Squirrel monkeys (Saimiri sciureus) infected with the agent of bovine spongiform encephalopathy develop tau pathology

Squirrel monkeys (Saimiri sciureus) were infected experimentally with the agent of classical bovine spongiform encephalopathy (BSE). Two to four years later, six of the monkeys developed alterations in interactive behaviour and cognition and other neurological signs typical of transmissible spongiform encephalopathy (TSE). At necropsy examination, the brains from all of the monkeys showed pathological changes similar to those described in variant Creutzfeldt-Jakob disease (vCJD) of man, except that the squirrel monkey brains contained no PrP-amyloid plaques typical of that disease. Constant neuropathological features included spongiform degeneration, gliosis, deposition of abnormal prion protein (PrP(TSE)) and many deposits of abnormally phosphorylated tau protein (p-Tau) in several areas of the cerebrum and cerebellum. Western blots showed large amounts of proteinase K-resistant prion protein in the central nervous system. The striking absence of PrP plaques (prominent in brains of cynomolgus macaques [Macaca fascicularis] with experimentally-induced BSE and vCJD and in human patients with vCJD) reinforces the conclusion that the host plays a major role in determining the neuropathology of TSEs. Results of this study suggest that p-Tau, found in the brains of all BSE-infected monkeys, might play a role in the pathogenesis of TSEs. Whether p-Tau contributes to development of disease or appears as a secondary change late in the course of illness remains to be determined.

Cumulative costs of inadvertent excess prescribing on multiple item prescription forms

Prescription forms listing more than one item, ie, multiple item prescriptions, may be termed non equivalent if the number of days' treatment prescribed for each of the drugs is different. Patients presenting such prescriptions at 15 community pharmacies were identified and records maintained of all prescriptions presented by these patients over a nine month period. The total amounts of drugs and number of days' treatment prescribed were identified and costed. A total of 53.5 per cent of the non-equivalent items were for amounts representing between one and five days' excess treatment. Excess treatment represented 13.9 per cent of the total cost of these prescriptions. The estimated national cost of inadvertent excess prescribing for 1991/92, based on a projected calculation, was £60m (2.4 per cent of the total expenditure).

Multiplex PCR for detection of Enterobacteriaceae in blood

BACKGROUND

Rapid and sensitive methods are needed to detect the small numbers of bacteria that may sometimes contaminate units of blood during collection. A multiplex 5'-nuclease TaqMan PCR assay (PE Applied Biosystems) was used to detect several bacterial species that may contaminate blood.

STUDY DESIGN AND METHODS

Oligonucleotide primers were made for regions of the 16S rRNA gene conserved in four different bacterial species: Yersinia enterocolitica and Serratia, Klebsiella, and Enterobacter species. Two probes were designed: SL-1 detected Serratia, Klebsiella, and Enterobacter species, and YE-3 detected Y. enterocolitica.

RESULTS

When TaqMan PCR was performed with chromosomal DNA isolated from pure cultures of Serratia liquefaciens, Klebsiella oxytoca, Klebsiella pneumoniae, Enterobacter cloacae, and Enterobacter agglomerans, the limit of detection with probe SL-1 was 1 to 2 CFUs. For S. marcescens, the sensitivity was 8 CFUs. The limit of detection for Y. enterocolitica with probe YE-3 was 2 CFUs. When total chromosomal DNA was extracted from whole-blood samples spiked with different numbers of Y. enterocolitica, S. liquefaciens, E. cloacae, or K. pneumoniae bacteria, the TaqMan PCR detected 12 to 16 organisms in 1 mL of blood.

CONCLUSION

The 5'-nuclease TaqMan PCR assay takes only 3 hours to perform and has the potential to detect very small numbers of bacteria.

Bovine spongiform encephalopathy and variant Creutzfeldt-Jakob disease: background, evolution, and current concerns

The epidemic of bovine spongiform encephalopathy (BSE) in the United Kingdom, which began in 1986 and has affected nearly 200,000 cattle, is waning to a conclusion, but leaves in its wake an outbreak of human Creutzfeldt-Jakob disease, most probably resulting from the consumption of beef products contaminated by central nervous system tissue. Although averaging only 10-15 cases a year since its first appearance in 1994, its future magnitude and geographic distribution (in countries that have imported infected British cattle or cattle products, or have endogenous BSE) cannot yet be predicted. The possibility that large numbers of apparently healthy persons might be incubating the disease raises concerns about iatrogenic transmissions through instrumentation (surgery and medical diagnostic procedures) and blood and organ donations. Government agencies in many countries continue to implement new measures to minimize this risk.

American Academy of Pediatrics. Technical report: transmissible spongiform encephalopathies: A review for pediatricians. Committee on Infectious Diseases

Transmissible spongiform encephalopathies (TSEs) are a family of rare, slowly progressive, and universally fatal neurodegenerative syndromes affecting animals and humans. Until recently, TSEs were of little interest to pediatricians. However, since the outbreak in adolescents and the association of TSEs with new-variant Creutzfeldt-Jakob disease (nvCJD), interest among pediatricians and the general public has increased. Even before bovine spongiform encephalopathy and nvCJD were linked, the recognition that iatrogenic Creutzfeldt-Jakob disease (CJD) had been acquired from administration of cadaveric human growth and gonadotropic hormones and from corneal and dura mater transplants prompted medical vigilance. Furthermore, recent concern about the potential for transmission of CJD by blood and blood products has raised awareness among public health and regulatory agencies, pediatricians, and the public, although no epidemiologic data support this concern. Because of worldwide concern (although no cases have been reported in North America), this review focuses on the potential impact of TSEs, particularly CJD and nvCJD, on the pediatric population.

The transmissible spongiform encephalopathy agents: concerns and responses of United States regulatory agencies in maintaining the safety of biologics

Regulatory agencies responsible for protecting public health must be concerned with reducing or preventing opportunities for exposure of humans and animals to the agents of transmissible spongiform encephalopathies (TSEs), especially bovine spongiform encephalopathy and Creutzfeldt-Jakob disease. The United States Food and Drug Administration (FDA) has taken precautionary actions to assure that regulated products are free of such infectious agents, from both animal and human sources, including the issuing of a regulation and a number of guidance documents. With regard to TSEs, the materials of greatest concern to FDA's Center for Biologics Evaluation and Research have been bovine gelatin, tallow derivatives and serum, as well as human-derived products and excipients including blood, blood components and plasma derivatives. A number of newer issues regarding TSEs now confront agencies responsible for protecting public health. It would be of great help to have standard reference materials available to assist in the diagnosis of the diseases and to detect the infectious agents.

Bovine sera used in the manufacture of biologicals: current concerns and policies of the U.S. Food and Drug Administration regarding the transmissible spongiform encephalopathies

Background

Bovine spongiform encephalopathy (BSE), a member of the transmissible spongiform encephalopathies (TSE), primarily affects cattle. Transmission is via concentrate feed rations contaminated with infected meat and bone meal (MBM). In addition to cattle, other food animal species are susceptible to BSE and also pose a potential threat to human health as consumption of infected meat products is the cause of variant Creutzfeldt-Jakob disease in humans, which is invariably fatal. In the UK, farmed and free ranging deer were almost certainly exposed to BSE infected MBM in proprietary feeds prior to legislation banning its inclusion. Therefore, although BSE has never been diagnosed in any deer species, a possible risk to human health remains via ingestion of cervine products. Chronic wasting disease (CWD), also a TSE, naturally infects several cervid species in North America and is spreading rapidly in both captive and free-ranging populations.

Results

Here we show that European red deer (Cervus elaphus elaphus) are susceptible to intra-cerebral (i/c) challenge with BSE positive cattle brain pool material resulting in clinical neurological disease and weight loss by 794–1290 days and the clinical signs are indistinguishable to those reported in deer with CWD. Spongiform changes typical of TSE infections were present in brain and accumulation of the disease-associated abnormal prion protein (PrP^d) was present in the central and peripheral nervous systems, but not in lymphoid or other tissues. Western immunoblot analysis of brain material showed a similar glycosylation pattern to that of BSE derived from infected cattle and experimentally infected sheep with respect to protease-resistant PrP isoforms. However, the di-, mono- and unglycosylated bands migrated significantly (p < 0.001) further in the samples from the clinically affected deer when compared to BSE infected brains of cattle and sheep.

Conclusion

This study shows that deer are susceptible to BSE by intra-cerebral inoculation and display clinical signs and vacuolar pathology that are similar to those of CWD. These findings highlight the importance of preventing the spread to Europe of CWD from North America as this may necessitate even more extensive testing of animal tissues destined for human consumption within the EU. Although the absence of PrP^d in lymphoid and other non-neurological tissues potentially limits the risk of transmission to humans, the replication of TSE agents in peripheral tissues following intra-cerebral challenge is often limited. Thus the assessment of risk posed by cervine BSE as a human pathogen or for environmental contamination should await the outcome of ongoing oral challenge experiments.

Bovine sera used in the manufacture of biologicals: current concerns and policies of the U.S. Food and Drug Administration regarding the transmissible spongiform encephalopathies

Since 1993, consistent with its statutory responsibility to ensure that regulated products are safe, pure, and free of << extraneous organisms, >> the United States Food and Drug Administration (FDA) has requested that, with certain exceptions, bovine-derived materials from animals born in or residing in countries where bovine spongiform encephalopathy has occurred, should not be used to manufacture products intended for humans. FDA's Center for Biologics Evaluation and Research (CBER) has specifically recommended that serum used to produce biologicals be obtained from sources << certified to be free from contaminants and adventitious agents, such as the agent responsible for the production of Bovine Spongiform Encephalopathy. >> The United States Department of Agriculture (USDA) has prohibited importation of such serum for use in products. FDA staff are aware that bovine blood, including foetal blood, and placental tissues and fluids that might contaminate foetal serum have not been found to contain the infectious agent of BSE, and that those tissues are considered by most authorities to have little risk for transmitting disease to humans or animals. However, studies of BSE have been limited in size and sensitivity, and several experimental studies of scrapie and CJD in rodents found their blood to be infectious. In addition, a recent unpublished study of BSE (requiring confirmation) reported finding infectivity in the bone marrow of cattle. Possible transmission of BSE from cows to calves, although unlikely to constitute a major mode for maintaining the BSE outbreak, has also not been rigorously ruled out. Considering the special nature of biological products, especially of vaccines intended for widespread use in children, it seems prudent for U.S. regulatory authorities to continue current conservative policies that discourage or prohibit the use of bovine serum from countries with BSE.

Mutations in Sabin 2 strain of poliovirus and stability of attenuation phenotype

In this study, we attempted to identify the molecular determinants in the genome of the attenuated Sabin 2 vaccine strain of poliovirus that may change during vaccine production and result in an increase in monkey neurovirulence. An extensive search for suitable vaccine lots identified six batches that had failed the monkey neurovirulence test (MNVT). On repeated tests, these batches were found to have acceptable levels of monkey neurovirulence. One of the batches was additionally passaged six times under conditions used in vaccine production, and the resulting high-passage sample was screened for the presence of mutations and tested in monkeys. In addition to the previously described A --> G reversion at nucleotide 481, high-passage stock also contained a mutation in the VP1-coding region (3364 = G --> A) that consistently accumulated in the course of passaging. However, despite the presence of substantial amounts of these mutations, high-passage stock passed the MNVT. Replication of Sabin 2 poliovirus in the central nervous system of transgenic mice susceptible to poliovirus or in cultures of mouse cells, resulted in another mutation (3363 = A --> G). Even though its presence correlated with paralysis in mice, the introduction of 3363-G into the Sabin 2 genome did not increase neurovirulence of the virus. Previous studies identified the 481-G mutation as an important determinant of monkey neurovirulence. We prepared virus samples with varying amounts of genetically defined single mutants at this nucleotide and tested them in monkeys. The results demonstrated that even a 100% substitution at this site introduced into Sabin 2 strain did not increase monkey neurovirulence. The determination of the nucleotide sequence of an alternative strain used for the production of type 2 OPV (Chung 2) showed that it contained 100% of the wild-type 481-G but possessed an extremely low level of neurovirulence. These results demonstrate the remarkable stability of the attenuated phenotype of the Sabin 2 strain and show that (1) no batch of OPV 2 has ever repeatedly failed the MNVT, (2) growing the virus beyond the passage level allowed in vaccine production did not result in increased neurovirulence in monkeys, (3) a test for neurovirulence in transgenic mice may be more sensitive than the MNVT, and (4) determination of the mutational profile of vaccine batches detects inconsistencies in vaccine manufacturing processing that would not be detected by the MNVT.

Oral iodine supplementation does not reduce neutralizing antibody responses to oral poliovirus vaccine

Iodine deficiency is a major cause of impaired mental development, goitre, and cretinism in many parts of the world. Because existing immunization programmes can be used to deliver oral iodized oil (OIO) to infants at risk, it was important to know whether OIO could adversely affect the antibody response to vaccines, such as trivalent oral poliovirus vaccine (OPV). A randomized, double-blind, placebo-controlled clinical trial was conducted in Subang, West Java, Indonesia, in which 617 eight-week-old infants received either OIO or a placebo (poppy-seed oil) during a routine visit for their first dose of OPV as part of the Expanded Programme on Immunization (EPI). The infants received two boosters of OPV at 4-week intervals after the first dose, and were followed up when 6 months old. Neutralizing antibody titres to poliovirus serotypes 1, 2, and 3 were compared in serum samples that were taken from 478 of these infants just before the first dose of OPV and at 6 months. It was found that oral iodized oil did not reduce the antibody responses to any of the three serotypes of OPV. These results indicate that oral iodine may safely be delivered to infants at the same time as oral poliovirus vaccine according to current EPI immunization schedules.

Genetic stability of Sabin 1 strain of poliovirus: implications for quality control of oral poliovirus vaccine

The Sabin vaccine strains of poliovirus, like all RNA viruses, exist as a quasispecies of genomic sequences whose composition can be altered during virus propagation. Since changes in vaccine virus during manufacture can enhance the neurovirulent potential of the vaccine, each monovalent lot of oral poliovirus vaccine (OPV) undergoes several tests to ensure consistency of manufacture, including the monkey neurovirulence test (MNVT). Recently, we proposed a new molecular approach for direct quantification of vaccine variants with neurovirulent potential as an alternative way to monitor consistency of OPV production. Analysis of the Sabin 1 genome allowed us to identify a limited number of specific loci that exhibit significant change during viral propagation in vitro and in vivo. Here we explore the possible roles of these changes and show that 7427-U-->C and 7441-G-->A alterations in the 3'-UTR of the Sabin 1 virus do not increase monkey neurovirulence. These, as well as our previous results, suggest that only mutations in the 5'-UTR play a significant role in the limited increase in Sabin 1 monkey neurovirulence observed after extended propagation of the virus beyond the passage level used in vaccine production. Our studies with high-passage batches of the Sabin 1 strain confirmed the stability of this strain, which retains acceptable levels of monkey neurovirulence even after serial passages at elevated temperature. Compared to the MNVT, molecular analysis of the genetic composition of Sabin 1 poliovirus provides a more sensitive analytical approach to monitor consistency of vaccine production.

Viliuisk encephalomyelitis--review of the spectrum of pathological changes

Viliuisk encephalomyelitis (VE) is an unique neurological disease occurring in the Iakut (Sakha) people of Siberia. Evolution of the disease follows one of three broad clinical forms: subacute, slowly progressive or chronic. Death occurs within 3 to 6 months in subacute cases and within 6 years in the slowly progressive cases. Chronic cases lack a subacute phase but show a slowly progressive dementia associated with bradykinesia, dysarthria and spastic paraparesis that stabilizes late in the disease process. In subacute and slowly progressive cases, focal necrotizing encephalomyelitis is seen at necropsy. Chronic cases show multifocal areas of lysis with a gliotic margin, predominantly within grey matter, lacking associated chronic inflammatory changes seen in the other forms of the disease. Epidemiological studies are consistent with a disease of low-grade communicability, but laboratory studies have so far failed to reveal an infectious organism. The spectrum of neuropathological changes are reviewed in this examination of 11 cases. Although the aetiology of VE remains obscure, further studies are warranted since it may represent a novel disease process.

Inactivated poliovirus vaccine protects transgenic poliovirus receptor mice against type 3 poliovirus challenge

Transgenic (Tg) mice expressing the human poliovirus receptor (PVR) were vaccinated with inactivated poliovirus vaccine (IPV) and evaluated for induced immunity against type 3 poliomyelitis. One injection of monovalent type 3 IPV elicited protective immunity against wild-type poliovirus. In contrast, 2 injections of trivalent IPV were required for protection. Neutralizing antibody response and protection were vaccine dose-dependent. Administration of polio-immune mouse plasma protected unimmunized mice, demonstrating that neutralizing antibody was sufficient for immunity. IPV heated to remove its D antigen component did not induce protection in Tg PVR mice. IPV derived from a wild-type poliovirus strain gave better protection against wild-type viral challenge than IPV derived from an attenuated poliovirus strain. The newly developed Tg PVR mouse-protection test may be useful in evaluating existing IPV potency tests and for attempts to improve formulations of trivalent IPV or combined vaccines for childhood immunization schedules.

Succession of mutations in the Sabin strain of type 3 poliovirus replicating in the central nervous system of monkeys

Sabin strains of oral poliovirus vaccine (OPV) undergo limited genetic changes during replication in cell cultures, the gastrointestinal tract of vaccinees, and the central nervous system of monkeys. Some of these changes are associated with loss of attenuation markers. Here we report the dynamics of mutant accumulation in the Sabin strain of poliovirus type 3 inoculated intraspinally into monkeys. Thr --> lle reversion in amino acid 6 of VP1 (2493 C --> U) occurred within the first few days postinoculation (p.i.), but decreased on later days and completely disappeared by Day 17 p.i. 472 U --> C reversion in the 5'-untranslated region appeared to accumulate slower and by Day 17 completely substituted for the vaccine-type nucleotide at this site. These results indicate that experimental infection of the central nervous system of monkeys consists of early and late phases in which a different genetic constitution of the virus is favored. In several isolates one additional neurovirulent revertant was found: a Phe --> Ser at amino acid 91 of VP3 (2034 U --> C). Since this mutation was never detected in vaccine lots and is strongly selected against in cell cultures at temperatures below 38.5 degrees, it does not threaten the safety of OPV.

Limited genetic changes in the Sabin 1 strain of poliovirus occurring in the central nervous system of monkeys

Replication of attenuated poliovirus strains results in their partial deattenuation. Recently we identified mutations accumulating in the Sabin 1 poliovirus in cell cultures. Here we report genetic changes occurring in this virus during replication in the central nervous system (CNS) of monkeys. Viruses isolated from different parts of the CNS of rhesus monkeys (inoculated into the spinal cord) were screened for sequence heterogeneities and newly identified mutations were independently confirmed and quantified using mutant analysis by PCR and restriction enzyme cleavage (MAPREC). All consistently accumulating mutations identified in this study were located in untranslated regions: GU-->AU or GU-->GC substitution at a complementary pair formed by nucleotides 480 and 525, U-->C substitution at nucleotide 612, and GU-->AU or GU-->GC substitution of a base pair formed by the nucleotides 7427/7441 immediately preceding the poly(A) tract. All these mutations except one (7427) were previously identified in cell culture passages or stool isolates from vaccinees. Sequencing of 11 CNS isolates also identified a few random silent mutations that accumulated as neutral 'passengers', passively co-selected with genuinely selectable mutations present on the same RNA molecule. One isolate also contained the wild-type base at nucleotide 2741 (Ala88-->Thr in VP1). Our results demonstrate a remarkable genetic stability of the Sabin 1 poliovirus in the CNS of monkeys, suggesting that deattenuation is determined by a very limited number of mutations. These mutations can be assayed by MAPREC to monitor the consistency of oral poliovirus vaccine (OPV) production.

Widespread, restricted low-level measles virus infection of brain in a case of subacute sclerosing panencephalitis

In situ reverse transcriptase-polymerase chain reaction amplification with labeled-probe hybridization (in situ RT-PCR/LPH) was used to detect measles virus RNA within formalin-fixed, paraffin-embedded brain tissue sections from a patient who died with subacute sclerosing panencephalitis (SSPE). Many more infected neurons and oligodendrocytes were detected by in situ RT-PCR/LPH than by immunohistochemistry or by in situ hybridization alone. In addition, infection of vascular endothelial cells was demonstrated only by in situ RT-PCR/LPH. The observation that many cells contained only a few copies of viral RNA without detectable antigen is consistent with a persistent viral infection of the central nervous system. In situ RT-PCR/LPH, combining the sensitivity of PCR with the tissue localization of in situ hybridization, should prove useful in further studies to detect nucleic acids in situ in the central nervous system.

Search for viral nucleic acid sequences in brain tissues of patients with schizophrenia using nested polymerase chain reaction

BACKGROUND

We used polymerase chain reaction to search for nucleic acid sequences of several viruses in DNA and RNA extracted from brain tissues of schizophrenic and control subjects.

METHODS

We extracted DNA and RNA templates from frozen brain specimens of 31 patients with schizophrenia and 23 nonschizophrenic control patients with other diseases. The extracts were subjected to polymerase chain reaction with oligonucleotide primers for 12 different viruses (cytomegalovirus, Epstein-Barr virus, herpes simplex virus type 1, human herpesvirus type 6, varicellazoster virus, measles virus, mumps virus, rubella virus, the picornavirus group, influenza A virus, human T-cell lymphotropic virus type I, and St Louis encephalitis virus), several of which have been suspected of involvement in schizophrenia. Nested primers were used to increase the sensitivity of the method.

RESULTS

No amplified nucleic acid sequences encoded by the selected viral genomes were detected in extracts of any brain specimens from either schizophrenic or control patients.

CONCLUSIONS

These data agree with previous studies that failed to find sequences of a number of viruses in the cerebrospinal fluid or selected areas of the brains of schizophrenic patients. Additional efforts should be undertaken to identify other known and unknown pathogens in schizophrenia, sampling more areas of the brain from subjects with a variety of clinical types of schizophrenia.

Low-incidence latent infection with variant B or roseola type human herpesvirus 6 in leukocytes of healthy adults

Nested primer-based polymerase chain reaction was employed to determine the frequency of latent infection with human herpesvirus 6 (HHV-6) among healthy adults from Bratislava, Slovak Republic. A 592-bp region, upstream from the gene encoding the putative large tegument protein of HHV-6, was amplified from DNA extracted from peripheral blood mononuclear cells (PBMC) of only one of 29 seropositive adults, suggesting that as few as 1 in 10(5) PBMC may be infected with the virus. Direct sequencing of the 592-bp fragment indicated that the virus harbored by the seropositive Slovak subject (designated B38) differed by only 3 nucleotides from an HHV-6 variant B strain (R-147) isolated from an American infant with a roseola-like illness and by 32 bases from the variant A strain GS isolated from a patient with lymphadenopathy (5.4% sequence divergence). None of these strains had a deoxyadenosine at base position 1251, when compared to the published sequence of strain GS clone pZVH14. Although this discrepancy did not affect the large tegument protein gene, it altered the predicted amino acid sequences of two putative proteins coded by open-reading frames 1 and 2 (ORF 1 and ORF 2) located upstream from this gene.

Blood buffy coat from Alzheimer's disease patients and their relatives does not transmit spongiform encephalopathy to hamsters

There was a report of spongiform encephalopathy transmitted to Syrian hamsters by intracerebral inoculation with the blood buffy coat of patients with Alzheimer's disease (AD) and their unaffected first-degree relatives. We attempted to verify that report, taking measures to reduce the risk of contaminating samples with agents causing spongiform encephalopathies. We obtained blood from 50 subjects, including six patients with familial AD, 21 unaffected first-degree relatives (siblings and offspring) of patients with familial AD, and 20 control subjects. We inoculated the buffy coats intracerebrally into Syrian LVG hamsters, observed them for signs of neurologic disease, examined their brains for neuropathologic changes at time of death, and performed serial (blind) passages by inoculating suspensions of all recovered brains into fresh LVG hamsters. We discerned no clinical illness or histopathologic changes resembling experimental spongiform encephalopathy in any hamster inoculated with human buffy coat nor in blind-passage hamsters, nor were the life spans of those hamsters shortened. We conclude that AD is not caused by an agent that transmits spongiform encephalopathy to hamsters.

Transmission of Creutzfeldt-Jakob disease to a chimpanzee by electrodes contaminated during neurosurgery

Stereotactic multicontact electrodes used to probe the cerebral cortex of a middle aged woman with progressive dementia were previously implicated in the accidental transmission of Creutzfeldt-Jakob disease (CJD) to two younger patients. The diagnoses of CJD have been confirmed for all three cases. More than two years after their last use in humans, after three cleanings and repeated sterilisation in ethanol and formaldehyde vapour, the electrodes were implanted in the cortex of a chimpanzee. Eighteen months later the animal became ill with CJD. This finding serves to re-emphasise the potential danger posed by reuse of instruments contaminated with the agents of spongiform encephalopathies, even after scrupulous attempts to clean them.

Human spongiform encephalopathy: the National Institutes of Health series of 300 cases of experimentally transmitted disease

We present a synthesis of clinical, neuropathological, and biological details of the National Institutes of Health series of 300 experimentally transmitted cases of spongiform encephalopathy from among more than 1,000 cases of various neurological disorders inoculated into nonhuman primates during the past 30 years. The series comprises 278 subjects with Creutzfeldt-Jakob disease, of whom 234 had sporadic, 36 familial, and 8 iatrogenic disease; 18 patients with kuru; and 4 patients with Gerstmann-Strüssler-Scheinker syndrome. Sporadic Creutzfeldt-Jakob disease, numerically by far the most important representative, showed an average age at onset of 60 years, with the frequent early appearance of cerebellar and visual/oculomotor signs, and a broad spectrum of clinical features during the subsequent course of illness, which was usually fatal in less than 6 months. Characteristic spongiform neuropathology was present in all but 2 subjects. Microscopically visible kuru-type amyloid plaques were found in 5% of patients with Creutzfeldt-Jakob disease, 75% of those with kuru, and 100% of those with Gerstmann-Sträussler-Scheinker syndrome; brain biopsy was diagnostic in 95% of cases later confirmed at autopsy, and proteinase-resistant amyloid protein was identified in Western blots of brain extracts from 88% of tested subjects. Experimental transmission rates were highest for iatrogenic Creutzfeldt-Jakob disease (100%), kuru (95%), and sporadic Creutzfeldt-Jakob disease (90%), and considerably lower for most familial forms of disease (68%). Incubation periods as well as the durations and character of illness showed great variability, even in animals receiving the same inoculum, mirroring the spectrum of clinical profiles seen in human disease. Infectivity reached average levels of nearly 10(5) median lethal doses/gm of brain tissue, but was only irregularly present (and at much lower levels) in tissues outside the brain, and, except for cerebrospinal fluid, was never detected in bodily secretions or excretions.

Belgrade virus, a cause of hemorrhagic fever with renal syndrome in the Balkans, is closely related to Dobrava virus of field mice

Belgrade virus is a recently described hantavirus that causes severe hemorrhagic fever with renal syndrome (HFRS) in people living in various parts of the Balkan Peninsula. Nucleotide sequencing of the G2-encoding region in the medium (M) segment of the viral genome, reverse transcribed and amplified by the polymerase chain reaction, revealed the Belgrade virus to be substantially different from Hantaan virus and other major serotypes of hantavirus but identical to Dobrava virus, a virus isolated from a field mouse (Apodemus flavicollis) in Slovenia. Belgrade virus may be an important cause of HFRS in the Balkan Peninsula, extending north toward the Alps. It poses a special danger to humans who have close contact with field rodents.

Long-term observations of human immunodeficiency virus-infected chimpanzees

Twenty-seven chimpanzees inoculated with material presumed to contain human immunodeficiency virus (HIV) between June 1983 and February 1985 were studied. The animals were examined on four to six occasions between 1989 and 1992 for serologic, virologic, hematologic, immunophenotypic, as well as clinical signs of HIV infection and compared to five uninfected control animals. The 19 animals that had seroconverted within 244 days of inoculation remained antibody positive, whereas those that did not seroconvert within 244 days of inoculation remained antibody negative 6 to 8 years later. HIV antigen was demonstrated at least once in lymphocyte cultures from 12 of the 19 antibody positive chimpanzees during this period. Nested polymerase chain reaction amplified proviral DNA in lymphocytes from 14 of the 19 animals. No proviral DNA was detected in antibody-negative animals. Antibody titers were generally higher in animals from which virus was recovered in lymphocyte cultures [granulocyte-macrophage (GM) titer, 1:8427] compared to virus-negative animals (GM titer, 1:3608). Mean total white blood cell and lymphocyte subtype counts were similar in the HIV-infected animals and uninfected controls. The high antibody levels and Western blot profiles, over periods as long as 9 years in these chimpanzees, suggest continuous stimulation of the immune system by HIV antigen although virus was detected only sporadically in the peripheral blood. No illness suggestive of immunodeficiency was seen.

[The use of a primary astrocyte culture for modelling HIV neurological infection]

The article deals with the results of the experiment substantiating the in vitro model of HIV neuro-infection. In this work primary glial (astrocytic) tissue cultures obtained from normal human and animal (guinea pig) brain tissue were used. As revealed in this investigation, the following phenomena could be observed in human brain tissue monolayer culture, infected with HIV and subsequently subcultured: (a) the stimulation of tissue-cell growth; (b) the formation of multinuclear glial cells; (c) the presence of virus-specific proteins in astrocyte cytoplasm, detected by immunofluorescent and electrophoretic techniques; (d) the presence of HIV-1 DNA provirus in infected astrocytes. Cyto-destruction was not observed, reverse transcriptase activity was absent.

Lack of JC viral genomic sequences in multiple sclerosis brain tissue by polymerase chain reaction

With DNA extracted from brain specimens from 19 multiple sclerosis, 5 progressive multifocal leukoencephalopathy, 1 Alzheimer's disease, and 8 nonneurological control subjects, polymerase chain reaction was performed using nested sets of primer pairs amplifying segments of the large T and VP1 antigen-encoding sequences of JC virus. Both sequences were detected in each of the 5 brain specimens of progressive multifocal leukoencephalopathy but in none of the 19 multiple sclerosis, 1 Alzheimer's disease, or the 8 control brain specimens.

Absence of measles, mumps, and rubella viral genomic sequences from multiple sclerosis brain tissue by polymerase chain reaction

We tested for measles, mumps, and rubella viruses in multiple sclerosis by polymerase chain reaction (PCR). Using RNA extracted from 19 multiple sclerosis and 8 control brain specimens, nested PCR was performed after reverse transcription (RT) of the RNA to cDNA using primer pairs directed against two regions in the genomes of measles and mumps viruses and one region in the rubella virus genome. Despite enhanced sensitivity of nested RT PCR, measles, mumps, and rubella viral genomic sequences were not found in any brain specimen.

Recommendations of the International Roundtable Workshop on Bovine Spongiform Encephalopathy

Recommendations of the working party were summarized as follows: Determine the status in all countries of their national cattle herds with respect to BSE. Attempt to develop a test to recognize BSE-infected animals before they become clinically ill. Establish procedures to prevent spread of BSE agent into the cattle populations, especially by eliminating feeds containing rendered ruminant proteins. Review the rendering processes, identify the sources and destinations of rendered products, and suggest appropriate changes if needed. Especially needed are standardized rendering procedures in regard to use of organic solvents, temperature, and duration of heat treatment. Review import and export regulations to reduce the risk of spreading BSE and to maximize opportunities for safe trading in cattle and cattle products. The scrapie-free certification program of the USDA was supported, and similar programs might be considered by other countries. If BSE/scrapie is diagnosed in a given country, determine baseline incidence of CJD in those countries and consider contributing to an international registry. The WHO should address the problems of BSE, formulate policy, participate in and coordinate research, and provide training opportunities for veterinary and human health care workers from eastern European countries and developing nations. Government and private agencies should consider increasing support for research on transmissibility and pathogenesis of CJD, BSE, CWD, scrapie, and transmissible mink encephalopathy. Prepare and publish a critical neuropathologic review of all spongiform encephalopathies, naturally and experimentally transmitted, defining the characteristics of each disease in the various species known to be susceptible. Consider producing guidelines for the biological and pharmaceutical industries with regard to sourcing, collecting, and processing bovine and ovine materials.(ABSTRACT TRUNCATED AT 250 WORDS)

Transmission of human T-cell leukemia virus type I from a patient with HTLV-I associated myelopathy/tropical spastic paraparesis and an asymptomatic carrier to rabbits

Rabbits were infected successfully with two strains of human T-cell leukemia virus type I (HTLV-I), one isolated from a Colombian patient with HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) and the other from an asymptomatic carrier. HTLV-I was repeatedly demonstrated in peripheral blood mononuclear cells (PBMNC) of infected rabbits, and the rabbits had elevated antibodies against the various structural proteins of HTLV-I. Four rabbits inoculated with HTLV-I-infected autologous lymphoid cells intravenously (i.v.) and intracerebrally (i.c.) had virus present in their PBMNC for more than 40 weeks, while those that were inoculated either with HTLV-I-infected human lymphoid cells or with autologous rabbit lymphoid cells intraperitoneally (i.p.) had episodes during which virus was not recovered from their PBMNC. The one rabbit inoculated i.p. developed antibodies to viral envelope glycoproteins earlier than did those inoculated i.v. and i.c. Rabbit lymphoid cell lines persistently infected with HTLV-I were established by cocultivating the rabbit PBMNC with HTLV-I-infected human lymphoid cells that had been irradiated or by inoculation with cell-free supernatant fluids of HTLV-I infected non-irradiated lymphoid cell cultures. HTLV-I-infected rabbit cell lines were of T-cell origin and expressed HTLV-I antigens by immunofluorescence. Electron microscopy revealed type-C retrovirus particles.

Detection of flaviviruses by reverse-transcriptase polymerase chain reaction

RNA sequences of five flaviviruses were detected by a modified polymerase chain reaction (PCR) that incorporated a reverse transcriptase and RNase inhibitor. Oligonucleotide primer pairs were synthesized to amplify sequences from St. Louis encephalitis (SLE), Japanese encephalitis (JBE), yellow fever (YF), dengue 2 (DEN-2), and dengue 4 (DEN-4) viruses. The amplified products were visualized as bands of appropriate size on ethidium bromide-stained agarose gels. The identity of these products was confirmed by restriction endonuclease cleavage to generate fragments of predicted lengths. The reverse-transcriptase PCR (RT-PCR) successfully amplified flavivirus sequences from cell cultures, frozen brain tissue, and formalin-fixed, paraffin-embedded brain tissue. The reactions were highly specific, and the method compared favorably to two conventional assays of viral infectivity. RT-PCR followed by PCR with nesting primers (N-PCR) was 1,000-fold more sensitive in detecting virus than classical infectivity titration by intracerebral inoculation of suckling mice and nearly 1,000-fold more sensitive than amplification of virus in cell culture followed by inoculation of mice.

Detection of hantavirus RNA in tissues of experimentally infected mice using reverse transcriptase-directed polymerase chain reaction

Detection of hantaviruses, the etiological agents of hemorrhagic fever with renal syndrome (HFRS), by virus isolation using experimental animals or cell culture is time-consuming. A more rapid but equally specific method is needed. We used a reverse transcriptase-directed polymerase chain reaction (RT-PCR) to detect hantavirus genomic sequences and compared its sensitivity with conventional virus isolation. RNA, extracted by the guanidinium isothiocyanate-cesium chloride method from hantavirus-infected Vero E6 cells and from tissues of infant mice inoculated intracerebrally with 100 LD50 of hantavirus, was initially reverse transcribed using avian myeloblastosis virus reverse transcriptase. The resulting complementary DNA (cDNA) was used as template to amplify the glycoprotein 2-encoding region of the hantavirus M segment. With this method, Vero E6 cell cultures infected with Hantaan virus strains 76-118 (prototype) and HV114 (an isolate from the urine of an HFRS patient in China) were positive, while control cultures were negative. Brain, lung, and heart tissues from hantavirus-infected mice were positive by RT-PCR at 5, 8, and 11 days after intracerebral inoculation. The specificity of the positive results was confirmed by restriction endonuclease digestion of the amplified fragments with AluI and HpaI. The sensitivity of the RT-PCR was equal to cell culture amplification but required less time. This method is being adapted for detection of hantavirus genomic sequences in clinical specimens and postmortem tissues from patients with HFRS.

Increased multimeric mitochondrial DNA in the brain of scrapie-infected hamsters

We observed a marked increase in multimeric mitochondrial DNA (mtDNA) in brains of scrapie-infected hamsters compared with those of uninfected hamsters. Homogenized brain tissue was subjected to subcellular fractionation to isolate scrapie-associated fibrils and tubulofilamentous structures. Nucleic acids were extracted from the scrapie-associated fibril/tubulofilament fraction which also contained mitochondria. Agarose gel electrophoresis revealed a band corresponding to the size of circular hamster mtDNA in both infected and uninfected samples, but slower migrating bands were observed only in samples from scrapie-infected brain. We showed by molecular cloning, nucleotide sequencing, and Southern blotting that the slower migrating bands are mtDNA. These findings confirm the recent demonstration by differential hybridization that multimeric mtDNA occurs in hamster scrapie brain. Elevated levels of multimeric circular mtDNA have been reported previously in various tumors and cultured cell lines.

Creutzfeldt-Jakob disease and kuru patients lack a mutation consistently found in the Gerstmann-Sträussler-Scheinker syndrome

We and others have recently reported that patients with the Gerstmann-Sträussler-Scheinker syndrome have a mutation at codon 102 of the gene coding for amyloid protein that accumulates in this disease. We report here that this mutation was not found in 5 familial and 27 sporadic cases of Creutzfeldt-Jakob disease or in 3 patients with kuru, so that although this mutation may be responsible for amyloidogenesis and transmissibility in Gerstmann-Sträussler-Scheinker syndrome, it cannot be the only cause of human spongiform encephalopathy.

Detection of measles virus genomic sequences in SSPE brain tissue by the polymerase chain reaction

The polymerase chain reaction (PCR) was modified to detect RNA genomic sequences by generating cDNA copies of these sequences as a preliminary step. Oligonucleotide primer pairs complementary to sequences in each of the five major structural protein genes of the measles virus (nucleocapsid protein, phosphoprotein, matrix protein, fusion protein, and hemagglutinin protein) were synthesized. PCR products were tentatively identified by visualization of bands of the appropriate size by ethidium bromide staining after gel electrophoresis, and identity was confirmed by subsequent restriction enzyme cleavage of the products at predetermined sites to yield fragments of predicted size. This method successfully amplified 400-500 base regions from each of these five genes in RNA extracts of wild measles virus cultured in Vero cells and in RNA extracted from most of the SSPE brain tissues tested, but not in RNA from any control brain tissues. Measles virus genome was detected in SSPE brain tissues stored frozen for as long as 27 years and formalin-fixed paraffin-embedded subacute sclerosing panencephalitis (SSPE) brain tissues as old as 9 years. This method provides a simple, rapid and highly sensitive means of detecting and identifying sequences of RNA genomes by PCR. The success of this method in detecting measles virus in SSPE brain tissue suggests that PCR is appropriate to investigate the possible presence of RNA viruses in other neurological disorders of unknown etiology.

Reevaluation of the ultrastructural pathology of experimental Creutzfeldt-Jakob disease. Serial studies of the Fujisaki strain of Creutzfeldt-Jakob disease virus in mice

We describe the serial ultrastructural pathology of experimental Creutzfeldt-Jakob disease (CJD) in mice. Spongiform vacuoles, widespread myelin and axonal pathology, accompanied by abundant macrophagic reaction and neuroaxonal dystrophy, were consistently found in mice infected with CJD virus. By contrast, intranuclear vacuolation and swelling of astrocytic and neuronal processes were nonspecific changes that also occurred in control animals. We conclude that CJD-related neuropathological phenomena do not accumulate gradually through the incubation period but develop relatively abruptly and in complete form.

High prevalence of human T-lymphotropic virus type I infection in isolated populations of the Western Pacific region confirmed by Western immunoblot

High prevalences of antibodies against human T-lymphotropic virus type I (HTLV-I), as confirmed by Western immunoblot, were found in several remote indigenous populations of the Solomon Islands and Vanuatu and in some isolated populations of New Guinea that had no contact with Japanese or Africans and little contact with Caucasians prior to our bleedings. By contrast, zero or very low prevalences of HTLV-I infection were found in Guamanians and Carolinians, despite more than 30 years of intense contact with the Japanese. A total of 1,601 sera, collected between 1963 and 1981 from 21 population groups in the Western Pacific, was tested by enzyme-linked immunosorbent assay (ELISA) for IgG antibodies to HTLV-I. By ELISA, prevalences of antibodies against HTLV-I ranged from zero to 50%. Seropositivity could be confirmed in only 12.5% of 48 ELISA-positive sera selected for testing by Western immunoblot. However, the confirmed HTLV-I seroprevalences in some Melanesian populations were still as high as those found in HTLV-I-endemic regions, such as southwestern Japan and the Caribbean basin. HTLV-I prevalences were similar among males and females, and acquisition of antibodies increased with age. Our data indicate that infections with HTLV-I or a related retrovirus have been widespread in the southwestern Pacific for over 25 year in populations with minimal outside contact, while some populations which had extensive Japanese contact have no evidence of infection. Furthermore, based on the high frequency of indeterminate Western immunoblots, we conclude that in Melanesia this may represent either incomplete specific reactivity to HTLV-I or the existence of an antigenic variant of HTLV-I, distinct from prototype Japanese, American, and European HTLV-I strains.

Mutations in familial Creutzfeldt-Jakob disease and Gerstmann-Sträussler-Scheinker's syndrome

A host protein encoded by the gene specifying the scrapie amyloid precursor affects pathogenesis of the transmissible spongiform encephalopathies: Creutzfeldt-Jakob disease (CJD), Gerstmann-Sträussler-Scheinker's syndrome (GSS), and kuru in man, and scrapie in animals. We found a mutation in this gene of two patients with CJD from one family and a second mutation in the same gene in three patients with GSS from another family. The mutation in two related familial CJD patients changed glutamine in position 200 tolysine. This mutation was absent in other individuals including unrelated patients with familial CJD, sporadic CJD, and GSS. The other mutation in three GSS patients changed proline in position 102 to leucine, the same mutation described recently in some GSS families. We did not find it in six unaffected relatives of the GSS patients or in other individuals including sporadic and familial CJD patients. A rare insertion described earlier in one CJD family was also absent in all tested individuals.

Serial ultrastructural studies of scrapie in hamsters

We report sequential studies of the ultrastructural neuropathology of the subcortical grey matter of hamsters infected with the 263K strain of scrapie virus. Vacuolation in this model develops relatively late in the incubation period, while tubulovesicular structures appear early. Furthermore, neuroaxonal dystrophy, accumulations of branching tubules, and neuronal change consisting of intracytoplasmic "whorls" of proliferating membranes constitute prominent features of scrapie-related neurodegeneration.

Scrapie-induced diabetes mellitus in hamsters

Scrapie-infected hamsters had slightly elevated non-fasting plasma glucose levels, markedly abnormal glucose tolerance tests, and impaired release of insulin in response to a glucose load. Plasma cortisol levels were essentially the same in infected and uninfected animals. Histological examination of the pancreas revealed no morphological changes in infected animals with no alteration in distribution of cells secreting insulin, glucagon and somatostatin. In contrast, brains of scrapie-infected animals had the diffuse vacuolation typical of spongiform encephalopathy. These experiments suggest that scrapie-induced diabetes mellitus in hamsters may result from damage to the central nervous system.

Antibodies to HTLV-I in populations of the southwestern Pacific

Sera collected from 1,102 individuals in 14 populations of the southwestern Pacific between 1956 and 1979 were tested by ELISA for antibodies to human T-cell leukemia virus type I (HTLV-I). Selected sera were also tested by particle agglutination and immunoblotting. Six of the populations had prevalences of antibodies greater than 4%, two populations had prevalences greater than 15%. Six populations had antibody prevalences of 2% or less. Three populations from the coast and northern islands of New Guinea had high prevalences of antibodies, while three New Guinea highland groups had virtually none. One population from the Solomon Islands had a high prevalence, while two others had very low prevalences. Two populations from small remote islands in Vanuatu both had high prevalences. Pacific sera did not neutralize a standard strain of virus readily neutralized by Japanese, European, and American sera. We conclude that infections with HTLV-I, some acquired more than 20 years ago, are widespread throughout the southwestern Pacific, even in several very isolated populations, although others have been spared. Some strains of HTLV-I in populations of the Pacific may have substantially different envelope proteins from prototype strains of America, Europe, and Japan.

Intracerebral inoculation of experimental animals with brain tissue from patients with schizophrenia. Failure to observe consistent or specific behavioral and neuropathological effects

To test the possibility that some cases of schizophrenia result from infection with a transmissible slow viral agent, 57 experimental animals (six chimpanzees, 12 Old World monkeys, 17 New World monkeys, and 22 guinea pigs) were inoculated intracerebrally with brain tissue from ten patients and followed up for six years. Behavioral comparisons with control animals revealed no consistent behavioral differences. Histological, immunohistochemical, and morphometric examination of brains of animals that died revealed no specific neuropathological abnormalities. These findings do not support a role for a virus-induced slow infection in the pathogenesis of schizophrenia but must be weighed against methodological limitations in animal susceptibility, disease communicability, and assay sensitivity.

Human immunodeficiency virus type 1 neutralization epitope with conserved architecture elicits early type-specific antibodies in experimentally infected chimpanzees

Chimpanzees are susceptible to infection by divergent strains of human immunodeficiency virus type 1 (HIV-1), none of which cause clinical or immunological abnormalities. Chimpanzees were inoculated with one of four strains of HIV-1: human T-lymphotropic virus (HTLV) type IIIB, lymphadenopathy virus (LAV) type 1, HTLV type IIIRF, or an isolate from the brain of a patient with acquired immunodeficiency syndrome. Within 6 months after inoculation with the closely related strains HTLV-IIIB or LAV-1, six chimpanzees developed serum antibodies to the C-terminal half (amino acids 288-467) of the HTLV-IIIB external envelope glycoprotein gp120. Sera from five of those chimpanzees had HTLV-IIIB cell-fusion-inhibiting antibody titers greater than or equal to 20 at that time, indicating that they neutralized the infecting strain of HIV-1 in vitro. No antibodies to the carboxyl terminus of HTLV-IIIB gp120 were observed in sera of chimpanzees inoculated with HTLV-IIIRF or with the brain-tissue strain, and those sera did not neutralize HTLV-IIIB. A rabbit immunized with the C-terminal portion of gp120 acquired neutralizing antibodies that bound to four domains of the HTLV-IIIB external envelope as analyzed by reactivity to 536 overlapping nonapeptides of gp120. One of these domains in the variable region V3, with the amino acid sequence IRIQRGPGRAFVTIG (amino acids 307-321), bound to all chimpanzee sera that neutralized HTLV-IIIB but not to the serum of the HTLV-IIIRF-inoculated chimpanzee that did not neutralize HTLV-IIIB. The HTLV-IIIRF sequence at the same location, ITKGPGRVIYA, was recognized by the serum of the HTLV-IIIRF-inoculated chimpanzee but not by any sera of the HTLV-IIIB-inoculated or LAV-1-inoculated chimpanzees. The HTLV-IIIB residues RIQR and AFV and the HTLV-IIIRF residues lysine and VIYA, flanking a highly conserved beta-turn (GPGR), appear to be critical for antibody binding and subsequent type-specific virus neutralization. This neutralization epitope, putatively consisting of a loop between two cysteine residues (amino acids 296 and 331) connected by a disulfide bond, is immunodominant in HIV-1-infected chimpanzees and induces antibodies restricted to the homologous viral strain.