Abstract
The infectivity of polyoma virus may be assayed by measuring haemagglutinin induced in a single cycle of infection in mouse kidney cells by a method similar to that used for quantification of influenza virus (Cairns et al. 1952). Although less sensitive than plaque assay (Dulbecco & Freeman, 1959) or end-point titration (Rowe et al. 1959) the method is more rapid.
Primary mouse kidney cells (Nordenskjöld & Krakoff, 1968) were grown in Eagle's minimum essential medium in Earle's solution + 10% calf serum. For virus production the cells were grown in Roux bottles and for plaque assays in 60 mm. plastic Petri dishes (Falcon Plastics Inc.). The medium was changed daily for the first 3 days. The Glasgow variant of polyoma virus (Crawford, Crawford & Watson, 1962) was kindly provided by Dr G. di Mayorca, Naples.