Botox could break the pain barrier

Exclusive from New Scientist Print Edition

Combining the most potent neurotoxin known to man and a protein from the Mediterranean coral tree could deliver a long-lasting treatment for the chronic pain that afflicts millions of people, including cancer patients.

The neurotoxin in question is botulinum toxin, perhaps better known as Botox, the treatment that has smoothed out the wrinkles on many a celebrity forehead. But it is also used to treat an increasing range of medical conditions.

The neurotoxin, whose effects can last for months, works by blocking the release of the neurotransmitters that relay the "contract now" message from nerves to muscles. The machinery that is knocked out is actually found inside most cells, but the toxin only affects the neurons that control muscles. This is because of a targeting sequence in the toxin that only permits it to bind to muscle cells.

So Keith Foster's team at the Centre for Applied Microbiology and Research near Salisbury, UK, went looking for a targeting sequence specific to the nerves that transmit pain signals. He wanted to use this sequence to turn the neurotoxin into a painkiller. They found it in the Mediterranean coral tree, Erythrina cristagalli.

It may be a complete coincidence that the coral tree protein binds to the surface of pain neurons and no other cells, but all that matters to Foster is that it does. Since pain nerves do not carry any other sort of message, the altered toxin his team has created stops pain without affecting touch, for example.

Longer lasting

Results from tests in mice have been impressive. In three experiments, Foster's painkiller performed as well as morphine at preventing pain. But it was still working nine days later, whereas morphine would have worn off after four hours.

The team is now preparing for initial trials of the drug, Foster told the Society for General Microbiology meeting in Edinburgh, Scotland, last week. The first people to be treated are likely to be cancer sufferers or patients recovering from surgery. But with as many as one in three people suffering from some kind of chronic pain, the drug could benefit millions if it proves safe and effective.

Adding different targeting sequences could lead to all sorts of other applications, points out Hans Bigalke at Hannover University, an expert on botulinum toxin.

Inhibiting the release of inflammatory mediators might prevent asthma, for example, while disrupting glucose uptake by fat cells could stop them storing fat and so prevent obesity. "We're not short of ideas as to where we could take this," enthuses Foster.

James Randerson, Edinburgh

Genetic sequence of SARS virus revealed

NewScientist.com news service

The full DNA sequence of the coronavirus believed to cause SARS has been published by scientists in Canada, the worst-affected western country. The genetic sequence is vital to developing tests for the infection, and drugs and vaccines to treat it.

The breakthrough comes as the SARS outbreak continues to worsen. It has now killed 143 people and infected over 3400 in many countries around the world. The situation remains very serious in China, where SARS originated, and Hong Kong.

Chinese prime minister Wen Jiabao contradicted earlier government reassurances on Sunday, saying that the "overall situation remains grave", while Hong Kong leader Tung Chee-hwa said SARS had yet to be "brought under effective control".

And David Heymann, head of infectious diseases at the WHO warned on Friday: "If SARS maintains its present pathogenicity and transmissibility, it could become the first severe new disease of the 21st century with global epidemic potential."

Faster tests

The full coronavirus sequence will allow the development of faster, more accurate tests for SARS, using specific viral DNA fragments to prime PCR reactions. Early sequencing by the Bernhard Nocht Institute in Hamburg, Germany, has already helped the German firm Artus to produce a test that goes on sale on Monday.

The sequence will also permit the synthesis of specific viral proteins. These could be used to induce antibodies in healthy people, which can then be used to treat SARS patients.

Ultimately, viral proteins will be the basis of a vaccine. There are also long-term hopes that a detailed understanding of the function of the viral proteins could lead to specific antiviral drugs.

The sequence was produced at the Genome Sciences Centre (GSC) at the British Columbia Cancer Agency in Vancouver. The lab usually studies genetic changes in cancer, but it switched to work 24 hours a day on SARS after virus taken from a case in Toronto was cultured.

Tracking mutations

The Canadian genome was the first to be completed, but four other labs around the world are believed to be close to achieving the same feat. Marco Marra, head of the GSC, said it would be important to compare the sequences, to detect mistakes.

But the comparison could also be important in tracking any possible mutations in the virus's genome as it is transmitted through successive waves of people.

It took GSC just six days to sequence the 30,000 "letters" of the virus's genetic code. The sequence confirms earlier screening results that a loop at the 3' end of the RNA appears identical to one in the Avian Infectious Bronchitis virus, which infects turkeys and chickens.

There are also sequence similarities with Bovine Coronavirus, and with a coronavirus that causes hepatitis in mice. But there are also sequences unlike any other known coronavirus, meaning finding the source of SARS may not be straightforward.

Debora MacKenzie

SARS virus is mutating, fear doctors

NewScientist.com news service

A cluster of SARS patients in Hong Kong with unusual symptoms has prompted concern that the virus causing the disease is mutating. Doctors fear the changes are making the disease more severe.

Scientists in Hong Kong are now urgently sequencing key genes from recently isolated coronaviruses to reveal any changes. New Scientist has learned that the changes in symptoms mirror those already seen when animal coronaviruses have mutated.

Microbiologist Yuen Kwok-yung, at the University of Hong Kong, said on Wednesday that the 300 patients from a SARS hot spot, the Amoy Gardens apartment complex, were more seriously ill than patients who acquired the infection elsewhere.

The Amoy Gardens patients are three times as likely to suffer early diarrhoea, twice as likely to need intensive care and less likely to respond to a cocktail of anti-viral drugs and steroids. Even medical staff who caught the infection from Amoy Gardens patients are more seriously ill, Yuen said.

Gut and lung

The comparison of the symptoms is continuing, says John Tam, a microbiologist at the Chinese University of Hong Kong. "But at the same time we are studying the genetic sequences of the viruses involved in both outbreaks. The presence of a mutation leading to an altered tissue preference of the virus cannot be discounted at the moment," he told New Scientist.

The much higher rate of diarrhoea in Amoy Garden cases supports the idea of an altered tissue preference, meaning a viral strain that can attack the gut as well as the lungs.

This switch mirrors effects seen in several animal coronaviruses. A bovine gut coronavirus, with some genetic sequences similar to the SARS virus, can also cause severe pneumonia in cattle. And in the 1980s, a pig gut coronavirus suddenly mutated into a respiratory infection in pigs.

These switches involved mutations in the viral genes coding for the spike proteins, which form the protruding halo that gives coronaviruses their name. Luis Enjuanes and colleagues at Spain's National Centre for Biotechnology in Madrid have switched the pig virus from a mild respiratory infection to a virulent gut infection solely by changing the spike protein gene. Ominously, the gut form replicated much faster.

Pinning down

So scientists are likely to look for changes to the spike protein gene in the virus infecting Amoy Gardens patients. "It may require a lot of sequence work," Malik Peiris, of Hong Kong University, told New Scientist.

But the complete genetic sequences of two virus samples isolated early in the SARS epidemic, now released by Canadian and US researchers, will make it easier to pin down any subsequent changes.

The fears of viral mutation came as the death toll from SARS reached 161, with nearly 3600 reported infections in countries all over the world. On Wednesday, the World Health Organization officially named the new coronavirus as the cause of SARS, based on work reported by New Scientist on 2 April.

And health officials have expressed further concern about the under-reporting of cases in China, where SARS originated. Officially, the capital Beijing has 40 SARS cases. But, after gaining access to two military hospitals, the WHO's Alan Schnur said: "I would guess the range would be between 100 and 200 probable cases in Beijing." In total, about a thousand people are under observation in the city.

Debora MacKenzie

Adult stem cells tackle multiple sclerosis

NewScientist.com news service

Treatment with adult stem cells has cured mice suffering with a form of multiple sclerosis, say Italian researchers. Almost a third of the mice recovered completely from paralysis of their back legs, and the rest all showed substantial improvement.

"It was amazing," says Angelo Vescovi, of the San Raffaele Hospital in Milan. He has now begun experiments giving human adult stem cells to monkeys with the nerve and brain damage seen in MS. But he warns that success in mice does not guarantee success in humans: "I wouldn't want to raise expectations."

Vescovi, Gianvito Martino and colleagues injected the diseased mice with stem cells that had been extracted from the brains of adult mice and multiplied in the lab. The cells were injected in the bloodstream or spinal cord.

Postmortems on the mice showed that the stem cells had migrated to and then repaired damaged areas of the nerves and brain. In particular, the myelin sheaths of nerve cells were restored, after having been worn away.

Seek and repair

Demonstrating that stem cells can locate and repair a multitude of damaged sites by themselves is highly significant for the treatment of MS. "The problem with MS is that we don't know where the lesions are," says Vescovi.

Vescovi stresses that his team's apparent success with adult stem cells should not used as a reason to halt research on embryonic stem cells. Pro-life groups object to research on ESCs because this involves the destruction of embryos aged up to 14 days. These groups argue that adult stem cells are just as promising for medical research.

Although Vescovi does not think embryos should created solely to supply stem cells, he believes it is justified to extract them from spare IVF embryos that would otherwise be "put down the sink".

The European parliament last week voted for draconian new laws to restrict research on embryonic stem cells and on cloning of cells to create tissues for transplant. But the most restrictive measures could be removed as the proposed laws pass through subsequent stages of the legislative process.

Journal reference: Nature (vol 422, p 688)

Andy Coghlan

Final human genome sequence released

NewScientist.com news service

This time it is the real thing, scientists promise - the complete sequence of human DNA, as perfectly rendered as it ever will be.

Much publicity was given to the announcements of the draft human genome, and then its formal publication, but the final version will be officially launched on Monday in Washington DC.

"What we've got now is what we'll have for all eternity," says Francis Collins, director of the US National Human Genome Research Institute and the head of the consortium of 16 international institutions that collaborated to sequence the code.

Now, there are no substantial holes left in the string of three billion base units that make up our chromosomes and determine our biology. There are still parts that are technically unsequenceable, says Collins, "but it's only about 1.5 per cent. That's what we called the finishing line when we began this enterprise, and now we've actually done it."

Highly polished

The largest single contributor to the project was the UK's Wellcome Trust Sanger Institute, which carried out nearly one-third of the work. Its director, Allan Bradley, says: "Completing the human genome is a vital step on a long road but the eventual health benefits could be phenomenal.

"Just one part of this work - the sequencing of chromosome 20 - has already accelerated the search for genes involved in diabetes, leukaemia and childhood eczema," he notes.

Jane Rogers, head of sequencing at the Sanger Institute says: "The working draft allowed researchers to kick-start a multitude of biomedical projects. Now they have a highly polished end product, which will assist them even more. It's a bit like moving from a first-attempt demo music tape to a classic CD."

The raw sequence is freely available on the web. But researchers will have to wait up to a year for the first analysis of it. "We're still discussing the timing on this," Collins says. A broad analysis could be published, or detailed chromosome-by-chromosome papers could be released.

In a forward-looking article to be published in Nature on Thursday, Collins says that as analyses roll in of our genes and the proteins they produce, we need to avoid the patenting controversies that dogged the task of sequencing. "We may be headed for a re-run if we're not careful, and this time we need to be more pro-active" in pre-empting trouble, he says.

Andy Coghlan

'Safe' lead levels still damage children's IQ

NewScientist.com news service

Even exposure to "safe" amounts of lead damages children's intelligence, reveals a new study. In fact, lead's effect on intelligence is proportionately greater at low blood levels, meaning most of the damage is caused before the maximum level is reached.

"Our study shows there is no discernible threshold for the adverse effects of lead exposure," says Bruce Lanphear, a pediatrician at the Children's Hospital Medical Center in Cincinnati, Ohio.

The World Health Organization and the US Centers for Disease Control both say blood levels above 10 micrograms of lead per deciliter of blood put children at risk of cognitive damage.

But the new research shows that children with levels at that limit also suffer significant intelligence loss. Children with blood lead levels of 10 micrograms/deciliter had IQs that were 7.4 points lower than children with levels of 1 micrograms/deciliter. When the levels rose from 10 to 30 micrograms/deciliter, intelligence dropped by only another 2.4 IQ points.

Paint and pipes

Children in North America and the UK are exposed to lead mostly through old paint and lead water pipes. The CDC says only two per cent of US children under five years old exceed the WHO/CDC lead limit, but 10 per cent have levels between 5.0 and 10 micrograms/deciliter or higher.

"I think it's an excellent study. I don't think we can say there is a safe level of exposure," says David Bellinger, a neurologist at Harvard Medical School, and a member of the CDC Advisory Committee on Childhood Lead Poisoning Prevention.

Researchers tested lead levels in children from six months to five years of age, and tested their intelligence at three and five years. They adjusted for factors like household income and maternal intelligence and education.

It is not clear why damage should be proportionately greater at lower exposure levels. Lanphear speculates that cells may develop protective mechanisms once lead exposure reaches a certain level.

Journal reference: New England Journal of Medicine (vol 348, p 1517)

Kurt Kleiner

Atherosclerosis Associated With Venous Thrombosis

NEW YORK (Reuters Health) Apr 09 - Results of a case-control study reveal a previously unknown association between atherosclerosis and spontaneous venous thrombosis of the legs.

"Atherosclerosis may induce venous thrombosis, or the two conditions may share common risk factors," investigators suggest in the April 10th issue of The New England Journal of Medicine.

Dr. Paolo Prandoni from the University of Padua in Italy and colleagues performed carotid-artery ultrasonography in 299 patients with acute spontaneous deep venous thrombosis or thrombosis secondary to acquired risk factors but without symptomatic atherosclerosis and in 150 controls.

"The prevalence of carotid plaque was significantly higher in patients with unexplained thrombotic events (47.1%) than in those with secondary ones (27.4%) or in age- and sex-matched subjects without thrombosis (32.0%)," the team reports.

Patients with spontaneous thrombosis had an odds ratio for carotid plaque of 2.3. The odds ratio for carotid plaque in patients with secondary thrombosis and controls was 1.8. The strength of the association held in analyses adjusted for risk factors for atherosclerosis.

Although these results "do not establish a causative role of atherosclerosis in venous thromboembolism, they suggest existence of a link between arterial and venous disorders, which opens important new avenues for further research, including the potential role of statins and antiplatelet agents as preventive interventions," the investigators conclude.

West Nile Virus Can Mimic Other Neurologic Diseases

Charlene Laino

April 4, 2003 (Honolulu) — As mosquito season approaches, physicians need to be aware of atypical presentations of West Nile virus, say researchers who have linked the syndrome to focal neurologic deficits and acute poliomyelitis. They presented their findings here at the American Academy of Neurology 55th annual meeting.

"The symptoms can mimic those of other neurological diseases such as Parkinson's disease, polio, and Guillain-Barre syndrome," said Nidhi Watson, MD, a resident in neurological sciences at Rush-Presbyterian–St. Luke's Medical Center in Chicago, Illinois. "Moreover, many West Nile patients may not have an overt meningitis or encephalitis syndrome as would be expected.

"It can look like another disease but if it's the summer months, physicians need to think about West Nile in the differential diagnosis," Dr. Watson told a press conference.

Dr. Watson and researchers at two other Chicago-area hospitals came to their conclusions after performing a retrospective study of 28 patients. The patients, whose average age was 58 years, all had West Nile virus IgM detected in their serum and/or their cerebrospinal fluid by an IgM-antibody enzyme-linked immunosorbent assay between August and October 2002.

Fifteen patients (54%) had a focal neurologic deficit when first evaluated by a physician, and 40% of these cases presented without symptoms of meningitis or encephalitis, Dr. Watson reported.

The patients suffered from a wide variety of focal deficits, including visual loss, flaccid monoplegia, hemiparesis, bradykinesia, parkinsonian-type tremor with rigidity, bilateral abducens palsies, bilateral facial nerve palsies, focal polyradiculopathy, ataxia or dysmetria, acute motor polyneuropathies, acute sensory polyneuropathies, and acute motor-sensory polyneuropathies, she said. Specific abnormalities on magnetic resonance imaging were seen in only one case.

The focal neurologic deficits developed 3 to 21 days following the onset of fever, Dr. Watson said. "This means that if you had a patient come in with a fever a few weeks ago and now has symptoms such as visual loss, but you can't figure out why, it could be West Nile," she said. "The neurological problem can be delayed two or three weeks."

Two of the patients, both of whom had focal deficits on presentation, died.

Of the 13 patients who did not have focal deficits, 15% had West Nile fever without any neurologic signs and symptoms, and the other 85% had meningitis or encephalitis, she said.

Dr. Watson stressed that most people bitten by an infected mosquito won't become ill and that most people who do become ill recover within a few days. About 20% develop West Nile fever, and less than 1% develop a more severe illness accompanied by encephalitis or meningitis, she said.

Illinois had the nation's highest West Nile virus toll last year with 884 reported cases and 62 deaths. Nationwide, there were 4,161 cases and 277 deaths.

In a different session at the meeting, Jonathan Fratkin, MD, presented additional evidence that West Nile virus can cause poliomyelitis.

"As we head into another season, physicians and other healthcare workers in areas with active West Nile transmission should be aware that muscle weakness and acute flaccid paralysis could be a manifestation of West Nile virus poliomyelitis," said Dr. Fratkin, an associate professor of neurology at the University of Mississippi Medical Center in Jackson. The differential diagnosis can be difficult, he said, because the symptoms mimic those of Guillain-Barre syndrome.

Dr. Fratkin reported on four cases with confirmed West Nile virus infection on whom his team conducted postmortem examinations.

Clinical presentations were similar in all four cases, he said, and included fever, chills, muscle weakness, and acute respiratory distress requiring endotrachial intubation or tracheostomy. The pathological process in all the patients was characteristic of viral infection involving gray matter neurons, he said. "This suggests acute poliomyelitis as a possible cause for the muscle weakness and acute flaccid paralysis."

The major central nervous system finding in all four cases at autopsy was inflammation of the spinal cord gray matter, he said. The lesions included perivascular cuffs of chronic inflammatory cells, including abundant histiocytes and microglial cells, patchy gliosis and neuronal dropout in the ventral gray matter. Additionally, inflammatory cells were bunched around dying anterior horn cells, Dr. Fratkin said. None of the patients showed changes in the hippocampus, cerebral cortex, or cerebellar cortex typical of a hypoxic/ischemic event, he said.

Lara Jeha, MD, who presented a plenary talk on West Nile at the meeting, agreed physicians need to be on the lookout for atypical presentations.

"We now know West Nile can cause symptoms that we didn't think of before last season," said Dr. Jeha, a neurology resident at the Cleveland Clinic in Ohio. "We used to think meningitis and encephalitis, with fever, headache, and confusion. We really didn't think of West Nile presenting as a paralyzed limb — with or without an association with confusion and headache.

"After last year, we know the virus can cause focal neurological deficits and a polio-like presentation, which is itself a type of focal deficit — loss of motor function in a limb," she said.

Now that physicians are aware West Nile virus can cause a polio-like syndrome, Dr. Jeha stressed that it will be important to follow these patients long term to determine if they develop a post-polio-like syndrome.

"We would expect this since we're seeing it in polio patients," she said. "We need to keep our eye out."

AAN 55th Annual Meeting: Abstracts S16.003, S16.005. Presented April 1, 2003.

Reviewed by Gary D. Vogin, MD