Recombinant protein expression using the Baculovirus Expression Vector System (BEVS) is a powerful tool for the production of therapeutics, diagnostics, and reagents. To maximize efficiency of protein production, and thereby reduce costs, it is important to optimize the production parameters. A crucial step in optimization is determining the best multiplicity of infection (MOI) for the system in use. Factors that can affect the MOI include the recombinant baculovirus itself as well as cell line type and media composition. Typically the titer of a viral stock is determined in a standard manner, and then that titer is applied to each and every parameter tested; for instance, titering the virus on a Spodoptera cell line in a serum-containing media, and then using those data to determine the MOI used to infect Trichoplusia cells in a serum-free media formulation. The results may suggest that either the Trichoplusia cell line or the media formulation is inadequate for protein expression when, in fact, the MOI was incorrect for that particular combination…
Tag: <span>viral titer</span>
Variation of viral titre and recombinant product yields reported for the baculovirus expression vector system have been attributed to many specific infection variables. These include multiplicity of infection (MOI) and cell density at time of infection and time of harvest, as well as virus bank quality and efficiency. The MOI is defined as the number of plaque forming units (pfu) per cell that are added at the time of infection. Virus titre (pfu/ml) is determined by the plaque assay method. The MOI parameter is easily manipulated and may be important in optimising recombinant protein yields. Other sources of variation during both cell growth and viral infection phases may be responsible for the range of reported yields. Past studies in our laboratory compared the behaviour of cells infected with high and low MOI values, specifically regarding nutrient limitation and deprivation. In addition to these aspects, the quality of the virus bank may be an important factor which influences heterologous protein yields in the insect cell baculovirus system. Thus, production yields may be correlated to virus efficiency…