Patent ID: 7349812

Claim:
A method for determining the titer (concentration of virus or viral or non-viral vector particles) of a virus or viral or non-viral vector which interacts with living target cells and produces a product P, comprising: (a 1 ) incubating a virus or a viral or non-viral vector at an unknown initial concentration C with living target cells at constant initial concentration D, for a time and under conditions suitable for interaction of said virus or viral or non-viral vector with the living cells, and for the production of product P, wherein measurement of a parameter of product P which reflects the response of the living target cells to the virus or viral or non-viral vector particles provides a measurable signal, (b 1 ) measuring at various successive times t the intensity i of the signal produced by the interaction of said virus or viral or non-viral vector and said target cells, (c 1 ) determining β, the value of i at the inflexion point of the i=f(t) curve for the virus or viral or non-viral vector, (c 2 ) determining the time t β corresponding to the i=β value, chosen in the interval β min <β<β max , wherein β min and β max , respectively correspond to the values of i at the inflexion point of the i=f(t) curve for the minimal and maximal concentrations of a standard virus or viral or non-viral vector, for which the t β =f(C) curve is pre established, and (d 1 ) determining the initial concentration C of the virus or viral or non-viral vector using a t β =f(C) standard curve.