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At least 721 records · Page 40Linked to original sources
PubMed1989

Replication of Mayaro virus in Aedes albopictus cells: an electron microscopic study.

The replication of Mayaro virus in Aedes albopictus cells, was studied by electron microscopy at various times post-infection. In infected cells we observed the presence of cytoplasmic vesicles containing viral nucleocapsids and mature virus particles but at no time did we detect virus budding into such vacuoles. Budding of virus through plasma membrane was rarely observed. Our results are discussed considering the possibility of the release of virus particles to the extracellular space by exocytosis.

Aedes↗
PubMed1989

Replication of sialodacryoadenitis virus in mouse L-2 cells.

Sialodacryoadenitis (SDA) is a naturally-occurring infection of the laboratory rat raused by the coronavirus, sialodacryoadenitis virus (SDAV). The study of SDAV has been limited because there is no widely available continuous cell line for the propagation of high titers of the virus. The purpose of this study, therefore, was to compare the ability of SDAV to replicate in the permanent cell lines, LBC, of rat origin, and the mouse cell lines. L-929 and L-2. Following 2 to 6 repeated passages of SDAV in LBC cells, the virus could be readily propagated in LBC and L-2 cells, but not in L-929 cells. Similarly, SDAV adapted to replicate directly in L-2 cells could be readily propagated in LBC, but not L-929 cells. In LBC and L-2 cells, cytopathic effect (CPE), viral antigen, viral particles, and virus infectivity could be demonstrated. Titers of up to 10(8.0) infectious viral particles/0.25 ml of culture fluid were obtained at 48 hours in L-2 cells. Titers in LBC cells were one to two logs lower. When susceptible rats were inoculated with eighth passage L-2 cell-adapted virus, they developed typical lesions of SDA. Virus could be recovered from infected tissues and propagated in L-2 cells on first passage. The ability to propagate SDAV to high titers in the widely available L-2 cell line should promote the study of this virus and facilitate its comparison with other murine coronaviruses.

Animals↗
PubMed1975

Effect of alkaline maintenance medium upon the growth of rabies virus in chick embryo cells.

HEP Flury strain of rabies virus was propagated in chick embryo cells under maintenance media of different pH. It was found that viral growth was better and reached a markedly higher maximum titer when the initial pH of maintenance medium was 8.2 to 9.0 than when it was 7.4. The enhancement of viral growth was not ascribable to mere neutralization of acids produced from infected cells, because the different media became almost equally neutral within an early phase of growth curve. Serial passage of the virus in chick embryo cells using pH 8.2 maintenance medium resulted in altered growth characteristics of the progeny virus; first, the virus so passaged could now grow equally well under alkaline and neutral maintenance media, and, secondly, autointerference observable with the parent virus eventually lowered virus yield when neutral maintenance medium was used, but this effect of undiluted passage was eliminated by the use of pH 8.2 maintenance medium.

Animals↗
PubMed1975

Evidence of chronic persistent infections with polyomaviruses (BK type) in renal transplant recipients.

Ten renal transplant recipients showing a significant increase in human polyomavirus antibodies, indicative of an acute infection, were followed up serologically over periods ranging from two months to more than two years. Fifty-four serum specimens were available for the study and they were tested by both haemagglutination-inhibition and complement-fixation. Polyomavirus antigens were prepared from the BK and SV40-like strains of polyomaviruses, and from the SV40 virus. One strain of polyomavirus, related to the BK strain was isolated from the urine of one of these patients. Two other BK strains were recovered from the urine and kidney, respectively, of transplant recipients not included in this study. Sera of these two patients were not obtained until the transplantation was made; they were already highly positive for polyomavirus antibodies, precluding the demonstration of an increase in antibody titer. Serologic results have shown that HAI antibodies persist at high titers throughout the observation period. This persistence ranged from two to four months (four cases), seven to eleven months (three cases) and thirteen to twenty months (three cases). In none of the cases could a decrease of high titer be demonstrated. Moreover, density gradient studies have shown that specific IgM antibodies also tend to persist over many months. Similar serologic results were obtained in complement-fixation tests with a BK antigen. Titers were at least 1 in 30 in the study group, but were not observed among healthy blood donors. All sera were uniformly negative for SV40 and SV40-like antigens. One polyomavirus isolation was successful from urine obtained six months after initial serologic evidence for a polyomavirus infection. The other two viruses were isolated from materials taken four and seven months after first detection of polyomavirus antibodies at high titer. Both serologic evidence and viral isolations seem to indicate that polyomaviruses (BK type) might cause a chronic infection in humans.

Animals↗
PubMed1977

Serological relationships between rotaviruses from different species as studied by complement fixation and neutralization.

Human, piglet, mouse, foal, lamb, calf and rabbit rotaviruses all infected, but could not readily be subcultured in LLC MK2 cells. Cells infected with mouse and calf rotaviruses reacted by indirect immunofluorescence (FA) with convalescent serum from children, piglets, mice, foals, lambs, calves or rabbits, taken after rotavirus infection. Human, calf, piglet, mouse and foal rotaviruses reacted with human, calf, mouse, foal and lamb convalescent serum by complement fixation (CF). It was not possible to distinguish between different rotaviruses by CF or FA. Neutralization tests, however, detected species-specific rotavirus antigens. Any virus was neutralized by a much higher dilution of homologous species convalescent serum than by any heterologous serum. With the exception of the mouse virus there was very little cross reaction. However, in sera with a very high neutralizing titre for the homologous virus the titre was proportionately raised against heterologous virus. It is, therefore, now possible to type to species an unknown rotavirus by a neutralization test in LLC MK2 cells using convalescent serum from each species.

Animals↗
PubMed1989

Evaluation of continuous cell lines in antiviral studies with murine cytomegalovirus.

Cell culture systems were developed for rapid antiviral drug screening, using murine cytomegalovirus (MCMV) as an alternative to the slower growing human CMV. Since previous assay methods with MCMV employed mouse embryo fibroblasts (MEF cells), which are labor intensive to prepare and die off after 3-4 passages from primary culture, identification of virus-susceptible continuous cell lines was desirable. Three cell lines were found useful for assaying MCMV: C127I, SC-1, and 3T3. The antiviral agents acyclovir, ganciclovir, 5-fluoroarabinofuranosylcytosine, and 2'-fluoro-2'-deoxy-5-iodoarabinofuranosylcytosine were evaluated in the 3 continuous cell lines and in MEF cells. The 50% virus- or cell-inhibitory concentration values determined for each compound did not vary much from cell to cell. MEF cells were 10-fold more sensitive than the other cell lines to quantify virus from mouse organs, however. Virus propagated in 3T3 and SC-1 cells were as virulent to mice as salivary gland virus, whereas virus from MEF and C127I cells was more attenuated. Overall, C127I cells were judged to be the best for large scale antiviral screening in vitro, but MEF was the cell type of choice for titration of viruses from mouse organs and tissues.

Animals↗
PubMed1976

Development of a new human polyoma virus strain (MG).

A polyoma virus isolated from the urine of a renal transplant patient has been grown on primary human foetal fibroblasts and its pattern of replication studied by thin section electron microscopy. Virus replication is characterized by the appearance of spherical, crystalline arrays in the nucleoplasm which differ from the nuclear virus crystals found in cells infected by the human polyoma virus prototypes JC and BK. A serological study has substantiated differences between the prototypes and the MG isolate. The affinity of MG and other polyoma viruses for the cell membrane suggests a possible basis for the demyelinating effect seen in cases of polyoma-associated progressive multifocal leucoencephalopathy.

Antigens, Viral↗
PubMed1976

The use of chicken tracheal organ cultures for the isolation and assay of avian infectious bronchitis virus.

A study has been made of the use of chicken tracheal organ cultures for the isolation and assay of avian infectious bronchitis (AIB) virus from both naturally and experimentally infected chickens. Six strains of AIB virus were investigated, 3 of which had been isolated from natural outbreaks of disease. Two of the virus isolations from the outbreaks of AIB were made directly into tracheal organ cultures without passage in embryonated eggs. Organ cultures prepared from 20-day-old embryos were used since they were found to be somewhat more sensitive in virus assay than those derived from chickens of up to 31 days of age. Ciliostasis, which was used as the marker of infectivity, was complete by 3 days after inoculation with each strain of virus examined. Virus could be isolated from both respiratory and non-respiratory tissue in tracheal organ cultures and these cultures were found to be at least as sensitive as 9-day-old embryonated eggs in detecting AIB virus either in pathological material or in serial dilutions. When virus was assayed in both systems, the titres were very similar. It is considered, therefore, that chicken embryo tracheal organ cultures offer a reliable alternative system to embryonated eggs for studying AIB virus.

Animals↗
PubMed1977

Growth of Orungo virus in various tissue cultures.

Monolayer cultures of cell strains derived from Cercopithicus kidney (Vero), baby hamster kidney (BHK-21), duck embryo (DE), new-born rabbit kidney (MA-111), and Aedes albopictus were tested for their ability to support the growth of Orungo virus. The virus multiplied to high titres with accompanying cytopathic effect (CPE) in Vero and BHK-21 cultures, but not in the other three culture systems. The yield of virus from infected Vero cell cultures incubated at 37 degrees C was 30 to 100 times greater than in infected cultures incubated at 23 degrees C. In addition, a CPE was observed earlier and reached completion at the higher incubating temperature. Tiny plaques 1 to 2 mm in diameter were produced only in Vero but not in BHK-21, MA-111, DE or Aedes albopictus systems.

Aedes↗
PubMed1975

Experimental studies concerning the possibility of a latent carrier state in bovine herpes mammillitis (BHM).

Adult bovines, young calves and young rats were infected with bovine herpes mammillitis (BHM) virus providing a group of BHM-recovered animals in which to investigate a possible latent carrier state. The progression of the acute infection and serological response was essentially similar to that previously reported. The effect of natural (calving, littering) and artificial (corticosteroid treatment) stress on these animals following recovery from infection was investigated, but reactivation of BHM was never detected. Long term observation of cocultures of BHM virus infected-and-recovered bovine teat dermis with bovine embryo cells failed to reveal any evidence for the induction of BHM virus replication even in those cocultures treated with mitomycin C or bromodeoxyuridine. Similarly, cocultures utilizing lumbar dorsal root ganglia from the same animals were also negative with respect to the induction of virus replication. Experiments using cytosine arabinoside indicated that an artificial in vitro latent carrier state of BHM virus could be maintained for 6 days with subsequent sporadic virus reactivation, but an attempt to maintain such a state for 12 days was unsuccessful, with no subsequent virus reactivation.

Adrenal Cortex Hormones↗
PubMed1975

Exacerbation and reactivation of Herpesvirus hominis infection in mice by cyclophosphamide.

Cyclophosphamide has been shown to potentiate the growth of Herpesvirus hominis in the skin of Webster Schneider mice. Higher skin yields of virus were obtained, marked dissemination of virus to the brain was produced and mortality in mice was increased. Serum neutralizing antibody titres were suppressed. The system may serve as a good model for the study of specific antiherpes drugs.

Animals↗
PubMed1979

Isolation and cell culture propagation of rotaviruses from turkeys and chickens.

Rotaviruses were detected by electron microscopy in the faeces of turkey poults and broiler chickens with diarrhoea. Apparently symptomless infection was also observed in broilers. The avian rotaviruses could not be isolated in cell cultures by conventional techniques, but were adapted to serial growth in chick cell cultures following trypsin treatment of the virus and the cells. Immunofluorescence studies showed that the avian and mammalian rotaviruses are antigenically related. Antibodies to rotavirus were widespread in sera collected from turkeys, chickens and ducks.

Animals↗
PubMed1987

Maturation process of Japanese encephalitis virus in cultured mosquito cells in vitro and mouse brain cells in vivo.

The maturation process of Japanese encephalitis (JE) virus in C6/36 cells in vitro and in mouse brain cells in vivo was studied by electron microscopy. In the C6/36 cell infection, 500 to 2250 virions per cell were released into the medium during the period of study; yet, no virus budding process was observed at the host cell membranes. JE virions at various maturation stages appeared within the cisternae of rough endoplasmic reticulum (RER) of infected cells at 24 hours p.i.; and, although C6/36 cells did not show a well-developed Golgi apparatus, the virions appeared to be carried to the cell surface within host-cell secretory vesicles for extracellular release as early as 24 hours p.i. The occurrence of a secretory-type intracellular transport of maturing JE virus particles was well recognizable in brain cells of infected mice, in which JE virus particles were found almost exclusively in the cisternae of RER, in the Golgi apparatus, and in various vesicles, including coated vesicles, in the vicinity of the Golgi apparatus. Our previous study of dengue-2 virus morphogenesis and our present study of JE virus morphogenesis differed substantially at various stages of maturation. Possible mechanisms which explain these differences were discussed.

Animals↗