Studies of mitochondria and mitochondrial DNA extracted from organelles harboring an intramitochondrial virus

(1) Two viper cells lines were investigated, one which harbors IMV in the mitochondria (VSW cells) and one without detectable IMV (VH3 cells). (2) The size of closed circular mtDNA molecules from both VSW and VH3 cells was found to be significantly greater (5.4 to 5.6 micron) than the contour lengths of typical mammalian cells (4.8 to 5.2 micron). (3) A small percentage of mini-circles ranging in size from 0.1 to 0.6 micron was observed to band with closed circular mtDNA from both cell lines. Minicircles were especially abundant in VH3 cells. (4) MtDNA from VSW cells contained 34.1% dimers plus oligomers (10.2% oligomers), whereas VH3 cells had only 14.8% dimeric and oligomeric forms (5.4% oligomers). (5) Treatment of VSW cells with 1 microng/ml ethidium bromide for 48 hours resulted in an increased incidence of IMV (IMV in 15% of mitochondrial sections) as compared with untreated VSW cells (IMV in 3% of mitochondrial sections).

Failure to SV40-transformed lizard cells to induce tumors in autogeneic or allogeneic hosts

Lizard cells from the tails of geckos were readily morphologically and antigenically transformed in vitro by SV40 virus. Neither autografts of these cells nor allografts of SV40 transformed gecko embryo cells produced tumors in animals under observation for 1 to 3 years.

Ocular pathology induced by the suckling mouse cataract agent

The eye disease caused by SMCA may be best characterized as an endophthalmitis, with early retinitis followed by subsequent posterior uveitis. Pathologic features of lens included: proliferation and abnormal posterior extension of lens epithelium, increased accumulation of lens capsule material, and production of aberrant lens substance. Cataractous change appears to be secondary to intraocular inflammation. In addition to the above pattern, in roughly 20 per cent of all cases, 3 weeks after inoculation, lens capsule is destroyed giving rise to a foreign body granulomatous reaction.

Thermal inactivation of rabies and other rhabdoviruses: stabilization by the chelating agent ethylenediaminetetraacetic acid at physiological temperatures

Thermal inactivation of rabies and several other rhabdoviruses was studied using virus suspended in several different diluents. Rabies serogroup viruses were more stable than Kern Canyon or vesicular stomatitis viruses. Limited studies of two fish rhabdoviruses requiring low temperatures (less than 33 C) for replication indicated that they were not markedly more thermolabile than rabies virus. Bovine serum protein components in complex cell culture media stabilized virus at 56 C, but at temperatures of less than or equal to 37 C, sodium tris (hydroxymethyl)-aminomethane (NT) buffer containing ethylenediaminetetraacetic acid (EDTA) (NTE) was a much more efficient stabilizer of virus infectivity. Chelating agents EDTA and ethyleneglycol-bis-(beta-aminoethyl ether)tetraacetic acid were equally efficient in protection of rabies virus infectivity; the effect of each was lost when excess Ca2+ was added. Bovine serum in NT or NTE buffers produced a thermostabilizing effect at 37 C not provided by the same serum concentration in complex cell culture media. Bovine serum was more efficient than EDTA in stabilizing virus infectivity during repeated cycles of freezing and thawing.

Temperature-sensitive mutants of rabies virus in mice: a mutant (ts2) revertant mixture selectively pathogenic by the peripheral route of inoculation

Analysis of the pathogenic potential in mice of a variety of rabies and rabies serogroup viruses revealed that an apparently revertant population of virus derived from CVS mutant ts 2 had a unique capacity to selectively induce paralytic disease when given by a peripheral [intraplantar (i.pl.)] route of inoculation. Little paralytic disease was induced by high concentrations of virus administered by the intracerebral (i.c.) route, whereas paralytic disease and death were characteristically induced in mice given only a few infectious doses of virus i.c. Disease induced by i.pl. inoculation was dose dependent. Mice frequently survived paralytic disease induced by i. pl. inoculation, with clinical signs often persisting indefinitely; mice surviving i.c. inoculation of high concentrations of virus frequently exhibited chronic nonspecific signs of minor debility. Analysis of the ts 2 virus population indicated that it was composed of a mixture of ts and revertant virions, each with characteristic pathogenic (or nonpatholgnic) propensities, none of which was identical to the original composite ts 2 virus populations. Despite the heterogeneity of the ts 2 virus population, the typical pathogenic pattern of selective pathogenic capicity after i. pl. inoculation at high doses was retained during 11 ocnsecutive passages in suckling mouse brain. ts 2 virus was demonstrated to interfere with the disease-producing capacity of CVS fixed rabies virus when ts 2-CVS mixtures were inoculated i.c. However, attempts to demonstrate a particular propensity for induction in vitro of "autointerference" by ts 2 in serial passage in BHK-21 cell culture inoculated at high multiplicity were unsuccessful.

Structural and enzymatic characterization of viper C-type virus

The structural polypeptides of purified viper range in molecular weight from 11,000 to 97,000 daltons and consist of 3 major and about 13 minor polypeptides. The virus contains both protein kinase and reverse transcriptase activities. Several of the structural polypeptides are phosphorylated in vitro by the virus-associated protein kinase. However, most (possibly all) of the viral structural polypeptides are not phosphorylated in vivo. DeoxyATP is as efficient as ATP in donating phosphate for in vitro phosphorylation of viral proteins. In vitro protein phosphorylation always precedes transcription and the virus-associated protein kinase and reverse transcriptase activities can be partially separated by sedimentation in a sucrose gradient.

An ultrastructural study and model of membrane-intramitochondrial virus relationships

Intramitochondrial virions (IMV), in many respects structurally similar to 'C-type' viruses of higher organisms, are synthesized in close topographical association with inner mitochondrial membranes of the viper spleen cell line, VSW. Cristal membranes contribute to the formation of a trilaminar viral envelope, whereas the outer mitochondrial membrane does not appear to play any structural role in virion maturation. Two schematic models, correlated with electron microscopic images, are presented to depict: (a) the relative location of the particles within a three-dimensional view of the mitochondrion, and (b) the sequence of virion-mitochondrial membrane relationships during morphogenesis.

Cell to cell transmission of virus in the central nervous system. II. Experimental rabies in mouse

Rabies virus replication in suckling and adult mouse brains inoculated with either fixed or street virus was studied by light and electron microscopy. Chronologic study of fixed virus-infected suckling mice showed that virus budded from the plasma membrane of neuronal cell processes and perikarya prior to the development of intracytoplasmic virus particles. Nucleocapsids and virions were observed exclusively in perikarya and cellular processes of neuronal cells and, on rare exception in an astrocyte indicating high neurotropism of rabies virus regardless of the strain of virus and the age of host animal. Virus transit between contiguous neuronal cell processes and perikarya was observed in suckling and adult mouse brain after both street virus and fixed virus infection. Nucleocapsids and virions were also found in myelinated axons in addition to the unmyelinated neuronal cell processes. The implication of cell to cell spread of virus within the central nervous system in rabies virus infection is discussed.

Host effect on vesicular stomatitis virus morphogenesis and "T" particle formation in reptilian, avian, and mammalian cell lines

The morphogenesis of vesicular stomatitis virus (VSV) in three reptilian cell lines (turtle heart, gecko lung, and viper spleen) was studied by thin section electron microscopy. Simultaneous growth studies were conducted in reptilian, chick embryo fibroblast, and BHK/21 cells to compare the yields of infectious VSV during serial passages. The mean length of gecko lung cell VSV measured from electron micrographs is statistically significantly shorter than that of VSV replicating in other reptilian systems studied. This observation, along with comparative growth studies, suggests the predilection of gecko lung cells to form "auto-interfering" truncated "T" rather than infectious "B" VS virions.

Maturation of rabies virus by budding from neuronal cell membrane in suckling mouse brain

Two strains of tissue culture-grown rabies virus developed in suckling mouse brain predominantly by the process of virus budding from the neuronal cell membrane.

RNA polymerase associated with virions of pike fry rhabdovirus

The association of an RNA-dependent RNA polymerase activity with virions of pike fry rhabdovirus has been demonstrated by both in vitro and in vivo studies. The temperature optimum for the in vitro assay is around 20 C, although enzyme activity can be observed at 4 C. Preparations of pike fry virus possess a glycoprotein, a membrane protein, a nucleoprotein, an L protein, and a phosphoprotein, as well as an RNA of about 3.8 times 10-6 mol wt. A protein kinase activity has been found associated with virus preparations. In vitro RNA product analyses indicate that the virus-associated enzyme functions principally as a transcriptase synthesizing viral-complementary, heteropolymeric RNA.

Fish rhabdovirus replication in non-piscine cell culture: new system for the study of rhabdovirus-cell interaction in which the virus and cell have different temperature optima

The replication of three rhabdoviruses associated with diseases of fish has been demonstrated in cells of continuously cultivated non-piscine cell lines. Spring viremia of carp (SVC) virus and the salmonid fish viruses, Egtved and infectious hematopoietic necrosis virus, all replicated in mammalian WI-38 (human diploid cell strain) and BHK/21 cells and in cells of one or more reptilian cell lines at the temperatures commonly used to propagate these viruses in fish cells. The infections were cytopathic: SVC virus plaque assays may be performed in several types of mammalian cell culture. "Autointerference" apparently mediated by abortive "T" particle formation was observed during serial nondiluted passages of SVC virus in BHK/21 and TH1 cells, but not in RTG-2 or WI-38 cells. Optimal temperatures for replication of SVC and Egtved viruses in BHK/21 cells were identical to those determined in poikilothermic vertebrate cell cultures. However, these viruses replicated relatively more efficiently at suboptimal temperatures in "cold-blooded" vertebrate cells than in the hamster cells. Studies of [(3)H]uridine incorporation into uninfected BHK/21 cells incubated at different temperatures revealed that [(3)H]uridine uptake is sharply reduced at temperatures below 24.5 C. Growth curve studies of SVC virus in BHK/21 cells incubated at 23 C revealed that a clear-cut large excess of virus-induced [(3)H]uridine incorporation could be demonstrated in the absence of actinomycin D. Actinomycin D treatment (1 mug/ml) led to efficient inhibition of control cell [(3)H]uridine uptake, but also markedly reduced the total counts per minute of virus-induced [(3)H]uridine uptake, without depressing the yield of released infectious virus. Actinomycin D added to SVC virus-infected BHK/21 cell cultures at concentrations as low as 0.01 mug/ml caused a significant decrease in the level of virus-induced [(3)H]uridine uptake, despite the fact that this concentration is insufficient to efficiently suppress "background" cellular [(3)H]uridine incorporation.

Electron microscopy of the suckling mouse cataract agent: a noncultivable animal pathogen possibly related to mycoplasma

The suckling mouse cataract agent (SMCA) is a filtrable (<220 nm), noncultivable agent isolated from ticks in Georgia in 1961. It grows to high titer in the eyes and brains of intracerebrally inoculated mice in which it induces cataract, uveitis, and chronic brain infection. SMCA in high titer may also be recovered from the tissues of embryonated hen eggs in which the infection is lethal within 4 to 9 days. Fine-structural studies of ultrathin sections of pellets obtained by ultracentrifugation of SMCA-infected egg allantoic fluids have revealed pleomorphic structures with morphological characteristics typical of mycoplasma. Similar organisms have been observed in egg allantoic fluids infected with an SMCA-related tick isolate, GT-48, but not in fluids from uninoculated control eggs. Mycoplasma-like entities were also observed in high concentration within retinal tissues of rats and mice studied at the time of maximal retinitis and uveitis after SMCA inoculation. Comparable tissues from normal mouse eyes were free of microorganisms. These fine-structural observations are in agreement with those reported by other investigators and suggest that SMCA-induced pathology is associated with an agent that resembles mycoplasma in size and morphology but differs from typical mycoplasma in its apparent non-cultivability on artificial media and its resistance to inactivation by broad-spectrum antibiotics.

Detection of homologous RNA sequences among six rhabdovirus genomes

Complete transcripts of the genome of vesicular stomatitis virus Indiana strain have been used to hybridize to virion RNA to determine if there is RNA sequence homology among these viruses. Cellular RNA from cells infected by each of these viruses has also been used for hybridization with the homologous or heterologous virion RNA. The results indicate that there is little exact sequence homology among these viruses.