Kinetics of influenza virus fusion with the endosomal and plasma membranes of cultured cells. Effect of temperature.

We performed a detailed kinetic analysis of influenza virus fusion with the endosomal and plasma membranes of Madin Darby canine kidney (MDCK) cells and provided a comparison of the kinetic parameters obtained for both cases at 20 degrees C and 37 degrees C. Using our mass action kinetic model, we determined that the fusion rate constant, f, for influenza virus with the endosomal membrane was 0.02 s(-1) at 37 degrees C and 0.0035 s(-1) at 20 degrees C. The analysis of the fusion kinetics of influenza virus with the plasma membrane yielded that the fusion rate constants were close to those deduced with the endosomal membrane. The systematic kinetic analysis performed in this study provides for the first time a biophysical support for studies on influenza virus-cell fusion where the acidic endosomal internal environment is simulated artificially by lowering the pH of the medium.