- Volume 19, Issue 2, 1973

The species specificity of chick and L cell interferons were studied with respect to uptake and activity in mouse and chick embryo cell cultures. Heterologous interferons conditioned cells for the rapid uptake and accelerated development of the antiviral state for homologous interferons. Heterologous interferons were neither taken up nor antiviral, regardless of whether the cells were conditioned with homologous or heterologous interferons.

Measles virus was grown in HEp-2 cells and purified by sedimentation on potassium tartrate gradients. The virus formed a sharp band at a density of 1.23 (g/cm3). Treatment with sodium deoxycholate disrupted measles virus particles, releasing virus nucleocapsids which sedimented at approximately 280 S and were resistant to pancreatic ribonuclease. Equilibrium density sedimentation of nucleocapsids in CsCl gave a visible band at a density of 1.30 (g/cm3). The E 280/E 260 ratio of dissociated nucleocapsids was 0.88, consistent with an RNA content of 5.0%. RNA extracted from purified virus and nucleocapsid had a sedimentation coefficient of 52 to 54 S in sucrose density gradients and a mol. wt. of 6.4 × 106 when fractionated on polyacrylamide-agarose gels. The polypeptides of purified virus and nucleocapsid were separated by polyacrylamide gel electrophoresis. The intact virus particles contained six polypeptides of mol. wts. 75600, 69000, 60000, 53000, 51000 and 45700. The nucleocapsid contained a single polypeptide of mol. wt. 6 × 104.

When potato virus X (PVX) is exposed to enzymically oxidizing chlorogenic acid, and re-isolated, some of its properties are changed. Its u.v. spectrum is modified and centrifuged pellets are coloured: its u.v. fluorescence is diminished, a longer-wave fluorescence is introduced: it produces less colour with 2,4,6-trinitrobenzene sulphonic acid, and moves faster during electrophoresis. There is, however, little or no loss of infectivity in the course of the reaction. The results suggest that PVX combines with chlorogenoquinone to produce a modified but infective virus (PVX-Q) and it is thought that this reaction may occur naturally.

The polypeptides synthesized in L cells infected with vaccinia virus have been examined using the technique of labelling with [35S]-methionine followed by polyacrylamide gel electrophoresis. Virus-specific polypeptides were detectable as early as 20 min after infection. The polypeptides have been classified on the basis of the sensitivity of their synthesis to inhibitors of RNA and DNA synthesis. The mode of regulation of early vaccinia virus protein synthesis is discussed.

The structural antigen Band II was present in cells infected with either type 1 or type 2 herpes simplex virus. Antiserum to Band II neutralized the infectivity of both virus types. General antisera to either type exhibited type specific neutralizing activity after absorption with heterologous antigen. Absorption of the antisera with Band II antigen from cells infected with either type 1 or type 2 virus also abolished the type common but not the type specific neutralizing activity. Fractions obtained by preparative polyacrylamide gel electrophoresis have been examined in serum blocking tests. The results suggest that particles of herpes simplex virus possess at least two type specific antigens and one type common antigen (Band II); interaction of any of these with the corresponding antibody causes loss of virus infectivity.

A line of White Leghorn fowl (line 151) was found to be segregating for susceptibility and resistance to RSV(RAV-O), an avian tumour virus belonging to subgroup E. Family mating within the line, and test matings with other inbred lines, were made to determine the mode of inheritance of susceptibility. The results were fully consistent with the two loci hypothesis advanced previously for control of response to RSV(RAV-O), and not with a single locus hypothesis.

The protein and nucleic acid components of elderberry latent virus (ELV) were of similar size to those of tomato bushy stunt virus (TBSV) when examined by electrophoresis in polyacrylamide gels. Estimates of the mol. wts. of the proteins were 40000 (ELV) and 42000 (TBSV), and the estimates of the mol. wts. of the nucleic acids were 1.55 × 106 (ELV), and 1.8 × 106 (TBSV). Buoyant densities in caesium chloride were 1.363 g/cm3 (ELV) and 1.348 g/cm3 (TBSV). To account for differences in sedimentation coefficient and in buoyant density between ELV and TBSV, and in comparison with the structure of 180 + 12 protein subunits proposed for TBSV, we suggest that the most likely number of protein subunits in particles of ELV is 120.

A comparison was made of the two RNA species of the CAM isolate of tobacco rattle virus. The RNAs were found to have significantly different base compositions. Double-stranded virus-specific RNA was extracted from virus infected tissue and was used with [3H]-labelled virus RNA in hybridization experiments. Hybridization competition experiments showed that most sequences in each RNA species were unique to that species, but that a sequence of about 500 nucleotides may be common to both.

Acid–base titrations of cowpea chlorotic mottle virus and its protein suggest that when the virus changes from the compact pH 6.0, 88 S form to the ‘swollen’ pH 7.0, 78 S form a series of changes in the dissociation constants of several amino acid residues is initiated. One such change probably occurs slowly and involves several basic amino acids and this is used to explain the hysteresis observed between acidic and basic titrations. Homoconjugate hydrogen-bonded carboxylic acid groups are probably involved in the swelling process and at least one of these on each sub-unit is detected by displacement of its single associated proton with magnesium. If magnesium is present, the hysteresis between acidic and basic titrations is not found. These observations are discussed in terms of the reversible configurational change undergone by the virus. Electrophoretic data suggest that the ratio of basic to acidic amino acids is greater on the surfaces of the protein subunits buried in the capsid rather than on the surface exposed externally on the capsid.