Part 9 (2/2)

Biotechnology will provide the means to actually change your genes: not just designer babies will be feasible but designer baby boomers. We'll also be able to rejuvenate all of your body's tissues and organs by transforming your skin cells into youthful versions of every other cell type. Already, new drug development is precisely targeting key steps in the process of atherosclerosis (the cause of heart disease), cancerous tumor formation, and the metabolic processes underlying each major disease and aging process.

Can We Really Live Forever? An energetic and insightful advocate of stopping the aging process by changing the information processes underlying biology is Aubrey de Grey, a scientist in the department of genetics at Cambridge University. De Grey uses the metaphor of maintaining a house. How long does a house last? The answer obviously depends on how well you take care of it. If you do nothing, the roof will spring a leak before long, water and the elements will invade, and eventually the house will disintegrate. But if you proactively take care of the structure, repair all damage, confront all dangers, and rebuild or renovate parts from time to time using new materials and technologies, the life of the house can essentially be extended without limit. An energetic and insightful advocate of stopping the aging process by changing the information processes underlying biology is Aubrey de Grey, a scientist in the department of genetics at Cambridge University. De Grey uses the metaphor of maintaining a house. How long does a house last? The answer obviously depends on how well you take care of it. If you do nothing, the roof will spring a leak before long, water and the elements will invade, and eventually the house will disintegrate. But if you proactively take care of the structure, repair all damage, confront all dangers, and rebuild or renovate parts from time to time using new materials and technologies, the life of the house can essentially be extended without limit.

The same holds true for our bodies and brains. The only difference is that, while we fully understand the methods underlying the maintenance of a house, we do not yet fully understand all of the biological principles of life. But with our rapidly increasing comprehension of the biochemical processes and pathways of biology, we are quickly gaining that knowledge. We are beginning to understand aging, not as a single inexorable progression but as a group of related processes. Strategies are emerging for fully reversing each of these aging progressions, using different combinations of biotechnology techniques.

De Grey describes his goal as ”engineered negligible senescence”-stopping the body and brain from becoming more frail and disease-p.r.o.ne as it grows older.18 As he explains, ”All the core knowledge needed to develop As he explains, ”All the core knowledge needed to develop engineered negligible senescence engineered negligible senescence is already in our possession-it mainly just needs to be pieced together.” is already in our possession-it mainly just needs to be pieced together.”19 De Grey believes we'll demonstrate ”robustly rejuvenated” mice-mice that are functionally younger than before being treated and with the life extension to prove it-within ten years, and he points out that this achievement will have a dramatic effect on public opinion. Demonstrating that we can reverse the aging process in an animal that shares 99 percent of our genes will profoundly challenge the common wisdom that aging and death are inevitable. Once robust rejuvenation is confirmed in an animal, there will be enormous compet.i.tive pressure to translate these results into human therapies, which should appear five to ten years later. De Grey believes we'll demonstrate ”robustly rejuvenated” mice-mice that are functionally younger than before being treated and with the life extension to prove it-within ten years, and he points out that this achievement will have a dramatic effect on public opinion. Demonstrating that we can reverse the aging process in an animal that shares 99 percent of our genes will profoundly challenge the common wisdom that aging and death are inevitable. Once robust rejuvenation is confirmed in an animal, there will be enormous compet.i.tive pressure to translate these results into human therapies, which should appear five to ten years later.

The diverse field of biotechnology is fueled by our accelerating progress in reverse engineering the information processes underlying biology and by a growing a.r.s.enal of tools that can modify these processes. For example, drug discovery was once a matter of finding substances that produced some beneficial result without excessive side effects. This process was similar to early humans' tool discovery, which was limited to simply finding rocks and other natural implements that could be used for helpful purposes. Today we are learning the precise biochemical pathways that underlie both disease and aging processes and are able to design drugs to carry out precise missions at the molecular level. The scope and scale of these efforts are vast.

Another powerful approach is to start with biology's information backbone: the genome. With recently developed gene technologies we're on the verge of being able to control how genes express themselves. Gene expression is the process by which specific cellular components (specifically RNA and the ribosomes) produce proteins according to a specific genetic blueprint. While every human cell has the full complement of the body's genes, a specific cell, such as a skin cell or a pancreatic islet cell, gets its characteristics from only the small fraction of genetic information relevant to that particular cell type.20 The therapeutic control of this process can take place outside the cell nucleus, so it is easier to implement than therapies that require access inside it. The therapeutic control of this process can take place outside the cell nucleus, so it is easier to implement than therapies that require access inside it.

Gene expression is controlled by peptides (molecules made up of sequences of up to one hundred amino acids) and short RNA strands. We are now beginning to learn how these processes work.21 Many new therapies now in development and testing are based on manipulating them either to turn off the expression of disease-causing genes or to turn on desirable genes that may otherwise not be expressed in a particular type of cell. Many new therapies now in development and testing are based on manipulating them either to turn off the expression of disease-causing genes or to turn on desirable genes that may otherwise not be expressed in a particular type of cell.

RNAi (RNA Interference). A powerful new tool called RNA interference (RNAi) is capable of turning off specific genes by blocking their mRNA, thus preventing them from creating proteins. Since viral diseases, cancer, and many other diseases use gene expression at some crucial point in their life cycle, this promises to be a breakthrough technology. Researchers construct short, double-stranded DNA segments that match and lock onto portions of the RNA that are transcribed from a targeted gene. With their ability to create proteins blocked, the gene is effectively silenced. In many genetic diseases only one copy of a given gene is defective. Since we get two copies of each gene, one from each parent, blocking the disease-causing gene leaves one healthy gene to make the necessary protein. If both genes are defective, RNAi could silence them both, but then a healthy gene would have to be inserted. A powerful new tool called RNA interference (RNAi) is capable of turning off specific genes by blocking their mRNA, thus preventing them from creating proteins. Since viral diseases, cancer, and many other diseases use gene expression at some crucial point in their life cycle, this promises to be a breakthrough technology. Researchers construct short, double-stranded DNA segments that match and lock onto portions of the RNA that are transcribed from a targeted gene. With their ability to create proteins blocked, the gene is effectively silenced. In many genetic diseases only one copy of a given gene is defective. Since we get two copies of each gene, one from each parent, blocking the disease-causing gene leaves one healthy gene to make the necessary protein. If both genes are defective, RNAi could silence them both, but then a healthy gene would have to be inserted.22

Cell Therapies. Another important line of attack is to regrow our own cells, tissues, and even whole organs and introduce them into our bodies without surgery. One major benefit of this ”therapeutic cloning” technique is that we will be able to create these new tissues and organs from versions of our cells that have also been made younger via the emerging field of rejuvenation medicine. For example, we will be able to create new heart cells from skin cells and introduce them into the system through the bloodstream. Over time, existing heart cells will be replaced with these new cells, and the result will be a rejuvenated ”young” heart manufactured using a person's own DNA. I discuss this approach to regrowing our bodies below. Another important line of attack is to regrow our own cells, tissues, and even whole organs and introduce them into our bodies without surgery. One major benefit of this ”therapeutic cloning” technique is that we will be able to create these new tissues and organs from versions of our cells that have also been made younger via the emerging field of rejuvenation medicine. For example, we will be able to create new heart cells from skin cells and introduce them into the system through the bloodstream. Over time, existing heart cells will be replaced with these new cells, and the result will be a rejuvenated ”young” heart manufactured using a person's own DNA. I discuss this approach to regrowing our bodies below.

Gene Chips. New therapies are only one way that the growing knowledge base of gene expression will dramatically impact our health. Since the 1990s microarrays, or chips no larger than a dime, have been used to study and compare expression patterns of thousands of genes at a time. New therapies are only one way that the growing knowledge base of gene expression will dramatically impact our health. Since the 1990s microarrays, or chips no larger than a dime, have been used to study and compare expression patterns of thousands of genes at a time.23 The possible applications of the technology are so varied and the technological barriers have been reduced so greatly that huge databases are now devoted to the results from ”do-it-yourself gene watching.” The possible applications of the technology are so varied and the technological barriers have been reduced so greatly that huge databases are now devoted to the results from ”do-it-yourself gene watching.”24 Genetic profiling is now being used to:

Revolutionize the processes of drug screening and discovery. Microarrays can ”not only confirm the mechanism of action of a compound” but ”discriminate between compounds acting at different steps in the same metabolic pathway.” Microarrays can ”not only confirm the mechanism of action of a compound” but ”discriminate between compounds acting at different steps in the same metabolic pathway.”25Improve cancer cla.s.sifications. One study reported in Science demonstrated the feasibility of cla.s.sifying some leukemias ”solely on gene expression monitoring.” The authors also pointed to a case in which expression profiling resulted in the correction of a misdiagnosis. One study reported in Science demonstrated the feasibility of cla.s.sifying some leukemias ”solely on gene expression monitoring.” The authors also pointed to a case in which expression profiling resulted in the correction of a misdiagnosis.26Identify the genes, cells, and pathways involved in a process, such as aging or tumorigenesis. For example, by correlating the presence of acute myeloblastic leukemia and increased expression of certain genes involved with programmed cell death, a study helped identify new therapeutic targets. For example, by correlating the presence of acute myeloblastic leukemia and increased expression of certain genes involved with programmed cell death, a study helped identify new therapeutic targets.27Determine the effectiveness of an innovative therapy. One study recently reported in Bone looked at the effect of growth-hormone replacement on the expression of insulinlike growth factors (IGFs) and bone metabolism markers. One study recently reported in Bone looked at the effect of growth-hormone replacement on the expression of insulinlike growth factors (IGFs) and bone metabolism markers.28Test the toxicity of compounds in food additives, cosmetics, and industrial products quickly and without using animals. Such tests can show, for example, the degree to which each gene has been turned on or off by a tested substance. Such tests can show, for example, the degree to which each gene has been turned on or off by a tested substance.29

Somatic Gene Therapy (gene therapy for nonreproductive cells). This is the holy grail of bioengineering, which will enable us to effectively change genes inside the nucleus by ”infecting” it with new DNA, essentially creating new genes. (gene therapy for nonreproductive cells). This is the holy grail of bioengineering, which will enable us to effectively change genes inside the nucleus by ”infecting” it with new DNA, essentially creating new genes.30 The concept of controlling the genetic makeup of humans is often a.s.sociated with the idea of influencing new generations in the form of ”designer babies.” But the real promise of gene therapy is to actually change our adult genes. The concept of controlling the genetic makeup of humans is often a.s.sociated with the idea of influencing new generations in the form of ”designer babies.” But the real promise of gene therapy is to actually change our adult genes.31 These can be designed to either block undesirable disease-encouraging genes or introduce new ones that slow down and even reverse aging processes. These can be designed to either block undesirable disease-encouraging genes or introduce new ones that slow down and even reverse aging processes.

Animal studies that began in the 1970s and 1980s have been responsible for producing a range of transgenic animals, such as cattle, chickens, rabbits, and sea urchins. The first attempts at human gene therapy were undertaken in 1990. The challenge is to transfer therapeutic DNA into target cells that will then be expressed at the right level and at the right time.

Consider the challenge involved in effecting a gene transfer. Viruses are often the vehicle of choice. Long ago viruses learned how to deliver their genetic material to human cells and, as a result, cause disease. Researchers now simply switch the material a virus unloads into cells by removing its genes and inserting therapeutic ones. Although the approach itself is relatively easy, the genes are too large to pa.s.s into many types of cells (such as brain cells). The process is also limited in the length of DNA it can carry, and it may cause an immune response. And precisely where the new DNA integrates into the cell's DNA has been a largely uncontrollable process.32 Physical injection (microinjection) of DNA into cells is possible but prohibitively expensive. Exciting advances have recently been made, however, in other means of transfer. For example, liposomes-fatty spheres with a watery core-can be used as a ”molecular Trojan horse” to deliver genes to brain cells, thereby opening the door to treatment of disorders such as Parkinson's and epilepsy.33 Electric pulses can also be employed to deliver a range of molecules (including drug proteins, RNA, and DNA) to cells. Electric pulses can also be employed to deliver a range of molecules (including drug proteins, RNA, and DNA) to cells.34 Yet another option is to pack DNA into ultratiny ”nan.o.b.a.l.l.s” for maximum impact. Yet another option is to pack DNA into ultratiny ”nan.o.b.a.l.l.s” for maximum impact.35 The major hurdle that must be overcome for gene therapy to be applied in humans is proper positioning of a gene on a DNA strand and monitoring of the gene's expression. One possible solution is to deliver an imaging reporter gene along with the therapeutic gene. The image signals would allow for close supervision of both placement and level of expression.36 Even faced with these obstacles gene therapy is starting to work in human applications. A team led by University of Glasgow research doctor Andrew H. Baker has successfully used adenoviruses to ”infect” specific organs and even specific regions within organs. For example, the group was able to direct gene therapy precisely at the endothelial cells, which line the inside of blood vessels. Another approach is being developed by Celera Genomics, a company founded by Craig Venter (the head of the private effort to transcribe the human genome). Celera has already demonstrated the ability to create synthetic viruses from genetic information and plans to apply these biodesigned viruses to gene therapy.37 One of the companies I help to direct, United Therapeutics, has begun human trials of delivering DNA into cells through the novel mechanism of autologous (the patient's own) stem cells, which are captured from a few vials of their blood. DNA that directs the growth of new pulmonary blood vessels is inserted into the stem cell genes, and the cells are reinjected into the patient. When the genetically engineered stem cells reach the tiny pulmonary blood vessels near the lung's alveoli, they begin to express growth factors for new blood vessels. In animal studies this has safely reversed pulmonary hypertension, a fatal and presently incurable disease. Based on the success and safety of these studies, the Canadian government gave permission for human tests to commence in early 2005.

Reversing Degenerative Disease Degenerative (progressive) diseases-heart disease, stroke, cancer, type 2 diabetes, liver disease, and kidney disease-account for about 90 percent of the deaths in our society. Our understanding of the princ.i.p.al components of degenerative disease and human aging is growing rapidly, and strategies have been identified to halt and even reverse each of these processes. In Fantastic Voyage Fantastic Voyage, Grossman and I describe a wide range of therapies now in the testing pipeline that have already demonstrated significant results in attacking the key biochemical steps underlying the progress of such diseases.

Combating Heart Disease. As one of many examples, exciting research is being conducted with a synthetic form of HDL cholesterol called recombinant Apo-A-I Milano (AAIM). In animal trials AAIM was responsible for a rapid and dramatic regression of atherosclerotic plaque. As one of many examples, exciting research is being conducted with a synthetic form of HDL cholesterol called recombinant Apo-A-I Milano (AAIM). In animal trials AAIM was responsible for a rapid and dramatic regression of atherosclerotic plaque.38 In a phase 1 FDA trial, which included forty-seven human subjects, administering AAIM by intravenous infusion resulted in a significant reduction (an average 4.2 percent decrease) in plaque after just five weekly treatments. No other drug has ever shown the ability to reduce atherosclerosis this quickly. In a phase 1 FDA trial, which included forty-seven human subjects, administering AAIM by intravenous infusion resulted in a significant reduction (an average 4.2 percent decrease) in plaque after just five weekly treatments. No other drug has ever shown the ability to reduce atherosclerosis this quickly.39 Another exciting drug for reversing atherosclerosis now in phase 3 FDA trials is Pfizer's Torcetrapib.40 This drug boosts levels of HDL by blocking an enzyme that normally breaks it down. Pfizer is spending a record one billion dollars to test the drug and plans to combine it with its best-selling ”statin” (cholesterol-lowering) drug, Lipitor. This drug boosts levels of HDL by blocking an enzyme that normally breaks it down. Pfizer is spending a record one billion dollars to test the drug and plans to combine it with its best-selling ”statin” (cholesterol-lowering) drug, Lipitor.

Overcoming Cancer. Many strategies are being intensely pursued to overcome cancer. Particularly promising are cancer vaccines designed to stimulate the immune system to attack cancer cells. These vaccines could be used as a prophylaxis to prevent cancer, as a first-line treatment, or to mop up cancer cells after other treatments. Many strategies are being intensely pursued to overcome cancer. Particularly promising are cancer vaccines designed to stimulate the immune system to attack cancer cells. These vaccines could be used as a prophylaxis to prevent cancer, as a first-line treatment, or to mop up cancer cells after other treatments.41 The first reported attempts to activate a patient's immune response were undertaken more than one hundred years ago, with little success.42 More recent efforts focus on encouraging dendritic cells, the sentinels of the immune system, to trigger a normal immune response. Many forms of cancer have an opportunity to proliferate because they somehow do not trigger that response. Dendritic cells playa key role because they roam the body, collecting foreign peptides and cell fragments and delivering them to the lymph nodes, which in response produce an army of T cells primed to eliminate the flagged peptides. More recent efforts focus on encouraging dendritic cells, the sentinels of the immune system, to trigger a normal immune response. Many forms of cancer have an opportunity to proliferate because they somehow do not trigger that response. Dendritic cells playa key role because they roam the body, collecting foreign peptides and cell fragments and delivering them to the lymph nodes, which in response produce an army of T cells primed to eliminate the flagged peptides.

Some researchers are altering cancer-cell genes to attract T cells, with the a.s.sumption that the stimulated T cells would then recognize other cancer cells they encounter.43 Others are experimenting with vaccines for exposing the dendritic cells to antigens, unique proteins found on the surfaces of cancer cells. One group used electrical pulses to fuse tumor and immune cells to create an ”individualized vaccine.” Others are experimenting with vaccines for exposing the dendritic cells to antigens, unique proteins found on the surfaces of cancer cells. One group used electrical pulses to fuse tumor and immune cells to create an ”individualized vaccine.”44 One of the obstacles to developing effective vaccines is that currently we have not yet identified many of the cancer antigens we need to develop potent targeted vaccines. One of the obstacles to developing effective vaccines is that currently we have not yet identified many of the cancer antigens we need to develop potent targeted vaccines.45 Blocking angiogenesis-the creation of new blood vessels-is another strategy. This process uses drugs to discourage blood-vessel development, which an emergent cancer needs to grow beyond a small size. Interest in angiogenesis has skyrocketed since 1997, when doctors at the Dana Farber Cancer Center in Boston reported that repeated cycles of endostatin, an angiogenesis inhibitor, had resulted in complete regression of tumors.46 There are now many antiangiogenic drugs in clinical trials, including avastin and atrasentan. There are now many antiangiogenic drugs in clinical trials, including avastin and atrasentan.47 A key issue for cancer as well as for aging concerns telomere ”beads,” repeating sequences of DNA found at the end of chromosomes. Each time a cell reproduces, one bead drops off. Once a cell has reproduced to the point that all of its telomere beads have been expended, that cell is no longer able to divide and will die. If we could reverse this process, cells could survive indefinitely. Fortunately, recent research has found that only a single enzyme (telomerase) is needed to achieve this.48 The tricky part is to administer telomerase in such a way as not to cause cancer. Cancer cells possess a gene that produces telomerase, which effectively enables them to become immortal by reproducing indefinitely. A key cancer-fighting strategy, therefore, involves blocking the ability of cancer cells to generate telomerase. This may seem to contradict the idea of extending the telomeres in normal cells to combat this source of aging, but attacking the telomerase of the cancer cells in an emerging tumor could be done without necessarily compromising an orderly telomere-extending therapy for normal cells. However, to avoid complications, such therapies could be halted during a period of cancer therapy. The tricky part is to administer telomerase in such a way as not to cause cancer. Cancer cells possess a gene that produces telomerase, which effectively enables them to become immortal by reproducing indefinitely. A key cancer-fighting strategy, therefore, involves blocking the ability of cancer cells to generate telomerase. This may seem to contradict the idea of extending the telomeres in normal cells to combat this source of aging, but attacking the telomerase of the cancer cells in an emerging tumor could be done without necessarily compromising an orderly telomere-extending therapy for normal cells. However, to avoid complications, such therapies could be halted during a period of cancer therapy.

Reversing Aging

It is logical to a.s.sume that early in the evolution of our species (and precursors to our species) survival would not have been aided-indeed, it would have been compromised-by individuals living long past their child-rearing years. Recent research, however, supports the so-called grandma hypothesis, which suggests a countereffect. University of Michigan anthropologist Rachel Caspari and University of California at Riverside's San-Hee Lee found evidence that the proportion of humans living to become grandparents (who in primitive societies were often as young as thirty) increased steadily over the past two million years, with a fivefold increase occurring in the Upper Paleolithic era (around thirty thousand years ago). This research has been cited to support the hypothesis that the survival of human societies was aided by grandmothers, who not only a.s.sisted in raising extended families but also pa.s.sed on the acc.u.mulated wisdom of elders. Such effects may be a reasonable interpretation of the data, but the overall increase in longevity also reflects an ongoing trend toward longer life expectancy that continues to this day. Likewise, only a modest number of grandmas (and a few grandpas) would have been needed to account for the societal effects that proponents of this theory have claimed, so the hypothesis does not appreciably challenge the conclusion that genes that supported significant life extension were not selected for.

Aging is not a single process but involves a multiplicity of changes. De Grey describes seven key aging processes that encourage senescence, and he has identified strategies for reversing each one.

DNA Mutations. Generally mutations to nuclear DNA (the DNA in the chromosomes in the nucleus) result in a defective cell that's quickly eliminated or a cell that simply doesn't function optimally. The type of mutation that is of primary concern (as it leads to increased death rates) is one that affects orderly cellular reproduction, resulting in cancer. This means that if we can cure cancer using the strategies described above, nuclear mutations should largely be rendered harmless. De Grey's proposed strategy for cancer is preemptive: it involves using gene therapy to remove from all our cells the genes that cancers need to turn on in order to maintain their telomeres when they divide. This will cause any potential cancer tumors to wither away before they grow large enough to cause harm. Strategies for deleting and suppressing genes are already available and are being rapidly improved. Generally mutations to nuclear DNA (the DNA in the chromosomes in the nucleus) result in a defective cell that's quickly eliminated or a cell that simply doesn't function optimally. The type of mutation that is of primary concern (as it leads to increased death rates) is one that affects orderly cellular reproduction, resulting in cancer. This means that if we can cure cancer using the strategies described above, nuclear mutations should largely be rendered harmless. De Grey's proposed strategy for cancer is preemptive: it involves using gene therapy to remove from all our cells the genes that cancers need to turn on in order to maintain their telomeres when they divide. This will cause any potential cancer tumors to wither away before they grow large enough to cause harm. Strategies for deleting and suppressing genes are already available and are being rapidly improved.

Toxic Cells. Occasionally cells reach a state in which they're not cancerous, but it would still be best for the body if they did not survive. Cell senescence is an example, as is having too many fat cells. In these cases, it is easier to kill these cells than to attempt to revert them to a healthy state. Methods are being developed to target ”suicide genes” to such cells and also to tag these cells in a way that directs the immune system to destroy them. Occasionally cells reach a state in which they're not cancerous, but it would still be best for the body if they did not survive. Cell senescence is an example, as is having too many fat cells. In these cases, it is easier to kill these cells than to attempt to revert them to a healthy state. Methods are being developed to target ”suicide genes” to such cells and also to tag these cells in a way that directs the immune system to destroy them.

Mitochrondrial Mutations. Another aging process is the acc.u.mulation of mutations in the thirteen genes in the mitochondria, the energy factories for the cell. Another aging process is the acc.u.mulation of mutations in the thirteen genes in the mitochondria, the energy factories for the cell.50 These few genes are critical to the efficient functioning of our cells and undergo mutation at a higher rate than genes in the nucleus. Once we master somatic gene therapy, we could put multiple copies of these genes in the cell nucleus, thereby providing redundancy (backup) for such vital genetic information. The mechanism already exists in the cell to allow nucleus-encoded proteins to be imported into the mitochondria, so it is not necessary for these proteins to be produced in the mitochondria themselves. In fact, most of the proteins needed for mitochondrial function are already coded by the nuclear DNA. Researchers have already been successful in transferring mitochondrial genes into the nucleus in cell cultures. These few genes are critical to the efficient functioning of our cells and undergo mutation at a higher rate than genes in the nucleus. Once we master somatic gene therapy, we could put multiple copies of these genes in the cell nucleus, thereby providing redundancy (backup) for such vital genetic information. The mechanism already exists in the cell to allow nucleus-encoded proteins to be imported into the mitochondria, so it is not necessary for these proteins to be produced in the mitochondria themselves. In fact, most of the proteins needed for mitochondrial function are already coded by the nuclear DNA. Researchers have already been successful in transferring mitochondrial genes into the nucleus in cell cultures.

Intracellular Aggregates. Toxins are produced both inside and outside cells. De Grey describes strategies using somatic gene therapy to introduce new genes that will break down what he calls ”intracellular aggregates”-toxins within cells. Proteins have been identified that can destroy virtually any toxin, using bacteria that can digest and destroy dangerous materials ranging from TNT to dioxin. Toxins are produced both inside and outside cells. De Grey describes strategies using somatic gene therapy to introduce new genes that will break down what he calls ”intracellular aggregates”-toxins within cells. Proteins have been identified that can destroy virtually any toxin, using bacteria that can digest and destroy dangerous materials ranging from TNT to dioxin.

A key strategy being pursued by various groups for combating toxic materials outside the cell, including misformed proteins and amyloid plaque (seen in Alzheimer's disease and other degenerative conditions), is to create vaccines that act against their const.i.tuent molecules.51 Although this approach may result in the toxic material's being ingested by immune system cells, we can then use the strategies for combating intracellular aggregates described above to dispose of it. Although this approach may result in the toxic material's being ingested by immune system cells, we can then use the strategies for combating intracellular aggregates described above to dispose of it.

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