摘要:

Studies are reported of persistent simian virus 40 (SV40) infections of fully permissive monkey (TC-7 and BSC-1) and human (A172) cell lines, with emphasis on the role of viral defectives in establishment and maintenance of persistence. The presence of defectives prevented complete cell killing and allowed the establishment of persistently infected cultures. Hirt supernate DNAs from these cultures showed the continuing presence of defective genomes. Restriction enzyme analysis demonstrated that altered defective genomes evolved during passage of the carrier cultures, but that they always reflected structures of the genomes used to establish the cultures. There was some host cell specificity in the effectiveness of establishment of persistence, e.g., TC-7-derived defectives were more effective in preventing killing of TC-7 than of BSC-1 or A172 cells. Persistent infections of TC-7 cells could also be established in the absence of defectives, but in the presence of neutralizing anti-SV40 antiserum. In fact, defectives were eliminated from carrier cultures established in the presence of antiserum. When antiserum was withdrawn, the wild-type SV40 grew and destroyed the cells. Antiserum maintains a low level of infection by neutralizing viruses outside the cells, so that many cells do not become infected. Defectives are eliminated because spread of infection is effectively at very low multiplicity. Carrier cultures that are established and maintained by defectives result from intracellular interference by the defectives with the normal development of wild-type virus.

ISSN:0300-5526    

DOI:10.1159/000149359

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Human skin fibroblasts were previously shown to be resistant to coxsackie B4 virus infection. We have cultured fibroblasts from skin and lung tissues of donors of various ages. By a novel method for direct assay of virus adsorption and penetration, we have shown that skin fibroblasts from young fetuses are susceptible to coxsackie B4 infection, whereas those from older fetuses, children and adults are not and that this refractoriness is caused by a tissue-specific block to virus penetration.

ISSN:0300-5526    

DOI:10.1159/000149360

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Ether extracts of 495 Chinese medicinal herbs from 106 families were studied for Epstein-Barr virus (EBV) early antigen (EA) induction in the Raji cell system. 15 herbs from 10 families were found to have inducing activity. Water extracts of the same herbs also had inducing activity, but it was not as strong. The significance of these herbs in the activation of EBV in vivo and their relation to the development of nasopharyngeal carcinoma are discussed. No EA-inducing activity was found in 73 samples of 14 different foods tested.

ISSN:0300-5526    

DOI:10.1159/000149361

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Examination of newborn mice, inoculated intraperitoneally with high doses of scrapie virus, revealed that the virus could not be reisolated from their tissues after about 1 week following inoculation, until almost 1 year later. The inoculum was rapidly removed and was not detectable, although the animals became latently infected. Homogenization of whole inoculated newborn animals showed that only about 3% of virus could be recovered by the 2nd day postinoculation (p.i.). During the first 6 days p.i. the half-life of titratable scrapie was about 15 h. A further study of the rate of disappearance of clarified scrapie virus from blood after intravenous inoculation showed an even more rapid disappearance, with a half-life of 5.16 min. Prior treatment of the recipient mice with either carbon black or silica to block the reticuloendothehal system (RES) did not affect the rate of disappearance. It was concluded that the mouse possesses a very efficient means of scrapie virus removal from the blood which is not dependent upon an active RES. However, after 1 h the rate of disappearance changed dramatically; the residual virus level was very stable, with no significant drop during the next 21 h. This finding was compatible with the possibility that two forms of scrapie virus, with different removal rates, coexisted in the inoculum. Silica treatment caused a shortened scrapie incubation period.

ISSN:0300-5526    

DOI:10.1159/000149362

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

We compared some of the biological and structural features of an adenovirus type 2 temperature-sensitive mutant (tsl) defective for maturation cleavages and uncoating with wild-type (WT) virus. The cleavage defect caused tsl to produce virions at 39° that contained five precursor proteins (pTP, UK, PVI, PVΠ, PVIII). Coinfection of cells with such tsl virions and a variety of mutants or WT virus not only failed to complement tsl but actually depressed the infection by the second virus. The uncoating defect could only be overcome by multiplicity-dependent leakiness. The structure of the tsl virion was compared with that of WT virus by iodination with chloramine-T, chloroglycoluril and lactoperoxidase, by cross-linking, and by digestion with proteases. Aside from the presence of precursor proteins and the greater stability of tsl virions, no other differences were found that could account for the uncoating defect. Therefore, we postulate that this defect was caused by the greater stability imparted to the virion by precursor proteins PVI, PVΠ and PVI

ISSN:0300-5526    

DOI:10.1159/000149363

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The murine cell surface receptor for Rauscher murine leukemia virus was analyzed using a binding assay involving cultured murine cells and 125I-labeled envelope glycoprotein, gp70, of the virus. The binding was competitively inhibited by extracts of ecotropic murine viruses. No inhibition was observed with a xenotropic or an amphotropic murine type-C virus, a murine type-B virus, and several nonmurine retroviruses. Unlike cells producing ecotropic murine viruses, murine cell lines actively producing either an endogenous xenotropic virus or an amphotropic virus showed a significant degree of receptor activity for Rauscher murine leukemia virus gp70. When murine cells were induced with iododeoxyuridine to produce a xenotropic virus and an ecotropic virus in distinct phases, the receptor activity of the induced cells remained unchanged during xenotropic virus release, but a dramatic decrease was evident with the onset of ecotropic virus release. These findings show that ecotropic murine viruses share a common receptor on the murine cell surface and that this receptor is distinct from those for xenotropic and amphotropic murine viruses.

ISSN:0300-5526    

DOI:10.1159/000149364

出版商:S. Karger AG    

年代:1983

数据来源: Karger

ISSN:0300-5526    

DOI:10.1159/000149365

出版商:S. Karger AG    

年代:1983

数据来源: Karger

ISSN:0300-5526    

DOI:10.1159/000149366

出版商:S. Karger AG    

年代:1983

数据来源: Karger

ISSN:0300-5526    

DOI:10.1159/000149358

出版商:S. Karger AG    

年代:1983

数据来源: Karger