Testing Times
Researchers are working on ways to reduce the need for animal experiments, but new laws may increase the number of experiments needed.
The current situation
In an ideal world, people would not perform experiments on animals. For the people, they are expensive. For the animals, they are stressful and often painful.
That ideal world, sadly, is still some way away. People need new drugs and vaccines. They want protection from the toxicity of chemicals. The search for basic scientific answers goes on. Indeed, the European Commission is forging ahead with proposals that will increase the number of animal experiments carried out in the European Union, by requiring toxicity tests on every chemical approved for use within the union’s borders in the past 25 years.
Already, the commission has identified 140,000 chemicals that have not yet been tested. It wants 30,000 of these to be examined right away, and plans to spend between ~ 4 billion — 8 billion ($5 billion—10 billion) doing so. The number of animals used for toxicity testing in Europe will thus, experts reckon, quintuple (翻五倍) from just over lm a year to about 5m, unless they are saved by some dramatic advances in non-animal testing technology. At the moment, roughly 10% of European animal tests are for general toxicity, 35% for basic research, 45% for drugs and vaccines, and the remaining 10% a variety of uses such as diagnosing diseases.
Animal experimentation will therefore be around for some time yet. But the search for substitutes continues, and last weekend the Middle European Society for Alternative Methods to Animal Testing met in Linz, Austria, to review progress.
A good place to start finding alternatives for toxicity tests is the liver--the organ responsible for breaking toxic chemicals down into safer molecules that can then be excreted. Two firms, one large and one small, told the meeting how they were using human liver cells removed incidentally during surgery to test various substances for long-term toxic effects.
One way out of the problem
PrimeCyte, the small firm, grows its cells in cultures over a few weeks and doses them regularly with the substance under investigation. The characteristics of the cells are carefully monitored, to look for changes in their microanatomy.
Pfizer, the big firm, also doses its cultures regularly, but rather than studying individual cells in detail, it counts cell numbers. If the number of cells in a culture changes after a sample is added, that suggests the chemical in question is bad for the liver.
In principle, these techniques could be applied to any chemical. In practice, drugs (and, in the case of PrimeCyte, food supplements) are top of the list. But that might change if the commission has its way: those 140,000 screenings look like a lucrative market, although nobody knows whether the new tests will be ready for use by 2009, when the commission proposes that testing should start.
Other tissues, too, can be tested independently of animals. Epithelix, a small firm in Geneva, has developed an artificial version of the lining of the lungs. According to Huang Song, one of Epithelix’s researchers, the firm’s cultured cells have similar microanatomy to those found in natural lung linings, and respond in the same way to various chemical messengers. Dr. Huang says that they could be used in long-term toxicity tests of airborne chemicals and could also help identify treatments for lung diseases.
The immune system can be mimicked and tested, too. ProBioGen, a company based in Berlin, is developing an artificial human lymph node (淋巴结) which, it reckons, could have pred the neardisastrous consequences of a drag trial held in Britain three months ago, in which (despite the drag having passed animal tests) six men suffered multiple organ failure and nearly died. The drug the men were given made their immune systems hyperactive. Such a response would, the firm’s scientists reckon, nave identified by their lymph node, which is made from cells that provoke the immune system into a response. ProBioGen’s lymph node could thus work better than animal testing.
A second alternative
Another way of cutting the number of animal experiments would be to change the way that vaccines are tested, according to Coenraad Hendriksen of the Netherlands Vaccine Institute. At the moment, all batches of vaccine are subject to the same battery of tests. Dr. Hendriksen argues that this is over-rigorous. When new vaccine cultures are made, belt-and-braces tests obviously need to be applied. But if a batch of vaccine is derived from an existing culture, he suggests that it need be tested only to make sure it is identical to the batch from which it is derived. That would require fewer test animals.
All this suggests that though there is still some way to go before drugs, vaccines and other substances can be tested routinely on cells rather than live animals, useful progress is being made. What is harder to see is how the use of animals might be banished from fundamental research.
Weighing the balance
In basic scientific research, where the object is to understand how, say, the brain works rather than to develop a drug to treat brain disease, the whole animal is often necessarily the object of study. Indeed, in some cases, scientific advances are animal tests more valuable, rather than less. Geneticmodification techniques mean that mice and rats can be remodelled to make them exhibit illnesses that they would not normally suffer from. Also, genes for human proteins can be added to them, so that animal tests will more closely mimic human responses. This offers the opportunity to understand human diseases better, and to screen treatments before human trials begin. However, the very creation of these mutants (突变异种) counts as an animal experiment in its own right, so the number of experiments is increasing once again.
What is bad news for rodents, though, could be good news for primates. Apes and monkeys belong to the same group of mammals as humans, and are thus seen as the best subjects for certain sorts of experiment. To the extent that rodents can be "humanised", the number of primate experiments might be reduced.
Some people, of course, would like to see them eliminated altogether, regardless of the effect on useful research. On June 6th the British Union for the Abolition of Vivisection, an animal-rights group, called for the use of primates in research to be banned. For great apes, this has already happened. Britain, Austria, the Netherlands, New Zealand and Sweden have ended experiments on chimpanzees, gorillas, bonobos and orang-utans. Experiments on monkeys, though, are still permitted. And some countries have not banned experiments on apes. In America, for example, about 1,000 chimpanzees a year are used in research.
This is a difficult area. Great apes are man’s closest relatives, having parted company from the human family tree only a few million years ago. Hence it can be (and is) argued that they are indispensable for certain sorts of research. On the other hand, a recent study by Andrew Knight and his colleagues at Animal Consultants International, an animal-advocacy group, casts doubt on the claim that apes are used only for work of vital importance to humanity. Important papers tend to get cited as references in subsequent studies, so Mr. Knight looked into the number of citations received by 749 scientific papers published as a result of invasive experiments on captive chimpanzees. Half had received not a single citation up to ten years after their original publication.
That is ing. Animal experiments are needed for the advance of medical science, not to mention people’s safety. But if scientists are to keep the sympathy of the public, they need to do better than that. Animal experiments are needed in research to find new drugs and vaccines, and to find ways of protection from the toxicity of chemicals.