Monitoring of Host-Cell Infection and Virus-Induced Apoptosis in Influenza Vaccine Production

Abstract

Detailed knowledge of status and progress of host-cell infection in cell culture-derived vaccine manufacturing can be of great value for process design and optimization. Therefore, cell populations in a 5 L microcarrier system using adherent MDCK cells were monitored by flow cytometry for degree of infection and induction of apoptosis. Cells attached to microcarriers as well as detached cells were analyzed. About 8 h post infection the concentration of cells in the supernatant increased, followed by an increase in HA titers 2 h later. About 30 h post infection most cells had detached from the microcarriers and were apoptotic, while the virus particle concentration (HA) did not increase further. Virus yields mainly depended on the total number of adherent cells, and a high concentration of detached cells clearly indicated the end of the productive phase of cultivations. Therefore, measures to delay cell detachment, i.e. virus-induced apoptosis, could lead to higher virus titers in influenza vaccine production processes.