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
prevented 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 teen 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
making 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 damning.
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. Recently, an animal-advocacy group casts doubt on the scientists’ claim that apes are used only for