Transcript Slide 1

Future directions for
agricultural biotechnology
Dr. Kirstin Carroll
Outreach in Biotechnology Program
Oregon State University
Lecture Outline
• What is biopharming?
• Why use plants?
• Current and evolving regulation
• What are the risks and concerns?
What is biopharming?
The use of agricultural plants for the production of
useful molecules for non food, feed or fiber
applications. (also called molecular farming,
pharming, or biopharming)
What is biopharming?
The use of agricultural plants for the production of
useful molecules for non food, feed or fiber
applications. (also called molecular farming,
pharming, or biopharming)
Plants are already grown to produce valuable
molecules, including many drugs.
Biopharming is different because the plants are
genetically engineered (GE) to produce the
molecules we want them to.
Plant Products
1. Plant derived pharmaceuticals (non-GE)
• Over 120 pharmaceutical products currently in
use are derived from plants. Mainly from tropical
forest species (e.g. Taxol from Yew trees)
Plant Products
1. Plant-derived pharmaceuticals (non-GE)
2. Plant-made pharmaceuticals (PMPs) and
industrial products (PMIP) (GE)
Industrial products
• proteins
• enzymes
• modified starches
• fats
• oils
• waxes
• plastics
Pharmaceuticals
• recombinant human
proteins
• therapeutic proteins and
pharmaceutical
intermediates
• antibodies (plantibodies)
• vaccines
Strategies for Biopharming
1. Plant gene expression strategies
• Transient transformation
• adv. – quick and easy production
• disadv. – small amount of product, processing pblms
• Stable transformation
•
•
adv. – use for producing large quantities of protein, stability
and storage
disadv – gene flow - outcrossing w/native species
• Chloroplast transformation
• adv. – reduce gene flow through pollen
• disadv. – protein not stable for long periods of time
therefore complications w/extraction/processing times
Strategies for Biopharming
1. Plant gene expression strategies
2. Location of transgene expression
Protein quantity and preservation
• Whole plant
• adv. - an obtain large amts of protein
• disadv. - problems w/preservation
•
examples - tobacco, alfalfa, duckweed
• Target specific tissues (e.g. seed, root)
•
•
adv. - high amts of protein in seed/root, long-term
storage capability.
examples: soy, corn, rice, barley
Strategies for Biopharming
1. Plant gene expression system
2. Location of trans-gene expression
3. Selection of plant species and characteristics
• Mode of reproduction – self/outcrossing
• Yield, harvest, production, processing
Why use plants?
Advantages
Disadvantages
Cost reduction
Environment
contamination
- scalability (e.g. Enbrel® )
- low/no inputs
- low capital cost
Stability
- storage
Safety
- eukaroytic production system
- free of animal viruses (e.g.
BSE)
- gene flow
- wildlife exposure
Food supply
contamination
- mistaken/intentional mixing
w/human food
Health safety
concerns
- Variable, case-specific
Industrial products on the market
Avidin by Sigma
• transgenic corn
• traditionally isolated from chicken egg whites
• used in medical diagnostics
GUS (b-glycuronidase) by Sigma
• transgenic corn
• traditionally isolated from bacterial
sources (E.Coli)
• used as visual marker in research labs
Trypsin by Sigma
• transgenic corn
• traditionally isolated from bovine pancreas
• variety of applications, including biopharmaceutical
processing
• first large scale transgenic plant product
• Worldwide market = US$120 million in 2004
Industrial products close to market
Plant-made Pharmaceuticals (PMPs)
• Plant- made vaccines (edible vaccines)
• Plant-made antibodies (plantibodies)
• Plant-made therapeutic proteins and
intermediates
Unlike PMIPs, no PMPS are currently available
on the market
Plant-made Vaccines
Edible vaccines
Advantages:
Administered directly
• no purification required
• no hazards assoc. w/injections
Production
• may be grown locally, where needed most
• no transportation costs
Naturally stored
• no need for refrigeration or special storage
Plant-made Vaccines
Examples of edible vaccines under development:
• pig vaccine in corn
• HIV-suppressing protein in spinach
• human vaccine for hepatitis B in potato
Plantibodies
• Plantibodies - monoclonal antibodies produced
in plants
• Plants used include tobacco, corn, potatoes,
soy, alfalfa, and rice
• Free from potential contamination of
mammalian viruses
• Examples: cancer, dental caries, herpes
simplex virus, respiratory syncytial virus
Plantibodies
Dental Caries MAb– expected to reach the market
soon
MAb directed against genital herpes – estimated to
reach market within 5 years
(Horn et al, 2004)
**GE Corn can produce up to 1 kg antibody/acre
and can be stored at RT for up to 5 years.
Humphreys DP et al. Curr Opin Drug Discover Dev 2001; 4:172-85.
Plant made Pharmaceuticals
Therapeutic proteins and intermediates
• Blood substitutes – human hemoglobin
• Proteins to treat diseases such as CF, HIV,
Hypertension, Hepatitis B…..many others
Plant made Pharmaceuticals
**To date, there are no plant-produced
pharmaceuticals commercially available
Patient advocacy groups:
American Autoimmune Related Diseases Association
Arthritis Foundation
Cystic Fibrosis Foundation
Current ‘Pharm’ Companies
Current ‘Pharm’ Companies
•LEX System™
•Lemna (duckweed)
Kentucky Tobacco Research and
Development Center
•trangenic tobacco
•PMPs and non-protein substances
(flavors and fragrances, medicinals,
and natural insecticides)
Controlled Pharming Ventures
•collaboration w/Purdue
•transgenic corn
•converted limestone mine facility
Current ‘Pharm’ Companies
•biomass biorefinery
•based on switchgrass.
•used to produce PHAs
in green tissue plants
for fuel generation.
Rhizosecretion
• Monoclonal antibodies
(Drake et al., 2003)
• Recombinant proteins
(Gaume et al, 2003)
Examples of Current Research
• Genetically engineered Arabidopsis plants can
sequester arsenic from the soil. (Dhankher et al. 2002
Nature Biotechnology)
• Immunogenicity in human of an edible vaccine for
hepatitis B (Thanavala et al., 2005. PNAS)
• Expression of single-chain antibodies in transgenic
plants. (Galeffi et al., 2005 Vaccine)
• Plant based HIV-1 vaccine candidate: Tat
protein produced in spinach. (Karasev et al. 2005
Vaccine)
• Plant-derived vaccines against diarrheal diseases.
(Tacket. 2005 Vaccine)
Risks and Concerns
Environment contamination
• Gene flow via pollen
• Non-target species near field sites
e.g. butterflies, bees, etc
Food supply contamination
• Accident, intentional, gene flow
Health safety concerns
• Non-target organ responses
• Side-effects
• Allergenicity
U.S. Regulatory System
(existing regulations)
USDA
FDA
EPA
Field Testing
-permits
-notifications
Food safety
Pesticide and
herbicide
registration
Determination of
non-regulated
status
Feed safety
Breakdown of Regulatory
System: Prodigene Incident 2002
2001 : Field trails of GE corn producing
pig vaccine were planted in IA and NE.
2002: USDA discovered “volunteer”
corn plants in fields in both IA and NE.
Soy was already planted in NE site.
$500,000 fine + $3 million to buy/destroy contaminated
soy
USDA Response to Incident
Revised regulations so that they were distinct from
commodity crops:
• Designated equipment must be used
• At least 5 inspections/yr
• Pharm crops must be grown at least 1 mile away
from any other fields and planted 28 days
before/after surrounding crops
Current Evolving Regulations
FDA/USDA Guidance for Industry on Plant-Made
Pharmaceuticals Regulations
November 2004: Draft Document
Other challenges:
•Industrial hygiene and safety programs – these will
depend on the activity of the protein, route of exposure.
•Difficulty in obtaining relevant data because of high
species-specificity.
(Goldstein, 2005)
Biopharming field trials in the US
www.ucsusa.org
Since 1995 ~ 300 biopharming plantings
The USDA receives/reviews applications for permits
for biopharm trials.
Biopharming field trials in the US
www.ucsusa.org
US Pharma Crop Database
http://go.ucsusa.org/food_and_environment/pharm/index.php?s_keyword=XX
Biopharming in Colorado
Biopharming in N.Carolina
The 2005 Oregon Biopharm Bill
Biopharm opposition
Main concern is containment.
Opponents want:
• a guarantee of 0% contamination
of the food supply.
• full disclosure of field trials, crop,
gene, location, etc.
• an extensive regulatory framework
Suggested Safeguards for
biopharm operations
1. Physical differences
• e.g. “purple” maize, GFP
2. Sterility
• male sterile plants
• terminator technology
3. Easily detectable by addition of 'reporter
genes‘
• e.g. PCR markers
Suggested Safeguards for
biopharm operations
4. Use chloroplast expression system
• will help increase yield
• will eliminate potential gene flow via pollen
• disadv. = technically difficult (Chlorogen
Company)
5. Complete disclosure of DNA sequences
6. Legislate for administration
Alternatives to biopharming?
Use only traditional drug production systems
•microbial, yeast and fungi
•mammalian cell culture
Use only fully contained production systems:
•plant cell cultures
•hydroponics (rhizosecretion)
•greenhouses
Use non-food crops
•tobacco
•hemp/cannabis
Economics
The expectation is for lower production costs
however there is no evidence that pharming
will produce cheaper, safe drugs.
Moreover, there are unknown costs associated
with containment, litigation and liability,
production…..others?
Future directions for
agricultural biotechnology?
Science has developed genetically enhanced crops and
has/can develop plant-made industrial and
pharmaceuticals crops.
The extent to which these crops will be further developed
for commercial and/or humanitarian use will ultimately
depend on…..
Public perception
of risk
Regulation
Discussion Questions:
Do you think nutritionally enhanced plants
should be developed even though there are oral
supplements available? Why or why not?
Do you support the development of pharm
crops? Do you feel that the potential benefits
of pharm crops are worth the potential risks?
What are your thoughts on using food vs. nonfood crops as “phactories” for pharmaceutical
or industrial protein production?
Linkage Discussion Questions:
In the lecture on sustainability, Proebsting painted a picture
that all of conventional ag is so out of whack in its
water/energy/soil effects that biotech’s benefits are, by
implication, irrelevant. Is that what he meant? Do you
agree or disagree with this basic view? Why or why not?
In the lecture on organic ag, Stone showed the many ways in
which farmers can work to improve soil quality and reduce
energy use. The list of “excluded practices” aside, in what
ways are the goals of organic ag the same or different from
conventional and other sustainable forms of ag?
The first generation of GMO crops are often cited as having
benefits for farmers and seed companies but not for
consumers/public. In what ways is this true or false?
Potrykus painted a picture of a regulatory system so out of
whack that GMO crops with huge potential benefits for the
poor and ill are held up to the same or a greater degree as
are crops whose main beneficiaries might be agribusiness
or the developed world. Do you agree? What should a
smart system look like? How would it compare to the
system in use for conventionally bred crops?
Genetic pollution is often cited as unmanageable and thus a
reason not to completely exclude biotech crops in entire
countries or states. But toxicology teaches us that “the
dose makes the poison” (thus, by analogy its not a
pollutant in consequence unless it is above a given
threshold). Should adventitious presence be called
pollution/contamination at all? When? How should it be
dealt with by society?