Organic compounds -- part of the class 532-570 series – Organic compounds – Carbohydrates or derivatives
Reexamination Certificate
1999-12-17
2001-10-16
Allen, Marianne P. (Department: 1631)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carbohydrates or derivatives
C435S420000, C536S026420, C514S783000, C424S195110
Reexamination Certificate
active
06303779
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for isolating and purifying viruses, soluble proteins and peptides produced in plants. More specifically, the present invention is applicable on a large scale.
BACKGROUND OF THE INVENTION
Plant proteins and enzymes have long been exploited for many purposes, from viable food sources to biocatalytic reagents, or therapeutic agents. During the past decade, the development of transgenic and transfected plants and improvement in genetic analysis have brought renewed scientific significance and economical incentives to these applications. The concepts of molecular plant breeding and molecular plant fanning, wherein a plant system is used as a bioreactor to produce recombinant bioactive materials, have received great attention.
Many examples in the literature have demonstrated the utilization of plants or cultured plant cells to produce active mammalian proteins, enzymes, vaccines, antibodies, peptides, and other bioactive species. Ma et al. (
Science
268:716-719 (1995)) were the first to describe the production of a functional secretory immunoglobulin in transgenic tobacco. Genes encoding the heavy and light chains of murine antibody, a murine joining chain, and a rabbit secretory component were introduced into separate transgenic plants. Through cross-pollination, plants were obtained to co-express all components and produce a functionally active secretory antibody. In another study, a method for producing antiviral vaccines by expressing a viral protein in transgenic plants was described (Mason et al.,
Proc. Natl. Acad. Sci. USA
93: 5335-5340 (1996)). The capsid protein of Norwalk virus, a virus causing epidemic acute gastroenteritis in humans was shown to self-assemble into virus-like particles when expressed in transgenic tobacco and potato. Both purified virus-like particles and transgenic potato tubers when fed to mice stimulated the production of antibodies against the Norwalk virus capsid protein. Alternatively, the production and purification of a vaccine may be facilitated by engineering a plant virus that carries a mammalian pathogen epitope. By using a plant virus, the accidental shedding of virulent virus with the vaccine is abolished, and the same plant virus may be used to vaccinate several hosts. For example, malarial epitopes have been presented on the surface of recombinant tobacco mosiac virus (TMV) (Turpen et al.
BioTechnology
13:53-57 (1995)). Selected B-cell epitopes were either inserted into the surface loop region of the TMV coat protein or fused into the C terminus. Tobacco plants after infection contain high titers of the recombinant virus, which may be developed as vaccine subunits and readily scaled up. In another study aimed at improving the nutritional status of pasture legumes, a sulfur-rich seed albumin from sunflower was expressed in the leaves of transgenic subterranean clover (Khan et al.
Transgenic Res.
5:178-185 (1996)). By targeting the recombinant protein to the endoplasmic reticulum of the transgenic plant leaf cells, an accumulation of transgenic sunflower seed albumin up to 1.3 % of the total extractable protein could be achieved.
Work has also been conducted in the area of developing suitable vectors for expressing foreign genetic material in plant hosts. Ahlquist, U.S. Pat. No. 4,885,248 and U.S. Pat. No. 5,173,410 describe preliminary work done in devising transfer vectors which might be useful in transferring foreign genetic material into plant host cells for the purpose of expression therein. Additional aspects of hybrid RNA viruses and RNA transformation vectors are described by Ahlquist et al. in U.S. Pat. Nos. 5,466,788, 5,602,242, 5,627,060 and 5,500,360 all of which are herein incorporated by reference. Donson et al., U.S. Pat. No. 5,316,931 and 5,589,367, herein incorporated by reference, demonstrate for the first time plant viral vectors suitable for the systemic expression of foreign genetic material in plants. Donson et al. describe plant viral vectors having heterologous subgenomic promoters for the systemic expression of foreign genes. The availability of such recombinant plant viral vectors makes it feasible to produce proteins and peptides of interest recombinantly in plant hosts.
Elaborate methods of plant genetics are being developed at a rapid rate and hold the promise of allowing the transformation of virtually every plant species and the expression of a large variety of genes. However, in order for plant-based molecular breeding and farming to gain widespread acceptance in commercial areas, it is necessary to develop a cost-effective and large-scale purification system for the bioactive species produced in the plants, either proteins or peptides, especially recombinant proteins or peptides, or virus particles, especially genetically engineered viruses.
Some processes for isolating proteins, peptides and viruses from plants have been described in the literature (Johal, U.S. Pat. Nos., 4,400,471, Johal, 4,334,024, Wildman et al., 4,268,632, Wildman et al., 4,289,147, Wildman et al., 4,347,324, Hollo et al., 3,637,396, Koch, 4,233,210, and Koch, 4,250,197, the disclosure of which are herein incorporated by reference). The succulent leaves of plants, such as tobacco, spinach, soybean, and alfalfa, are typically composed of 10-20% solids, the remaining fraction being water. The solid portion is composed of a water soluble and a water insoluble portion, the latter being predominantly composed of the fibrous structural material of the leaf. The water soluble portion includes compounds of relatively low molecular weight (MW), such as sugars, vitamins, alkaloids, flavors, amino acids, and other compounds of relatively high MW, such as native and recombinant proteins.
Proteins in the soluble portion of plant biomass can be further divided into two fractions. One fraction comprises predominantly a photosynthetic protein, ribulose 1,5-diphosphate carboxylase (or RuBisCO), whose subunit molecular weight is about 550 kD. This fraction is commonly referred to as “Fraction 1 protein.” RuBisCO is abundant, comprising up to 25% of the total protein content of a leaf and up to 10% of the solid matter of a leaf. The other fraction contains a mixture of proteins and peptides whose subunit molecular weights typically range from about 3 kD to 100 kD and other compounds including sugars, vitamins, alkaloids, flavors, amino acids. This fraction is collectively referred to as “Fraction 2 proteins.” Fraction 2 proteins can be native host materials or recombinant materials including proteins and peptides produced via transfection or transgenic transformation. Transfected plants may also contain virus particles having a molecular size greater than 1,000 kD.
The basic process for isolating plant proteins generally begins with disintegrating leaf biomass and pressing the resulting pulp to produce “green juice”. The process is typically performed in the presence of a reducing agent or antioxidant to suppress unwanted oxidation. The green juice, which contains various protein components and finely particulate green pigmented material, is pH adjusted and heated. The typical pH range for the green juice after adjustment is between 5.3 and 6.0. This range has been optimized for the isolation of Fraction 1 protein (or ribulose 1,5-diphosphate carboxylase). Heating, which causes the coagulation of green pigmented material, is typically controlled near 50° C. The coagulated green pigmented material can then be removed by moderate centrifugation to yield “brown juice.” The brown juice is subsequently cooled and stored at a temperature at or below room temperature. After an extended period of time, e.g. 24 hours, ribulose 1,5-diphosphate carboxylase is crystallized from the brown juice. The crystallized Fraction 1 protein can subsequently be separated from the liquid by centrifugation. Fraction 2 proteins remain in the liquid, and they can be purified upon further acidification to a pH near 4.5. Alternatively, the crystal formation of ribulose 1,5-diphosphate carboxylase from brown jui
Garger Stephen J.
Holtz R. Barry
McCulloch Michael J.
Turpen Thomas H.
Allen Marianne P.
Gallegos Thomas
Halluin Albert P.
Kung Viola T.
Large Scale Biology Corporation
LandOfFree
Process for isolating and purifying viruses and sugars from... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Process for isolating and purifying viruses and sugars from..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for isolating and purifying viruses and sugars from... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2579151