composed of a single strand of ribonucleic acid (RNA) and a single peptide of molecular weight 59,500, hereby designated protein N.

Three major and three minor structural proteins were identified by polyacrylamide gel electrophoresis of purified infectious virions of the Indiana serotype of vesicular stomatitis (VS) virus disrupted with acetic acid, 0.5 M urea, sodium dodecyl sulfate (SDS), and 2-mercaptoethanol. Molecular weights of the six virion proteins were estimated by comparative electrophoretic migration of known marker proteins in the presence of SDS. The following values were obtained: major proteins P6 _ 34,500, P5

Digitonin, a sterol glycoside which complexes with cholesterol, stripped off the envelope of vesicular stomatitis (VS) virions and liberated two viral structural proteins, 83% of P6 and 53% of P4. Deoxycholate also disrupted VS virions but released nucleocapsid cores which could be identified by higher buoyant density, ratio of incorporated 3H-uridine to "C-protein, and electron microscopy. The major nucleocapsid protein was P5 but varying amounts of the minor protein aggregate P2 were present, depending on the concentration of urea used for extraction. P2 appeared to be a polymer of P5. Two other minor structural proteins, P1 and P3, could not be located in the virion. From these data, we conclude that the three microscopically identifiable structures of VS virions are each composed primarily of a single major protein, as follows: P6 = envelope protein, P4 = protein of underlying "shell," and P5 = nucleocapsid protein.

No abstract

Fifty-seven hybridomas producing antibodies to tetanus toxoid or to the Ibc or B-IIb fragment of the toxin were isolated independently. Competitive inhibition studies demonstrated that monoclonal antibodies from mice immunized with the toxoid bound to at least 20 different epitopes on the toxoid molecule. Similar competitive binding studies revealed eight distinct epitopes on the B-IIb fragment and three to five epitopes on the Ibc fragment of the toxin. Neutralization of toxicity was effected by nine distinct monoclonal antibodies from hybridomas of toxoid-immunized mice and by one monoclonal antibody from BIIb-immunized mice. Mixtures of two, three, and four different monoclonal antibodies in a variety of combinations exerted a synergistic effect of ca. 200-fold over that observed with individual monoclonal antibodies, indicating that efficient neutralization may involve the simultaneous binding of at least two antibody molecules to different specific regions of the toxin molecule. Only one toxoid-induced monoclonal antibody failed to bind to tetanus toxin. All neutralizing antibodies bound to epitopes on the heavy chain of tetanus toxin. Six of these were directed toward epitopes on the NH2-terminal half, whereas four bound to epitopes on the carboxy-terminal half of the heavy chain. Only one monoclonal antibody bound preferentially to the light chain, but two other monoclonal antibodies appeared to bind to both chains, indicating some homology between these two chains.