcaterial cells.
1 Recommendation
5th Jan, 2021
Mukesh Kumar
Institute of Genomics and Integrative Biology
The Multiplicity of infection (MOI):
1 cell = 1 virus: means MOI =1.
For your 10000 cells considering MOI =1,
you have 5000 viral particles in 1 uL,
10000 cells = 5000 x 2 uL (i.e. 10000 viral particle means MOI =1)
3 Recommendations
14th Feb, 2021
Aly fahmy Mohamed
it is a ratio of virus titer (TCID50) divided by cell No
10^6 = 1000000 virus
CElls = 1000 000
Ratio = 1000000/1000000= 1
So MOI = 1
1 Recommendation

Similar questions and discussions

How do I determine Optimal Multiplicity of Infection (MOI) of my phage isolates?
10 answers
  • Hasina MkwataHasina Mkwata
I have come across a protocol that I find helpful and would like to adapt. In this protocol, S.aureus cells are to be grown to their early logarithmic phase (OD600=0.5) and then infected with phage by using different MOI ratios (MOI= 0.01, 0.1, 1, 10, 100). After incubation at 37oC for up to 3.5 hours, the phage lysates are to be centrifuged at 10,000 x g for 3min and then filtered through a 0.22 μm pore size syringe filter and assayed to determine the phage titer.
Based on this protocol, my challenges are:
1.     How do I dilute the phage lysate to obtain the stated MOI ratios (0.01, 0.1, 1, 10, 100)? I have seen a general protocol for determining MOI ratios in Adenovirus where MOI ratios were calculated using a formula No. of cells *desired MOI=total PFU needed. Then use the formula: (total PFU needed)/ (PFU/ml) = Total ml of virus needed to reach your desired dose. Can I use this approach to determine the previously stated MOI ratios of my phage isolates?
2.     How do I scale up this protocol? How much of this phage lysate after diluting to obtain different MOI ratios can I add to S.aureus bacteria culture  to initiate infection/lysis? Or What appropriate volume of both diluted phage lysate and host bacteria can I work with?
3.     From the protocol, it is not stated if the cultures were incubated under shaking conditions. Is shaking of the cultures necessary during MOI determination?
Your Kind advice is highly appreciated. Thanks

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