Friday, 21 November 2008

Engineered Food and the FDA

To get bioengineered medicines, grains, vegetables, and animals on the market for human consumption, U.S. biotech companies must pass their products through the Food and Drug Administration (FDA).
Recently, the FDA has been in the news because its Prescription Drug User Fee Act of 1992, which forces drug companies to pay in to expedite drug approval, came up for renewal. That same year, the FDA rejected mandatory labeling of genetically modified organism (GMO) products. How might the FDA affect the future of bioengineered food?

The User Fee Act has, in Harvard professor Jerry Avorn's opinion, "pretty much transformed the FDA. The sense now is we report to the industry; they pay our salaries; we had better be quick on these approvals."
Some biotech products will zoom through the FDA because they are advances in medical treatment, and, of course, we all want the sick to get the best new therapies. The problem is that the FDA is underfunded, so most resources are dedicated to medical advances. Thus, according to David Kessler of the FDA, "other parts of the agency—post-market surveillance, food safety, the field resources—those areas of the agency suffer."

In addition, the FDA is essentially rubber-stamping the tests performed by each company that has developed a product, and since they're bogged down in analysis of drug tests, they hardly ever follow up on the market to see if bioengineered products are having a negative impact on consumers. One publicized mishap in 2000 resulted in traces of StarLink Bt10 corn, meant only for industrial purposes, cross-pollinating with conventional corn and winding up in taco shells. We know the FDA isn't catching problems like this one--and that, as yet, consuming products deemed marginally unsafe won't cause an epidemic—but eventually the biotech industry may get consumer backlash for causing a serious problem that could have been avoided if the budget were expanded.

I should probably note that the U.S. Department of Agriculture (USDA) oversaw the restrictions on this brand of corn, and the Department of Health and Human Services, of which the FDA is a part, only posts notices for products consumed by humans—so there's a further complication for biologically engineered products. They may be subject to these two departments as well as the Environmental Protection Agency, and this structural weakness probably doesn't make for excellent communication.
One could argue that GMO labeling is only a minor issue in the U.S. and that the average citizen isn't too concerned about the provenance of his or her food. There are at least two problems with this attitude. The first is that U.S. exports will be increasingly suspect to foreign markets, particularly the EU, which require labeling and stringent testing. The second is that any misstep, such as a genetically engineered product that results in widespread sickness, will create distrust of the FDA and bioengineering in general.

Europe's vigorous standards regarding approval, track-back, and isolation for GMO crops may be driving North America out of the market. Agricultural specialists like Dan McGuire are questioning if GMO crops are really to their economic advantage.
"I can't recall any foreign or domestic corn customer ever requesting that U.S. farmers start planting and supplying genetically engineered corn. So the introduction of GMOs was not a response to importers or consumers requesting such a change. Indeed, it's a direct result of biotech companies introducing those products into the domestic and foreign market without market research on consumer acceptance. Indeed, the first I heard about GMOs was from European importers," said McGuire.
Leaders in the biotechnology industry need to be activists for their products—labeling their products will bring them one step closer to informing the public and leading us into discussions of benefits like cheaper crop production and less pesticide runoff.

Friday, 7 November 2008

Types of Gene therapy and general strategies

Gene therapy may be classified into two types

1) Germ line gene therapy

2) Somatic cell gene therapy

a) Incase of germ line gene therapy germ cells that is sperms or eggs are modified by the introduction of functional genes, which are ordinarily integrated into their genomes.

Therefore the change due to therapy is heritable and passed onto the later generations. This approach, heretically, is highly effective in counteracting the genetic disorders. However this option is not consider, at least for the present for application in human beings for a variety of technical and ethical reasons.

b) In the case of somatic cell gene therapy the gene is introduced only in somatic cells, especially of those tissues in which expression of the concerned gene is critical for health. Expression of the introduced gene relieves symptoms of the disorder, but this effect is not heritable, as it does not involve the germ line. It is the only feasible option, and clinical trials have already started mostly for the treatment of cancer and blood disorders.


1) Gene augmentation therapy (GAT): -

It is done by simple addition of functional alleles has been used to treat several inherited disorders caused by genetic deficiency of a gene product. It is also involved in transfer to cells of genes encoding toxic compounds (suicide genes) or prodrugs (reagents which confer sensitivity to subsequent treatment with a drug). It has been particularly applied to autosomal recessive disorders where even modest expression levels of an introduced gene may make a substantial difference.

2) Targeted killing of specific cells: -

Artificial cell killing and immune system assisted cell killing have been popular in the treatment of cancers. It can be done by two ways.

a) Direct cell killing: - it is possible if the inserted genes are expressed to produce a lethal toxin (suicide genes), or a gene encoding a prodrug is inserted, conferring susceptibility to killing by a subsequently administered drug. Alternatively selectively lytic viruses can be used.

b) Indirect cell killing: - It uses immunostimulatory genes to provoke or enhance an immune response against the target cell.

3) Targeted mutation correction: -

The repair of a genetic defect to restore a functional allele, is the exception, technical difficulties have meant that it is not sufficiently reliable to warrant clinical trails.

4) Targeted inhibition of gene expression: -

It is suitable for treating infectious diseases and some cancers. If disease cells display a novel gene product or inappropriate expression of a gene a variety of different systems can be used specifically to block the expression of a single gene at the DNA, RNA or Protein levels.

1) Tom strachan and Andrew P. Read, Human Molecular Genetics, Second edition.

2) T.A. Brown, Gene Cloning an introduction, Third Edition.

3) S.N. Jogdand, Gene Biotechnology.

4) B.D Singh, Biotechnology.

Human Gene Therapy

Human beings suffer from more than 5000 different diseases caused by single gene mutations, e.g., cystic fibrosis acatalasis, hunting tons chorea, tay sachs disease, lisch nyhan syndrome, sickle cell anemia, mitral stenosis, hunter's syndrome, haemophilia, several forms of muscular dystrophy etc. In addition, many common disorders like cancer, hypertension, atherosclerosis and mental illness seem to have genetic components.

The term gene therapy can be defined as introduction of a normal functional gene into cells, which contain the defective allele of concerned gene with the objective of correcting a genetic disorder or an acquired disorder.
The first approach in gene therapy is: -

a) Identification of the gene that plays the key role in the development of a genetic disorder.

b) Determination of the role of its product in health and disease.

c) Isolation and cloning of the gene.

d) Development of an approach for gene therapy.

The genetic material may be transferred directly into cells within a patient, which is referred as in vivo gene therapy or else cells may be removed from the patient and the genetic material inserted into them, which is referred as invitro gene therapy. Apart from the two methods mentioned above there is one more method that is ex-vivo gene therapy in which genetic material is inserted into the cells just prior to transplanting the modified cells back into the patient.

Major disease classes under gene therapy include: -

a) Infectious diseases: - infection by a virus or bacterial pathogen

b) Cancers: - uncontrolled and enormous cell division and cell proliferation as a result of activation of an oncogene or inactivation of a tumors suppressor gene or an apoptosis gene.

c) Inherited disorders: - genetic deficiency of an individual gene product or genetically determined in appropriate expression of a gene.

d) Immune system disorders: - includes allergies, inflammation and also autoimmune diseases in which immune system cells appropriately destroy body cells.

Saturday, 1 November 2008

The human genome project

Although great strides have been made in gene therapy in a relatively short time, its potential usefulness has been limited by lack of scientific data concerning the multitude of functions that genes control in the human body. For instance, it is now known that the vast majority of genetic material does not store information for the creation of proteins, but rather is involved in the control and regulation of gene expression, and is, thus, much more difficult to interpret. Even so, each individual cell in the body carries thousands of genes coding for proteins, with some estimates as high as 150,000 genes. For gene therapy to advance to its full potential, scientists must discover the biological role of each of these individual genes and where the base pairs that make them up are located on DNA.

To address this issue, the National Institutes of Health initiated the Human Genome Project in 1990. Led by James D. Watson (one of the co-discoverers of the chemical makeup of DNA) the project's 15-year goal is to map the entire human genome (a combination of the words gene and chromosomes). A genome map would clearly identify the location of all genes as well as the more than three billion base pairs that make them up. With a precise knowledge of gene locations and functions, scientists may one day be able to conquer or control diseases that have plagued humanity for centuries.

Scientists participating in the Human Genome Project identified an average of one new gene a day, but many expected this rate of discovery to increase. By the year 2005, their goal was to determine the exact location of all the genes on human DNA and the exact sequence of the base pairs that make them up. Some of the genes identified through this project include a gene that predisposes people to obesity, one associated with programmed cell death (apoptosis), a gene that guides HIV viral reproduction, and the genes of inherited disorders like Huntington's disease, Lou Gehrig's disease, and some colon and breast cancers. In April 2003, the finished sequence was announced, with 99% of the human genome's gene-containing regions mapped to an accuracy of 99.9%.