SUMMARYThe physicochernical and serological properties of a virus isolated from the bivalve mollusc, Tellina tenuis, have been examined. The virus has a diam. of 59 nrn, sediments at 43oS in sucrose gradients and bands at a density of I-32 g/ml in CsC1. The virus contains RNA with a tool. wt. about 2.8 × IO 6 as estimated by polyacrylamide gel electrophoresis but in sucrose gradients the RNA sediments at I4S. The virus RNA is resistant to ribonuclease under conditions in which ribosomal RNA and the single stranded Mengo virus RNA are completely hydrolysed. Two major polypeptides, mol. wt. 67 and 40 × Io z, and one minor polypeptide, mol. wt. I I0 × 10 8, are present in the virus particle. These properties are similar to those found for different serotypes of infectious pancreatic necrosis (IPN) virus. Although there was only a very low level of cross-neutralization between Tellina virus and IPN virus, there was some cross-reaction in immune electron microscopy tests and in irnmunofluorescence tests with infected tissue culture cells. This cross reaction, together with the close similarity in morphology and physicochernical properties, suggests that Tellina virus and IPN virus belong to the same virus group.

Methods were developed for the purification, at high yield, of four different particle types of African horsesickness virus serotype 9 (AHSV-9). These products included virus particles purified on CsC1 gradients which contain proteins apparently directly comparable to those ofbluetongue virus (VP1 to VP7); virus particles purified on sucrose gradients which also contain, as a variable component, protein NS2; infectious subviral particles (ISVPs), containing chymotrypsin cleavage products of VP2; and cores, obtained by treating purified ISVPs with 1 M-MgCIz to remove the components of the outer capsid layer (VP5 and VP2 cleavage products). Additional protein bands migrating with apparent Mrs lower than that of VP5 were detected during SDS-PAGE analysis of virus particles. These appear to be conform-

SUMMARYTrypsin (o.Img./ml.) reduced the infectivity of vesicular stomatitis virus by 5 log. within 5 miD. 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 [l~C]amino acids, but not from virus labelled with 3~p.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 5o% of radioactivity from virus labelled with asp 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.

SUMMARYTreatment of the infective component of vesicular stomatitis virus with Nonidet P4o produces an infective skeleton-like structure which has the shape and approximate size of the intact virus particle. The infectivity of the skeleton is enhanced I oo to I ooo fold by mixing with DEAE-dextran. The skeleton lacks the outer envelope and fringe structure and in consequence does not produce neutralizing antibodies in guinea pigs. The density of the skeleton is 1.22 g./ml, in potassium tartrate gradients compared with x "t4 g./ml, for the virus. Sodium deoxycholate removes protein from the skeleton and releases the filamentous ribonucleoprotein in an infective form. As with the skeleton, the infectivity of the ribonucleoprotein is enhanced by DEAEdextran. Ribonuclease has no effect on the ribonucleoprotein but trypsin destroys its infectivity. The ribonucleoprotein has a density of ~-22 g./ml, in tartrate gradients, sediments at about ~40 s in sucrose gradients and does not produce neutralizing antibodies in guinea-pigs.

Vesicular stomatitis virus contains single-stranded ribonucleic acid of molecular weight 3.6 X 106 and three major proteins with molecular weights of 75 x 103, 57 x 108, and 32.5 X 103. The proteins have been shown to be subunits of the surface projections, ribonucleoprotein, and matrix protein, respectively. From these values and from estimates of the proportions of the individual proteins, it has been calculated that the virus has approximately 500 surface projections, 1,100 protein units on the ribonucleoprotein strand, and 1,600 matrix protein units. Possible models of the virus are proposed in which the proteins are interrelated.