Surface Structure of Vesicular Stomatitis Virus

Trypsin (0.1 mg./ml.) reduced the infectivity of vesicular stomatitis virus by 5 log. within 5 min. and destroyed immunizing activity. It also destroyed the complement-fixing activity against antiserum to the virus but the activity against antiserum to host cells was unaffected. The external spike-like projections of the virus were removed without affecting the remainder of the surface structure. Trypsin removed radioactivity from virus labelled with [14C]amino acids, but not from virus labelled with 32P.

Phospholipase reduced the infectivity to a much smaller extent than trypsin and the immunizing activity was apparently unaffected. After treatment with phospholipase, complement-fixing activity against antiserum to virus was also unaffected but the complement-fixing activity against antiserum to host cells was greatly reduced. Electron microscopy showed that the spike structure of the virus was unaffected by phospholipase C but the remainder of the surface was digested. The enzyme removed more than 50% of radioactivity from virus labelled with 32P in the phospholipid component. The results showed that the spike-like structure of the virus responsible for producing neutralizing antibodies is composed entirely of virus protein and the phospholipid component derived from the cells is located in the regions between the spikes. The spikes may be attached directly to the internal helical structure of the virus.