Recovery of soluble feline oncornavirus-associated cell membrane antigen from large volumes of tissue culture fluids.

Feline oncornavirus-associated cell membrane antigen (FOCMA), which is released spontaneously in tissue culture, was harvested from large volumes of culture fluid. Continuous-flow molecular filtration was the method of choice for concentrating the component. The yield of antigen recovered, as determined by cytotoxicity inhibition, was equal to that recovered with concentration in cellulose membrane tubing against polyethylene glycol and half that obtained by lyophilization. The latter two techniques were found to be impractical for handling large volumes of material. However, lyophilization was used for the final concentration step following volume reduction to approximately 300 ml in the molecular filtration system. Antigen yields were equivalent when removing salt by constant-volume molecular washing, prior to concentration in the filtration system, or when removing salt by conventional diffusion through cellulose membrane tubing.