K-series centrifuges. I. Development of the K-II continuous-sample-flow-with-banding centrifuge system for vaccine purification

Assembly and Electronic Applications of Colloidal Nanomaterials

Artificial solids and thin films assembled from colloidal nanomaterials give rise to versatile properties that can be exploited in a range of technologies. In particular, solution-based processes allow for the large-scale and low-cost production of nanoelectronics on rigid or mechanically flexible substrates. To achieve this goal, several processing steps require careful consideration, including nanomaterial synthesis or exfoliation, purification, separation, assembly, hybrid integration, and device testing. Using a ubiquitous electronic device - the field-effect transistor - as a platform, colloidal nanomaterials in three electronic material categories are reviewed systematically: semiconductors, conductors, and dielectrics. The resulting comparative analysis reveals promising opportunities and remaining challenges for colloidal nanomaterials in electronic applications, thereby providing a roadmap for future research and development.

Sorting carbon nanotubes by electronic structure using density differentiation

The heterogeneity of as-synthesized single-walled carbon nanotubes (SWNTs) precludes their widespread application in electronics, optics and sensing. We report on the sorting of carbon nanotubes by diameter, bandgap and electronic type using structure-discriminating surfactants to engineer subtle differences in their buoyant densities. Using the scalable technique of density-gradient ultracentrifugation, we have isolated narrow distributions of SWNTs in which >97% are within a 0.02-nm-diameter range. Furthermore, using competing mixtures of surfactants, we have produced bulk quantities of SWNTs of predominantly a single electronic type. These materials were used to fabricate thin-film electrical devices of networked SWNTs characterized by either metallic or semiconducting behaviour.

Global screening for human viral pathogens

We propose a system for continuing surveillance of viral pathogens circulating in large human populations. We base this system on the physical isolation of viruses from large pooled samples of human serum and plasma (e.g., discarded specimens from diagnostic laboratories), followed by shotgun sequencing of the resulting genomes. The technology for concentrating virions from 100-L volumes was developed previously at Oak Ridge National Laboratory, and the means for purifying and concentrating virions from volumes in microliters have been developed recently. At the same time, marine virologists have developed efficient methods for concentrating, amplifying, and sequencing complex viral mixtures obtained from the ocean. Given this existing technology base, we believe an integrated, automated, and contained system for surveillance of the human "virome" can be implemented within 1 to 2 years. Such a system could monitor the levels of known viruses in human populations, rapidly detect outbreaks, and systematically discover novel or variant human viruses.

Large-scale oligonucleotide synthesizers. I. Basic principles and system design

The central problem in scaling up oligonucleotide synthesis is to expose each element of a large bed to the same conditions obtaining in very small ones, for the same intervals of time. Our analysis suggests that scale-up is chiefly limited by fluid path length through the bed. By using annular beds in zonal centrifuge rotors of unique design, with fluid flow controlled by combining centrifugal force with differences in physical density between reagents, reagent fronts may be kept exactly perpendicular to the direction of flow in each bed element. Under these conditions, bed volume may be increased by increasing rotor length and diameter. The rotor is lined with polypropylene or Teflon, and has a thick tempered glass end window. Transparent rotary valves of a unique design allow any of 47 reagents to be selected and the direction of flow through the rotor to be controlled. A photodiode spectrophotometer provides complete absorption spectra on fluid in the rotor inlet and outlet lines every 4 s, and a large balance weighs effluent from the synthesizer continuously. The entire operation is controlled by a work station, and steps may be programmed by time, absorbance, or reagent mass. Reagents are identified by spectra, and trityls are integrated on line. A detailed time-stamped log file provides a complete record of each synthesis.

Preclinical investigations of the safety, immunogenicity and efficacy of a purified, inactivated tick-borne encephalitis vaccine

A new tick-borne encephalitis (TBE) vaccine for human use has been developed. TBE virus (TBEV) was propagated in primary chick embryo cells, inactivated by formalin and purified by continuous-flow density gradient centrifugation. The TBE vaccine was tested for innocuity, immunogenicity and protective capacity in a series of laboratory tests. The results indicated that the vaccine is outstandingly well tolerated, highly immunogenic in various laboratory animals, and induces protective immunity in mice. These data suggest that this new vaccine should be studied in clinical trials.

Immunogenicity and reactogenicity of a highly purified vaccine against tick-borne encephalitis

Immunogenicity and reactogenicity of a vaccine containing inactivated tick-borne encephalitis virus prepared by continuous flow zonal ultracentrifugation were compared with those of a previously used, less purified vaccine. Antibody response as measured by hemagglutination inhibition (HI) and enzyme-linked immunosorbent assay (ELISA) was 93% after two vaccinations and 100% after a third dose. The zonally purified vaccine impressively reduced the incidence of side reactions. Pyrexia (greater than 37.3 degrees C) was recorded in only 4--10% of the vaccinees almost exclusively after first vaccinations compared to 17--68% with the old type of vaccine. When these results are evaluated according to criteria commonly used in the United States (ie, pyrexia greater than 100 degrees F = 37.8 degrees C), almost no fewer would be recorded. The frequency of systemic side reactions was even lower (statistically significant) after second and third vaccination. This highly purified vaccine therefore represents an effective and well-tolerated means for the immunoprophylaxis of TBE.

Preparation of a highly purified vaccine against tick-borne encephalitis by continuous flow zonal ultracentrifugation

By the use of continuous-flow zonal ultracentrifugation, a highly purified, inactivated tick-borne encephalitis (TBE) virus vaccine was prepared tht contained almost exclusively TBE virus particles. The purity of this preparation was 90- to 100-fold higher than that of a previously used partially purified vaccine. A mean protein content of 3-5 microgram/ml in the final vaccine represents 20 mouse protective doses50 in a mouse challenge potency test. This high degree of purity resulted in a strong reduction of side reactions observed with the less purified vaccine.

Simultation of gradient and band propagation in the centrifuge

A technique is developed for simulating the behavior of both the gradient-forming solute and macromolecular bands in a centrifuge. The change with time of the density gradient due to diffusion and sedimentation of the gradient-forming solute is calculated by a finite difference method, making use of the results of earlier work on the theory of the equilibrium density gradient. Using a perturbation technique, the concentration profiles of dilute bands of macromolecules are then calculated as they sediment and diffuse through the varying supporting gradient. Results of the stimulaion techniques are compared with experiment.

Biohazards assessment in large-scale zonal centrifugation

A study was conducted to determine the biohazards associated with use of the large-scale zonal centrifuge for purification of moderate risk oncogenic viruses. To safely and conveniently assess the hazard, coliphage T3 was substituted for the virus in a typical processing procedure performed in a National Cancer Institute contract laboratory. Risk of personnel exposure was found to be minimal during optimal operation but definite potential for virus release from a number of centrifuge components during mechanical malfunction was shown by assay of surface, liquid, and air samples collected during the processing. High concentration of phage was detected in the turbine air exhaust and the seal coolant system when faulty seals were employed. The simulant virus was also found on both the centrifuge chamber interior and rotor surfaces.

Purification of Japanese encephalitis virus vaccine by zonal centrifugation

A large-scale procedure for purification and concentration of Japanese encephalitis virus vaccine by a continuous-flow isopycnic banding technique in a sucrose density gradient solution, using a K-III zonal centrifuge rotor, is presented. The quality of zonal-purified vaccine was compared with commercial and Japanese National Institutes of Health reference vaccines for antigenicity, immunodiffusion, and allergic encephalitogenicity tests to show its high purity.

Large-scale purification of ribonucleic acid tumor viruses by use of continuous-flow density gradient centrifugation

This report describes a 200- to 300-fold increase in the quantity of ribonucleic acud tumor virus particles previously isolated at one time by zonal centrifugation.

Immune response in primates vaccinated with duck embryo cell culture rabies vaccine

Adult rhesus monkeys (Macaca mulata) were vaccinated with four inactivated rabies vaccines, including two cell culture vaccines, one zonal purified cell culture vaccine, and a 10% extracted duck embryo vaccine. The vaccines were potency tested by both National Institutes of Health (NIH) and Habel methods and passed one or both tests. However, a vaccine having acceptable potency by one method frequently failed or was marginal by the other procedure. Groups of three monkeys were inoculated with each vaccine by one of two schedules. The first consisted of four weekly 1-ml doses followed by a 1-ml booster dose at 6 months, and the second consisted of seven daily 1-ml doses of vaccine with no booster. Both zonal purified and extracted duck embryo vaccines induced detectable neutralizing antibody by day 7 with either schedule, and antibody titers elicited by the cell culture vaccine remained high through 210 days. However, antibody titers produced by the 10% duck embryo vaccine dropped sharply after their 28-day peak. Duck embryo cell culture vaccines with low or marginal potency as measured by Habel or NIH tests still produced rapid, high levels of serum-neutralizing antibody in primates. LD(50) or NIH and Habel tests as measured in mice were not necessarily good indices of antibody response in the primate host. The need for a cell culture potency test that will yield a more predictable correlation with the definitive host's antibody response is discussed.

Mass purification of nucleopolyhedrosis virus inclusion bodies in the K-series centrifuge

Nucleopolyhedrosis virus inclusion bodies specific for Hemerocampa pseudotsugata, Neodiprion sertifer, Porthetria dispar, and Heliothis zea have been purified by using a continuous-sample-flow-with-isopycnic-banding centrifuge in quantities up to 6 x 10(13) polyhedral inclusion bodies per day. Continuous-flow methods for S-rho type purification have been evolved to deal with mass isolation of bioparticles.

Virus in water. II. Evaluation of membrane cartridge filters for recovering low multiplicities of poliovirus from water

The efficiency of a Millitube MF cartridge filter, a membrane filter, for recovery of poliovirus from 100-gal volumes of both fresh (tap) and estuarine water was determined. In the high multiplicity of virus input-output experiments, recovery of 97% or greater of input virus was achieved in both types of water when the final concentration of divalent cation as Mg(2+) was 1,200 mug/ml and the pH was 4.5. Virus was effectively eluted from the membrane cartridge with 5x nutrient broth in 0.05 M carbonate-bicarbonate buffer at pH 9.0. Four elutions of 250 ml each were used. In the low multiplicity of virus input-output experiments under the same cationic and pH conditions, up to 67% of the input virus was recovered when the virus was further concentrated from the eluates by the aqueous polymer two-phase separation technique. The volume reduction was 126,000-190,000 to 1. The use of the combined techniques, i.e., membrane adsorption followed by aqueous polymer two-phase separation, provided a highly sensitive, simple, and remarkably reliable sequential methodology for the quantitative recovery of poliovirus occurring at multiplicities as low as 1 to 2 plaque-forming units per 5 gal of water.

Large-volume purification of tumor viruses by use of zonal centrifuges

Large volumes of fluids from selected cell cultures producing ribonucleic acid tumor viruses were processed by a double sucrose density gradient procedure using zonal centrifuges. The primary recovery utilized a Model K continuous-flow zonal centrifuge at 9 to 11 liters/hr. The virus zone from the Model K gradient was further purified on a second gradient in a B-29 rotor. The resulting viral concentrates at 2 x 10(11) particles per ml showed high purity by electron microscopy and gel analysis and were useful reagents in biochemical and immunological studies of the reverse transcriptase enzyme, virus structure, complement fixation, and other virus properties. Similar recovery methods were applied to other tumor virus systems.

Zonal-centrifuged purified duck embryo cell culture rabies vaccine for human vaccination

Rabies virus produced in duck embryo cell culture was concentrated from volumes of 14 to 30 liters to 400 to 800 ml by zonal centrifugation. Virus titers of peak fractions were from 100- to 1,000-fold greater than those of the starting material. Vaccines were prepared by combining fractions with peak virus titers and diluting back to 10 times concentration. The resulting beta-propiolactone-inactivated vaccines, when prepared as lyophilized vaccines with AlPO(4) adjuvant diluents, were low in protein nitrogen (0.01 mg/ml), and three of four lots passed the National Institutes of Health potency test when tested as equivalent to a standard 10% suspension of duck embryo or mouse brain tissue vaccine. These vaccines also induced good sero-conversion in adult rabbits after a single 1-ml dose of vaccine. Guinea pigs sensitized with zonal-centrifuged purified duck embryo vaccine (with AlPO(4) adjuvant) did not exhibit anaphylactic shock reactions when challenged with homologous vaccine. Also, no anaphylactic shock reactions were observed when guinea pigs were sensitized with either a 10% experimental duck embryo vaccine or cell culture vaccine and then challenged with the zonal-purified vaccine. However, guinea pigs sensitized with cell culture or zonal-purified vaccine and then challenged with the 10% experimental vaccine did show slight transitory congestion. The 10% experimental whole duck embryo vaccine was responsible for all observed anaphylactic shock reactions whether homologous or heterologous.