Fri, 22 Nov 1996 Eileen Church Director of Communications American Association of Blood BanksI attended the International Conference on Viral Safety of Plasma Derivatives, held on the NIH campus, USA, on Nov 20-22. Friday's program began with a review of transmissible spongiform encephalopathies.
According to Martin Zeidler, National CJD Surveillance Unit, Western General Hospital, Edinburgh, UK, the number of cases of variant CJD in the UK will probably peak in about seven years. He based this estimate on the assumption that infections crossing the species barrier generally have a longer incubation period that intraspecies infections, and on evidence that Kuru infections have an incubation period of about 10 years; growth hormone 12 years. He also claimed to have survey evidence that the people infected with v-CJD in the UK tended to have eaten more beef, particularly beefburgers, than a control population. This was determined by questioning of relatives who may have been biased toward blaming beef, he noted.
Paul Brown, of the National Institute of Neurological Disorders and Stroke (NIH) noted that the agent causing CJD (regular CJD) is one of the most resistant to inactivation the world now knows. Having said that, he noted that it can be rendered completely inactive or nearly inactive by chemical methods (1 N NaOH) or 5 percent NaOC or by autoclaving at at least 132 C for at least an hour. This is a higher autoclaving temp than usual and a longer period. He recommended using both the chemical and autoclaving methods in tandem. He said even at that, he would not be surprised to see breakthrough infectivity. He also noted what is ineffective, including:
-boiling -UV irradiation -Hospital disinfectants -organic solvents (although they can have a small effect) -ethylene oxide -gluteraldehyde -formaldehyde (storage of instruments for five years in formaldehyde did not decrease the infectivity of the agent at all) -urea (6-8 molar) He noted that urea did not affect infectious tissue, but is effective on purified prionsDr. Brown also made the point that dilution does not work in the case of the CJD agent. (This was important to the audience; remember, they are plasma fractionators). For example, if there are 10 infectious units, for another infectious agent, it might be possible to dilute it, lowering the infectivity of the final product to a level the body can handle. Dilution has the opposite effect on the CJD agent, he noted. For example, if there are 10 infectious units, and they are divided into 10 containers, each one becomes infectious. Dr. Brown also said that for the most sensitive test we have for prions, the level of agent needed for it to be detected at all is many thousands of infectious doses.
Dr. Brown is currently working on hamster studies to determine whether blood from other infected hamsters inoculated intracerebrally transmit CJD.
Finally, it was mentioned that many companies are working on methods for detecting and inactivating the CJD agent. Because of the proprietary nature of that info, it was not presented at the meeting. However, one company did distribute a statement saying in part: "Hamosam has developed a process which not only inactivates non-lipid coated viruses like FMD, polio and SV 40 a high titres, but also prions, shown by the removal of >10 exp. 5.8 logs scrapie infectivity during the processing of serum albumin. This HEMOSAFE process can be adapted to treat plasma and serum, immunoglobulins and even enzymes and clotting factors.
First main steps are:
1. Heating in the presence of anionic tensides (and stabilisers) 2. Incubation with chaotropic reagents, which can be included into existing purification schemes without major changes or investments. Contact Herwig Reichl, Hamosan, Graz. Austria, 0043-316-681713.
After spending billions of dollars to slaughter cattle infected with bovine spongiform encephalopathy (BSE)--"mad cow disease"--and compensate farmers for their lost herds, the European Union (EU) has launched a major pan-European research effort into the disease. Last week, the European Commission, the EU's executive arm, announced that it will set aside $63.5 million for the new program, which will focus on a trio of related disorders characterized by spongy degeneration of brain tissue: BSE, Creutzfeldt-Jakob disease in humans, and scrapie in sheep.
European politicians have long been urging the commission to launch such a program. It will closely follow a set of recommendations laid out in a report earlier this year by a scientific panel chaired by Charles Weissmann of the Institute of Molecular Biology at the University of Zurich. It will focus on five priority areas: epidemiological and social studies of these diseases; infectious agents and their transmission; diagnosis; risk assessment; and treatment and prevention.
Neuropathologist Adriano Aguzzi of the University Hospital in Zurich, Switzerland, calls the program "good news." Centralized funding is particularly necessary in the case of BSE research, he says, "because of the need for international infrastructure" to do the costly, long-term animal experiments required to study the infectivity of these diseases. "The areas identified are clearly very practically oriented," adds molecular biologist Chris Bostock of Britain's Institute of Animal Health in Compton, Berkshire. But he cautions that the need for fast fixes "should not be at the expense of basic research." Bostock points out that the Weissmann report emphasizes that "we know very little about these diseases."
This program has been a long time in the making. The European Parliament has called several times for a pan-European research program to tackle the problem of BSE, which has been confirmed in more than 160,000 U.K. cattle, but in no more than a few hundred cattle in other European countries. And in early October, research ministers from the 15 EU member states agreed to go ahead. They even agreed on the size of the program, but they fell out over whether the money should come from the commission's internal budget or from the EU's 1994 to '98 research program, known as Framework IV. A compromise was reached last week in which $20 million would come out of current research funds and the remainder from a separate fund that can be added to this year's Framework budget in special circumstances. Research ministers will gather again on 5 December to give the final go-ahead to the project, and meanwhile finance ministers will be asked to approve the use of the special funds.
Once the program is up and running, the funds will be awarded on a competitive basis, with the division of funds among the five priority areas depending on what projects are approved, rather than an equal split. Aguzzi expects no shortage of proposals. He says that as a referee of grant proposals submitted to the Framework program, he sees many good projects turned away.
"physicians might one day consider delivering so-called antisense or antigene therapies to the brains of patients with prion diseases. Such therapies aim to block genes from giving rise to unwanted proteins and could potentially shut down production of cellular PrP"
Claims by Icelandic researchers that mites found in hay may be able to spread the sheep disease scrapie and mad cow disease are to be investigated by the Ministry of Agriculture. Scientists have speculated that the mites could account for some mysterious outbreaks of BSE.
RESEARCH into "mad cow" disease has revealed the first hard evidence that the experiments the government used to proclaim the safety of British beef were seriously flawed, writes Steve Connor. Scientists at the Ministry of Agriculture, Fisheries and Food found the tests that formed the basis of ministerial assurances on beef were at least 1,000 times less sensitive than alternative tests which are only now being performed.
The findings, which are not yet formally published in the scientific press, are likely to be used by other European Union (EU) countries to support their worldwide ban on beef exports from Britain. EU scientists could argue that the earlier tests may have given a false sense of security about the safety of British beef if their now proven insensitivity failed to detect small amounts of the BSE agent that may be present in muscle tissue.
British scientists emphasised that there is no evidence that BSE has ever been present in the muscle of infected cattle. However, they accept that meat from nearly 800,000 cattle incubating BSE entered the human food chain up to 1995 and that small amounts of the infectious agent may have been eaten.
The new research involved injecting BSE material from the brains of infected cattle into the brains of calves. It was found that the smallest lethal dose was one thousandth of the concentration needed to kill a mouse ‚ the subject of the previous government tests. Dr John Wilesmith, a senior scientist at the government's Central Veterinary Laboratory, will reveal preliminary findings of the study in BBC2's Horizon programme tomorrow night.
A great deal of controversy and concern exists over potential transmission of central nervous system diseases by corneal transplant. The purpose of this study was to evaluate the available data relative to this question, pertaining especially to transmission of infectious dementia. From these data, determination of conveyance risks are possible, and rational policies for donor inclusion criteria can be constructed. Retrospective analysis of available published data regarding transmission of infectious dementias was performed.
Risk of disease transmission was calculated from population data. Of the various forms of dementia, only rabies, hepatitis B, and Creutzfeldt-Jakob disease (CJD) have been transmitted by corneal transplantation. Transmission of the first two viruses is preventable by serologic testing. Prevention of CJD transmission relies on clinical history.
Despite the possibility of transmission and the lack of available testing, slow virus disease (CJD) has been transmitted only once. That this case represents an extremely rare event is supported by a lack of successful transmission via corneal transplant in monkeys; lower levels of infectious agent in cornea than in brain; lack of successful transmission of similar human dementias, including Alzheimer's disease to primates; the apparent requirement for homozygosity at codon 129 of chromosome 20 for transmission; lack of transmission in 5-10% of CJD cases even after brain inoculation; and low numerical risk of transmission based on population data.
Only 0.5-4 CJD infected donors per year would be expected. Current Eye Bank Association of America criteria for donor exclusion based on suspicious history are adequate to protect against accidental conveyance of transmissible dementia.
The prion, the transmissible agent that causes spongiform encephalopathies such as scrapie, bovine spongiform encephalopathy (BSE) and Creutzfeldt-Jakob disease, is believed to be devoid of nucleic acid and identical with PrPSc, a modified form of the normal host protein PrPC which is encoded by the single copy gene Prnp. The 'protein only' hypothesis proposes that PrPSc, when introduced into a normal host, causes the conversion of PrPC into PrPSc; it therefore predicts that an animal devoid of PrPC should be resistant to prion diseases. We generated homozygous Prnp(olo) ('PrP knockout') mice and showed that, after inoculation with prions, they remained free of scrapie for at least 2 years while wild-type controls all died within 6 months. There was no propagation of prions in the Prnp(olo) animals.
Surprisingly, heterozygous Prnp(ol+) mice, which express PrPC at about half the normal level, also showed enhanced resistance to scrapie disease despite high levels of infectious agent and PrPSc in the brain early on. After introduction of murine PrP transgenes Prnp(olo) mice became highly susceptible to mouse but not to hamster prions, while the insertion of Syrian hamster PrP transgenes rendered them susceptible to hamster but to a much lesser extent to mouse prions. These complementation experiments paved the way to the application of reverse genetics. We have prepared animals transgenic for genes encoding PrP with amino terminal deletions of various lengths and have found that PrP lacking 48 amino proximal amino acids, which comprise four of the five octa repeats of PrP, is still biologically active.
WASHINGTON (Nov 19, 1996 10:18 a.m. EST) -- Some rare brain disorders may be caused by "friendly fire" -- the body's attempt to defend itself against invading bacteria and viruses, researchers say. Scientists once considered the brain to be an immunologically privileged area, that is, not susceptible to the constant war under way between the body's immune system and germs. But recent studies have shown that the immune system can confuse normal cells in the brain and the central nervous system with the enemy invaders. When the immune system makes a mistake and attacks these cells, patients can develop bizarre and debilitating neurological disorders, researchers said Monday at the national meeting of the Society for Neuroscience.
Even cancer can cause the body to attack its own nervous system, they said. "The immune system evolved to fight microbes," said Dr. Lawrence Steinman of Stanford University. "But some of the microbes share characteristics of some of the cells in the nervous system." As a result, he said, immune system attack cells can confuse brain or nerve cells with the enemy and mount a powerful attack. Disorders caused by an immune system gone awry are called autoimmune diseases. When such autoimmune attacks strike the brain or nervous system, victims can suddenly lose the ability to coordinate their arms and legs, or develop the rare "stiff-man syndrome" in which every muscle is uncontrollably rigid. In children, autoimmune action can initiate Rasmussen's enchephalitis, a rare type of epilepsy that involves constant and unremitting seizures.
Dr. Jerome Posner of Memorial Sloan-Kettering Cancer Center and Cornell Medical College, said some cancer victims develop neurological disorders because the body is mounting an attack against cancer cells. Some patients have been found to have antibodies that attack not only the cancer, but also the central nervous system, and often the neurological disease appears first, he said.
In some patients, said Posner, surgically removing the cancer has cured the neurological disease because it turns off the immune system attack. Dr. Michele Solimena of Yale University said he has treated patients who develop the stiff-man syndrome, a "very serious disease" that researchers now know can be caused when the immune system attacks brain neurons that control muscles. Despite its name, stiff-man syndrome attacks mostly women, and most of the victims have diabetes or breast or ovarian cancer.
Solimena said studies show that the syndrome is caused when the immune system attacks neurons that produce an enzyme called GAD. This same enzyme is also produced by pancreas cells, further supporting the conclusion that an autoimmune reaction is causing both disorders. Dr. Scott Rogers of the University of Utah said he linked Rasmussen's encephalitis with a flawed immune system attack while researching brain chemistry in rabbits. He said two rabbits developed symptoms like those of the epilepsy when brain cells were exposed to certain antibodies.