# Multiplicity of Infection - (Sep/09/2010 )

Hi

Can anybody explain how to calculate the MOI for cell lines?

-rimal-

I'm assuming you mean you will be infecting them with something?

MOI is the number of infectious particles per cell.

So, do a viable cell count and then add the appropriate amount of infectious agent for your desired MOI.

For example, you have 5x 10^5 cells, so for an MOI of 1, you add 5x 10^5 infectious agent......

-leelee-

I guess he wants to know the number of infectious particles per ml. I had some protocol for it some time ago... essentially, you use a serial dilution of your virus concentrate, put them onto a defined number of cells and quantify the percentage of infected cells. Then there was a formula, how to calculate that...
I will see if I find it again.

rsm

-Rsm-

I was really confused with this as well. The MOI is usually btwn .1 and 1.0. The MOI you choose is determined by how fast the virus grows. If I remember correctly, it's: for a higher titer virus, you would use a low MOI, for a low titer virus you would use a higher MOI. This prevents the cells from being wiped out so quickly.

Hope this helps.

-cmccray-

Hola, To me, Leelee, has a correct opinion. Rsm defines the titer or number of infectious particles /volume. And to clarify to Chccray, knowing the titer you could infect at low Multiplicity (MOI)0.1-0.5-1, or at high MOI 1-5-10. The difference is for what you want infect. If you infect at low MOI only a low part of the cells are infected, the virus repliques, infects more cells and at the end you have high concentration of virus in the medium (High titer passage). With this high titer passage you infect cells at high MOI (more viruses than cells), each cells is infected for some viruses, died and produces the protein coded in the viruses. Good day to everyone

-protolder-

protolder on Mon Feb 14 07:00:04 2011 said:

Hola, To me, Leelee, has a correct opinion. Rsm defines the titer or number of infectious particles /volume. And to clarify to Chccray, knowing the titer you could infect at low Multiplicity (MOI)0.1-0.5-1, or at high MOI 1-5-10. The difference is for what you want infect. If you infect at low MOI only a low part of the cells are infected, the virus repliques, infects more cells and at the end you have high concentration of virus in the medium (High titer passage). With this high titer passage you infect cells at high MOI (more viruses than cells), each cells is infected for some viruses, died and produces the protein coded in the viruses. Good day to everyone

Hi,

Another important aspect when deciding between low or high MOI infection is: (1) low MOI infection allows new infections to occur throughout the experiment, since not all cells were infected in the first time, and is good to evaluate virus dissemination; (2) on the contrary, high MOI infection permits just one cycle of virus growth, since all cells will be infected in the first time. You should decide based the objectives of your experiment.
Best,
Jonas

-jonas albarnaz-