- Volume 47, Issue 1, 1980

The early cell surface antigen (ECSA) induced by vaccinia or cowpox virus infection was analysed by immunoprecipitation and SDS-polyacrylamide gel electrophoresis (SDS-PAGE). The components with a mol. wt. of about 40000 (40 K) in vaccinia virus-infected cells and with a mol. wt. of about 43000 (43 K) in cowpox virus-infected cells were specifically immunoprecipitated with anti-ECSA serum prepared by immunizing rabbits with rabbit kidney cells infected with a conditional lethal mutant. The 40 K and 43 K polypeptides were synthesized even in the presence of cytosine-1-β-d-arabinofuranosyl-HCl (Ara C) and were detectable even in the cells pulse-labelled between 1 and 2 h p.i.

Trypsin treatment of varicella-zoster virus infected cells resulted in release of infective cell free virus in the supernatant. Varicella-zoster virus DNA could be isolated from purified virus. The DNA was infective and the mol. wt. was approx. 80 × 106 as determined by length measurements.

The characteristics of the virion-associated RNA-dependent DNA polymerase (RDPase) of a baboon endogenous virus, M7, were studied extensively; the optimal conditions for the exogenous RDPase reaction were obtained with 0.4 mm-Mn2+, 110 mm-NaCl, 24µg/ml poly(rA).oligo(dT)12–18, at pH 7.6 in the presence of 0.01% Brij-58. Under these conditions, the incorporation of 3H-TMP proceeded up to 90 min at a speed of 0.1 pmol TMP/µg virus protein/min. Poly(rC).oligo (dG)12–18 and poly(rCm).oligo (dG)12–18 served as the template-primers in the exogenous reaction with 3 mm-Mg2+ and 0.4 mm-Mn2+, respectively. Polyuridylic acid, bleomycin, rifampicin, spermidine and inorganic phosphate significantly inhibited the RDPase activity of BaEV. The RDPase of BaEV requires a higher concentration of NaCl, a lower pH and milder conditions of detergent treatment than those of other mammalian retroviruses.

A procedure is described for purifying the b1, b2 and b3 proteins from leaves of Nicotiana tabacum cv. Xanthi-nc, a cultivar reacting hypersensitively to tobacco mosaic virus (TMV). All three proteins consist of a single polypeptide, have similar mol. wt. of about 14200 but differ in charge. In contrast, the b4 protein differs from b1 to b3 in both charge and size. The same procedure purifies the proteins IV, III and II from TMV-infected leaves of N. tabacum cv. Samsun NN. The Samsun NN proteins IV to II resemble the b1 to b3 proteins from Xanthi-nc in electrophoretic mobility in polyacrylamide gels and in mol. wt.; b1, IV and III have similar amino acid compositions.

It is suggested that these proteins be called pathogenesis-related proteins (PRs) and a unified system of nomenclature is proposed which groups similar proteins.

In attempts to infect cucumber protoplasts with cucumber mosaic virus (CMV) RNA, the use of polyethylene glycol as an uptake inducer proved successful. This method involves resuspending protoplasts in high concentrations of polyethylene glycol in the presence of RNA, followed by rapid dilution. Levels of infection obtained with CMV-RNA were more reproducible than those using virus nucleoprotein. This method was also suitable for the inoculation of protoplasts with tobacco ringspot virus RNA.

In immunosorbent electron microscopy tests, large numbers of particles of a Scottish isolate of potato leafroll virus (PLRV) became attached to grids coated with antisera prepared to Canadian, Japanese or Swiss isolates of PLRV. Moderate numbers of particles became attached using antiserum to tobacco necrotic dwarf virus or to bean leafroll virus, smaller numbers using antiserum to soybean dwarf virus or to barley yellow dwarf virus (RPV strain) and a few particles became attached using antiserum to barley yellow dwarf virus (MAV strain) or to beet western yellows virus. A similar pattern of antigenic relationships was deduced from tests in which the binding of antibody molecules to PLRV particles exposed to different concentrations of the antisera was assessed by electron microscopy. It is concluded that these viruses should all be included in the luteovirus group and that their apparent degree of relationship to PLRV is: tobacco necrotic dwarf virus > bean leafroll virus > soybean dwarf virus > barley yellow dwarf virus (RPV strain) > barley yellow dwarf virus (MAV strain).