The use of proteolytic enzymes for harvesting insect cell lines which support nuclear polyhedrosis virus replication

Abstract

Various physical and enzymatic methods for harvesting insect cell lines, which grow as attached monolayers and which support the replication of nuclear polyhedrosis viruses (NPV), were investigated. Only 70 to 90% of cells were intact in cell suspensions produced by scraping and, on sub‐culture, the cells exhibited a lag phase of 1 to 2 days before growth resumed. An entirely satisfactory method for harvesting Spodoptera frugiperda cells using proteolytic enzymes could not be found. In contrast, trypsin or pronase could be used with Spodoptera littoralis cells. However, dispase, a neutral protease, proved to be the most effective enzyme giving 95 to 100% intact cells and, on sub‐culture, no inhibition of cell growth rate. Cells harvested using this gentle method are better for producing actively dividing low‐density cell monolayers which are needed for assaying and studying NPV.