Colorado tick fever virus in cell culture. II. Physical and chemical properties

Trent, Dennis W. (University of Oklahoma School of Medicine, Oklahoma City), and L. Vernon Scott. Colorado tick fever virus in cell culture. II. Physical and chemical properties. J. Bacteriol. 91:1282-1288. 1966.-Heat-inactivation kinetics for Colorado tick fever (CTF) virus grown in L cells indicated that more than one rate constant was involved for inactivation at each exposure temperature. An Arrhenius plot of the data indicated the inactivation rate constants to be dependent on the absolute temperature. The energy of activation, for thermal inactivation of the virus, was 17,289 calories per mole, with the Q(10) being 2.6. The optimal pH range for maintenance of CTF viral infectivity was determined to be 7.5 to 7.8. The infectivity of CTF virus was stable to freezing and thawing in diluents which contained: 50% calf serum, 20% glucose, 20% glycerol, 10% bovine serum albumin, 20 mm glutamine, and 2% gelatin. CTF virus replication was insensitive to inhibition by 5-fluoro-2'-deoxyuridine and 5-bromo-2'-deoxyuridine, whereas herpes simplex virus was markedly inhibited, as reported by others. Actinomycin D inhibited CTF virus replication when cells were pretreated for 24 and 12 hr prior to infection, but not when the inhibitor was added at the time of infection. The nucleic acid of CTF virus appears to be of the ribose type.     

Physicochemical properties of Nebraska calf diarrhea virus hemagglutinin.

Highly purified Nebraska calf diarrhea virus (NCDV) was prepared by cesium chloride density gradient centrifugation. The effect of temperature, pH, different concentrations of formaldehyde, chloroform, ether, ethyl alcohol, and methyl alcohol on NCDV hemagglutinin and virus morphology was studied. NCDV hemagglutinin was inactivated by temperature, pH 2.0, chloroform, ethyl alcohol, and methyl alcohol.     

Physicochemical properties of tipula iridescent virus

The molecular weight of Tipula iridescent virus, based on sedimentation and diffusion coefficients, was 5.51 × 10⁸, with hydration of 0.57 g of water per g of virus. Deoxyribonucleic acid content, based on total inorganic phosphorus liberated, was 19 ± 0.2%. At 260 mμ, the virus gave an uncorrected absorbance of 18.2 cm²/mg of virus and a light-scattering corrected absorbance of 9.8 cm²/mg of virus. Amino acid analyses of the virus protein revealed a remarkable similarity to Sericesthis iridescent virus. The possibility is discussed that the four iridescent insect viruses reported to date bear a strain relationship.     

Physicochemical properties of N4 virus solutions. I. Viscosity--temperature behavior

The viscosity–temperature behavior of N4 virus solution was investigated by using a Zimm type viscometer. The role of ionic strength (LiBr) and pH in the viscosity–temperature behavior was determined. Supporting measurements of the sedimentation coefficient, infectivity, and optical density are presented. The viscosity–temperature behavior generally includes a region of low viscosity, characteristic of the intact virus, followed, upon increasing temperature, by a rather abrupt increase of viscosity which corresponds to the ejection of native DNA from the protein shell, presumably through a suitable opening in the capside. The viscosity remains constant upon further increase of temperature until a second abrupt increase is observed which is shown to correspond to the degradation of the empty protein shell (ghost). Finally, at a still higher temperature, denaturation of DNA occurs. This sequence of events can be altered by changes in pH and ionic strength. Increasing LiBr concentration reduces the temperature of ghost degradation and raises the temperature of DNA ejection and DNA de naturation. It is suggested that polyelectrolyte effects play a controlling role in the ejection of native DNA and that the conformation of the latter within the protein shell is stabilized by a decrease of the electrostatic free energy due to the swamping effect of the co-ions.     

Bovine virus diarrhea-mucosal disease. II. Isolation and characterization of a cytopathogenic virus and experimental production of the disease.

A disease broke out in calves in the Tokachi district of Hokkaido. It induced pyrexia, respiratory symptoms, diarrhea, bloody feces, leukopenia, and sometimes erosion of the oral mucous membrane and muzzle. Its morbidity rate was 90% and its fatality rate 50%. Bovine virus diarrhea (BVD) virus was isolated from organs of dead calves and blood and feces of affected calves. It exhibited a cytopathic effect on calf kidney cell culture. Antisera against the Nose and the Oregon C24V strains of BVD virus showed an antibody titer of the same order against the homologous virus and the isolated strain. Antiserum against the isolated strain, however, showed much lower antibody titers against the Nose and the Oregon C24V strains than against the homologous virus. When inoculated with the isolated virus, two calves manifested acute symptoms, but recovered at any rate. One of them, however, suffered again from clinical infection and died eventually 37 days after inoculation. It presented pathological changes closely resembling those of the case of spontaneous infection. Virus was recovered from its principal organs, intestinal canal, and lymph nodes of various regions of the body.     

An encephalomyocarditis virus epizootic in a baboon colony.

Approximately 80 baboon deaths were caused by encephalomyocarditis virus (EMCV) infection in a 3060 member research and production colony. The epizootic extended over a 9-month period and occurred in baboons ranging from 1 day to 22 years of age. Acute death was the most common history. When clinical disease was detected, it was characterized by labored respiration associated with acute congestive heart failure. The salient necropsy findings were pulmonary congestion and edema, hydropericardium, hydrothorax, ascites, lymph node and splenic hypertrophy, and pale white-to-tan mottled hearts. The most significant histologic lesion was nonsuppurative necrotizing myocarditis. Placental infection with fetal loss occurred. Diagnosis was confirmed by light microscopy, transmission electron microscopy, virus culture, and serology. Rarely, EMCV-induced antibody persisted in surviving baboons for more than 24 months. EMCV-infected feral rats were the probable source of the virus and their control stopped the epizootic. No EMCV neutralizing antibody was detected in colony support personnel or chimpanzees.     

Multiple proteases from Streptomyces moderatus. II. Physicochemical and enzymatic properties of the extracellular proteases

The physicochemical and enzymatic properties of five different extracellular proteases of Streptomyces moderatus were studied. The first protease was found to be a metal chelator sensitive protease with a Mr of 21,000 +/- 1000 a and a pI of 4.6. The second enzyme was an anionic trypsin-like protease (Mr 19,000 +/- 1000; pI 3.8) with a Km value of 4.76 X 10(-4) M on N-benzoyl-L-arginine-p-nitroanilide. A Km value of 1.52 X 10(-4) M was obtained when N-benzoyl-L-arginine ethyl ester was used as the substrate. The other three enzymes were found to be serine alkaline proteases with Mr's of 22,000, 29,000, and 23,000 +/- 1000 and with respective pI's of 7.8, 8.4, and 9.2. All the proteases showed optimum activity in the alkaline pH range. One of the three proteases was found to possess chymotrypsin and elastase-like properties. All five proteases were found to be unstable at temperatures above 60 degrees C. Except the trypsin-like protease, which was stable only in acidic pH, all other enzymes were found to be stable over a wide range of pH.