FLK cell culture chronically producing bovine leukemia virus (BLV) and spontaneously contaminated with mycoplasma (M. sp.) was studied by electron microscopy. Information on the features of the ultrastructural organization of M. sp. and its direct relationships with BLV was obtained. BLV virions are capable of adsorbing on mycoplasma surface and penetrate inside, apparently in the course of phagocytosis. In the cytosole of M. sp. free-lying BLV virions devoid of the limiting membrane were found. In FLK cells both agents were regularly produced in high amounts causing no signs of death of the cell culture itself. From the foregoing, the FLK cells--BLV-M. sp. system appears to be quite balanced.

Animals↗

PubMedDate not supplied

[Behavior of Mycoplasma in a continuous cell culture of embryonic sheep kidney producing the bovine leukemia virus].

Mycoplasma sp. previously isolated from sheep embryo kidney cells producing bovine leukemia virus (FLK-BLV) was serologically identified in the growth inhibition test as M. arginini. SDS-PAGE of cellular proteins demonstrated their identity in M. sp. and M. arginini. Upon artificial inoculation of FLK cells, M. arginini persisted in the cells for a long time and was detectable in high titres by all the methods used. Other species of mycoplasma were isolated from the cells by microbiological method but were detectable by other methods in first passages only. The phenomenon of "disappearance" of mycoplasma was not associated with the toxic effect on them of the ingredients used in cell propagation and of cell metabolism products. It is assumed that sheep embryo cells, M. arginini, and bovine leukemia virus is a fortunate biological model of natural infection.

Animals↗

PubMedDate not supplied

[Persistence of Sindbis virus in cultures either non-producing or irregularly producing oncornavirus].

Persistence of Sindbis virus (SV) was studied for 9 months in two lines of mouse cell cultures (BALB/C) in one of which the genome of endogenous ecotropic oncornaviruses was repressed. The other lines was exogenously infected at the level of plimary culture with Rauscher leukemia virus (RLV) and SV and showed gradual inhibition of oncornavirus functions. The presence of oncornavirus type C was not the necessary condition for the development of persistent SV infection, however it influenced the character of persistence. In both systems, sequential loss of the hemagglutinating and interferon-inducing activities, then infectivity of SV (61--82 days), and persistence of the noninfectious antigen of the arbovirus for 9 months were observed. The differences consisted in the time of appearance of homologous interference to SV: in the presence of oncornavirus earlier (40 days), under conditions of repressed oncornavirus genome later (179 days). Electron microscopic examinations showed that in the system infected with RLV and SV there occurred in the course of persistence a sharp activation of phagosome-lysosome complex accompanied by incorporation into phagocytolysomes of numerous intact and partially destroyed virions of SV and RLV and their release from cell with cytoplasmic fragments. Possible mechanisms of inhibition of functions of the oncogenic and infectious viruses in the reported model of mixed chronic infection are discussed.

Animals↗

PubMedDate not supplied

[Sedimentation characteristics of the virions and subviral particles of influenza C viruses].

Investigation of sedimentation and some other properties of subviral particles and native virions of influenza C viruses was carried out in comparison with influenza A virions. Sedimentation rate of influenza C viruses was found to be 0.6 of that of influenza A viruses, the optical density peak coincided with the peaks of hemagglutinating and infectious activities of both influenza A and influenza C viruses. Studies with 4 influenza C virus strains isolated in different years revealed no differences in their sedimentation rates and the curve pattern. Electron microscopic, electrophoretic, and sedimentation analyses showed higher fragility of influenza C virions than those of influenza A virus, and their trend to self-disintegration. Our data showed significant differences in the effect of proteases on influenza A and C viruses. With due regard to these differences, we modified the method satisfactorily used for production of influenza A subviral particles. Some properties of subviral particles of influenza C virus were studied.

Animals↗

PubMedDate not supplied

Adherence to gastric epithelial cells induces expression of a Helicobacter pylori gene, iceA, that is associated with clinical outcome.

Most persons infected with Helicobacter pylori strains that produce vacuolating cytotoxin and possess cytotoxin-associated gene A (cagA) genotype nonetheless remain asymptomatic, suggesting that additional genes are important in virulence. We hypothesized that adherence to gastric epithelium provides stimuli that induce expression of some virulence genes. Our aims were to identify expression of H. pylori genes induced by adherence and to determine if such genes were correlated with peptic ulceration, mucosal interleukin-8 (IL-8) levels, and gastric inflammation. RNA was isolated from an ulcer-derived strain and a gastritis-derived strain that were exposed or not exposed to gastric epithelial cells. These RNAs were used for random arbitrarily primed reverse transcription polymerase chain reaction to identify newly expressed transcripts unique to the ulcer-derived strain following adherence. Clinical isolates of H. pylori were characterized for presence of the newly identified gene, and mucosal IL-8 and inflammation were examined in gastric biopsies from the source patients. A novel H. pylori gene, iceA (induced by contact with epithelium), was identified. DNA sequences revealed two families, iceA1 and iceA2. iceA1 strains were significantly associated with peptic ulceration and increased mucosal concentrations of IL-8. Both iceA1 and iceA2 were expressed in vivo by respective H. pylori strains in gastric biopsies. Adherence to gastric epithelial cells in vitro stimulates the transcription of iceA1, an H. pylori gene that is highly correlated with pathological outcome.

Amino Acid Sequence↗