5
99.33
%
0.67
%
5
99.33
%
0.67
%
The MOI Calculator computes the Multiplicity of Infection, which is the ratio of infectious virus particles to target cells. MOI is a critical parameter in virology, gene therapy, and any experiment involving viral transduction or infection. Understanding MOI helps you control infection efficiency and predict what fraction of cells will be infected.
The calculator also uses Poisson distribution to estimate the probability that a cell will be infected by at least one virus particle.
MOI is defined as:
MOI = Number of Virus Particles / Number of Cells
The probability of infection follows a Poisson distribution. The fraction of cells infected by at least one virus is:
P(infection) = 1 − e^(−MOI)
At MOI = 1, approximately 63.2% of cells are infected. At MOI = 3, about 95% are infected. At MOI = 5, approximately 99.3% are infected.
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Using 5×10⁶ PFU to infect 1×10⁶ cells gives an MOI of 5, ensuring that 99.3% of cells receive at least one viral particle.
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An MOI of 0.1 means only about 9.5% of cells are infected, with most receiving a single virus. This is used when you want to ensure single-copy integration.
It depends on the application. For complete transduction of a cell population, MOI of 5-10 is typical. For single-copy gene delivery (e.g., lentiviral library screens), use MOI of 0.1-0.3 to minimize multiple integrations. For viral propagation studies, start with MOI of 0.01-0.1. Always optimize MOI empirically for your specific virus-cell system.
Virus-cell interactions follow a Poisson distribution, meaning viral particles distribute randomly among cells. At MOI = 1, some cells receive 0 particles, some receive 1, and some receive 2 or more. Mathematically, e⁻¹ ≈ 36.8% of cells receive no virus at all. This is why higher MOIs are needed for complete infection.
Use plaque-forming units (PFU), transducing units (TU), or infectious units (IU) rather than total physical particles, as not all particles are infectious. The MOI should reflect infectious particles only. Viral titers from plaque assays or functional transduction assays give the most relevant numbers.
Roboculator Team
The Roboculator Team explains calculations, planning tools, and practical formulas in clear language for real-life situations.
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