- Volume 44, Issue 3, 1979

Purified preparations of heracleum latent virus (HLV), which has very flexuous filamentous particles of about 730 × 12 nm, contain a single sedimenting component with s020,w = 96 S, A 260/A 280 = 1.50 and buoyant density in Cs2SO4 = 1.24 g/ml. The particles possess a single polypeptide, mol. wt. 23500, apparently lacking in tryptophan, and a single-stranded RNA of apparent mol. wt. 2.3 × 106 in nondenaturing conditions or 2.15 × 106 in denaturing conditions. The infectivity of the particles is sensitive to ribonuclease; this sensitivity is increased after exposure to EDTA, but is not decreased by addition of Mg2+ or Ca2+. HLV thus closely resembles apple chlorotic leaf spot virus, to which it is serologically unrelated; it is regarded as a tentative member of the closterovirus group. Its cryptogram is R/1:2.3/(5):E/E:S/Ve/Ap.

The sensitivity of interfering herpes simplex virus (HSV) particles to u.v.-irradiation was studied in a virus stock of HSV-1 strain ANG that contained an excess of interfering over infectious particles. Following u.v.-irradiation, samples of this virus stock were assayed for their plaque-forming capacity and their capacity to interfere with the replication of unirradiated standard virus. Depending on the assay conditions, interfering particles appeared to be less, equally, or more sensitive to u.v. light than infectious particles. It is concluded that interference is a gene function of interfering particles rather than being exerted directly by structural constituents of these particles.

A 29 nm non-cultivable virus (NCV) was detected in faecal extracts from children hospitalized for gastroenteritis. The NCV had a density of 1.35 g/ml in glycerol-potassium tartrate density gradients and was resistant to degradation by proteolytic enzymes, non-ionic detergents and pH extremes. The surface of these virus particles had knob-like projections which appeared to have a symmetrical arrangement. When heated to 56 °C, the virus was completely degraded to soluble components which could not be seen by electron microscopy.

Representative isolates of the paramyxoviruses duck/Hong Kong/75 and duck/Mississippi/75 were shown to be serologically closely related by haemagglutination and neuraminidase inhibition tests. The structural polypeptides of these viruses were also shown to be similar. For each of the isolates tested, polyacrylamide gel electrophoresis in the presence of SDS revealed a similar polypeptide pattern consisting, under reducing conditions, of seven polypeptides with apparent mol. wt. ranging from 46000 to 190000. Each virus had two glycosylated polypeptides with apparent mol. wt. of 56000 and 71000 to 72000 under reducing conditions and 62000 to 63000 and 135000 to 142000 under non-reducing conditions.

Linearized unit length DNA obtained after cleavage of the supercoiled DNA of the human papovavirus BKV by PstI (0.31) induced transformation and T antigen less efficiently than DNA cleaved by EcoRI (0.0), BamHI (0.98), KpnI (0.90) or HhaI (0.73). BKV DNA cleaved by XbaI (0.27 and 0.95) did not induce T antigen.

Treatment of Epstein-Barr virus-determined nuclear antigen (EBNA) with DNA resulted in blocking of its ability to convert acid-fixed EBNA-negative cell nuclei to an EBNA-positive form. Epstein-Barr virus (EBV) DNA, herpes simplex virus type 2 (HSV-2) DNA and DNA isolated from three lymphoblastoid cell lines differed in their potency to block this reaction. EBV DNA was found to be about three times more effective than cellular DNAs in abolishing the ability of DNA-cellulose-purified EBNA to convert acid-fixed nuclei to the EBNA-positive form; the effect of HSV-2 DNA was of intermediate character. No difference was found between the blocking potency of DNAs isolated from EBV-genome-negative Ramos cells and EBV-genome-positive Raji and P3HR-1 cells.

Particles of tobacco necrotic dwarf (TNDV) and potato leafroll (PLRV) viruses, both of which are phloem-limited and transmitted by aphids in the persistent manner, contain a single-stranded RNA of mol. wt. 2.0 × 106, estimated from their mobilities in polyacrylamide gel electrophoresis. The results suggest that both viruses belong to the group of luteoviruses. TNDV has two minor RNA components of mol. wt. approx. 1 × 105.