Comparison of various methods for preparation of viral serological antigens from infected cell cultures

In efforts to prepare more potent and sensitive viral serological antigens, several aspects of the production of antigens from infected cell cultures were studied. Antigens derived from whole, infected culture material and from the cellular and fluid phases were compared. Freezing and thawing, sonication, and alkaline buffer extraction were compared for effectiveness in releasing antigen from host cells. The effect of the multiplicity of infection on titers of viral antigens produced in cell cultures was studied. Generally, higher titered antigens were derived from the infected cells than from the culture fluids, but for certain viruses complement-fixing (CF) antigens derived from the culture fluids gave higher antibody titers than did cell-associated antigens. With each virus-host cell system studied, treatment with alkaline buffers extracted appreciable amounts of CF antigen from the host cells, but in some instances more antigen was released by freezing and thawing or by sonication. Extraction of infected cells with alkaline buffers was not a satisfactory method for preparation of hemagglutinating (HA) antigens for any of the viruses studied. The highest-titered HA antigens were produced from infected cells disrupted by freezing and thawing or sonication. The highest titered CF and HA antigens were produced from cell cultures infected at multiplicities of one or greater. Complement-fixing antigens produced by infecting cells in suspension and then planting had lower titers than antigens produced in parallel by infecting developed monolayers. Optimal methods are summarized for preparation of serological antigens to a variety of viruses of man.