GB1492930A - Virus growth - Google Patents

Abstract

1492930 Feline virus vaccines AFG (STALHAM) Ltd 31 Oct 1974 [31 Oct 1973] 50622/73 Heading A5B [Also in Division C6] Antigenic material effective against a virus disease in cats e.g. feline panleucopenia, feline rhinotracheitis and feline picornaviruses is prepared by obtaining feline lung tissue free from virus disease, preparing a cell strain of the feline lung tissue, forming a culture of the cell strain, a tissue free virus corresponding to the virus disease and a nutrient medium, and growing the culture, and either (a) inactivating the virus or (b) attenuating the virus by serial passage in the cell strain. A vaccine comprises the antigenic material in an administrable form. A feline lung tissue may be prepared under aseptic conditions, disaggregating the lung tissue either by mechanical means or with an enzyme and culturing or sub - culturing the disaggregated lung tissue by serial passages in a nutrient medium preferably until a cell strain is obtained being either a diploid or heteroploid cell strain which is free from extraneous virus. The disaggregation may be performed in a buffered salt solution containing trypsin to form a suspension of cells which is transferred to the nutrient medium where it is cultured at 35‹C to 40‹C. The culture may be formed either (a) by seeding the virus to a suspension of the cell strain in the nutrient medium or (b) by adding the virus to the cell strain in the form of a confluent monolayer with subsequent addition of the nutrient medium such as by allowing the virus to adsorb on to the cells which are maintained at 20‹C to 40‹C preferably for 30 to 120 minutes is allowed for adsorption after which a quantity of the nutrient medium at a rate of 10 to 50 ml of the medium for every million viable cells and the whole is incubated at 30‹ to 40‹C desirably until a cytopathic effect takes place on the cells and wherein the culture is harvested when the cytopathic effect is near to completion e.g. when it has attained from 80% to 100%. After harvesting the cells and the liquid medium are separated by centrifuging and the liquid medium containing the extracellular virus is collected, the cells being then broken down for liberation of the cell associated virus. The cells may be treated by repeated freezing and thawing followed by separation of antigenic material from the cell debris by centrifugation. The nutrient medium may be Eagles Basal Medium maintained at a pH of 7.0 to 7.4 by the use of a buffering agent and containing calf serum or calf foetal serum.