Different sensitivities of Vero cells from two sources to avian reoviruses

A risk-assessment model to rate the occurrence and relevance of adventitious agents in the production of influenza vaccines

Influenza vaccine production has traditionally relied on the use of embryonated chicken eggs for virus isolation and propagation, but recently, cell-culture-derived manufacturing methods have been introduced. During influenza vaccine production, by either conventional or cell culture methods, there is a risk of incidental contamination by adventitious agents. Thus, a risk-assessment model has been developed to qualitatively assess the potential risk of vaccine process contamination by viral pathogens. The model takes into account the basic growth characteristics of each virus, its ability to grow in different cell substrates and resistance to processing steps during vaccine manufacture. The risk-assessment model has been applied to various pathogens to determine potential risk and relevance in different manufacturing scenarios, using different cell substrates for virus propagation, including Madin–Darby canine kidney (MDCK) cells. Avian viruses, introduced via use of embryonated eggs for virus isolation, were found to present the greatest risk, irrespective of the substrate used for influenza virus propagation. The use of MDCK cells to propagate vaccine virus from egg-isolated influenza virus strains does not introduce a new or greater adventitious virus risk, compared with egg-based vaccine production. Indeed, the adventitious virus risk is potentially reduced as fewer viruses are able to grow in MDCK cells.

Susceptibility of cell lines to avian viruses

The susceptibility of the five cell lines - IB-RS-2, RK-13, Vero, BHK-21, CER - to reovirus S1133 and infectious bursal disease virus (IBDV vaccine GBV-8 strain) was studied to better define satisfactory and sensitive cell culture systems. Cultures were compared for presence of CPE, virus titers and detection of viral RNA. CPE and viral RNA were detected in CER and BHK-21 cells after reovirus inoculation and in RK-13 cell line after IBDV inoculation and with high virus titers. Virus replication by production of low virus titers occurred in IB-RS-2 and Vero cells with reovirus and in BHK-21 cell line with IBDV.

Comparison of eight different procedures for harvesting avian reoviruses grown in Vero cells

14 avian reovirus isolates adapted to replicate in an African green monkey (Vero) cell line were studied for the nature of their replication. The growth curves of 5 viruses showed them to be highly cell-associated in Vero cells. Different procedures were examined for releasing the cell-associated virus following propagation in Vero cells, including several freeze-thaw cycles, treatment with sterile distilled deionized water (ddH2O), freon extraction, and trypsin treatment. Treatment of virus infected cultures with ddH2O was the most effective, and trypsin treatment was the least effective procedure for dissociation of virus from cells. Treatment of virus infected cultures with ddH2O is a simple and effective procedure which can be used where large amounts of virus are required for experimental purposes.