The interaction of a series of hybridoma IgGs with reovirus particles Demonstration that the core protein λ2 is exposed on the particle surface

We have recently described the isolation of 19 hybridoma cell lines that secrete IgGs directed against reovirus-coded proteins, and characterized their specificities as judged by their ability to precipitate virus-coded proteins from lysates of infected cells. We describe in this paper the characterization of these hybridoma-secreted IgGs by their ability to react with reovirus particles. IgGs directed against three reovirus proteins were able to neutralize infectivity, inhibit hemagglutination, and precipitate/aggregate reovirus particles: those directed against polypeptides σ1 and σ3, both components of the outer reovirus capsid shell, and those directed against polypeptide λ2, a component of reovirus cores. In addition, some, but not all, of the IgGs directed against polypeptides μ1/μ1C and μNS also precipitate/aggregate reovirus particles. The fact that IgGs directed against λ2 possess strong neutralizing, hemagglutination inhibiting, and virus precipitating activities suggests that the projections or spikes that are present on reovirus cores and that are composed primarily or exclusively of λ2 project through the outer capsid shell to the surface of reovirus particles. This conclusion was confirmed by the demonstration that polypeptide λ2 could be labeled by means of the lactoperoxidase-catalyzed radioiodination technique under conditions when only known components of the reovirus outer capsid shell became labeled.