Analysis of 27 mammalian and 9 avian PrPs reveals high conservation of flexible regions of the prion protein

Prion diseases are fatal neurodegenerative disorders in man and animal associated with conformational conversion of a cellular prion protein (PrPc) into the pathologic isoform (PrPSc). The function of PrPcand the tertiary structure of PrPScare unclear. Various data indicate which parts of PrP might control the species barrier in prion diseases and the binding of putative factors to PrP. To elucidate these features, we analyzed the evolutionary conservation of the prion protein. Here, we add the primary PrP structures of 20 ungulates, three rodents, three carnivores, one maritime mammal, and nine birds. Within mammals and birds we found a high level of amino acid sequence identity, whereas between birds and mammals the overall homology was low. Various structural elements were conserved between mammals and birds. Using the CONRAD space-scale alignment, which predicts conserved and variable blocks, we observed similar patterns in avian and mammalian PrPs, although 130 million years of separate evolution lie in between. Our data support the suggestion that the repeat elements might have expanded differently within the various classes of vertebrates. Of note is the N-terminal part of PrP (amino acid residues 23-90), which harbors insertions and deletions, whereas in the C-terminal portion (91-231) mainly point mutations are found. Strikingly, we found a high level of conservation of sequences that are not part of the structured segment 121-231 of PrPcand of the structural elements therein, e.g. the N-terminal region from amino acid residue 23-90 and the regions located upstream of alpha-helices 1 and 3.

A hypothalamic neuronal cell line persistently infected with scrapie prions exhibits apoptosis

Neuronal death and vacuolation are characteristics of the CNS degeneration found in prion diseases. Relatively few cultured cell lines have been identified that can be persistently infected with scrapie prions, and none of these cells show cytopathologic changes reminiscent of prion neuropathology. The differentiated neuronal cell line GT1, established from gonadotropin hormone releasing-hormone neurons immortalized by genetically targeted tumorigenesis in transgenic mice (P. L. Mellon, JJ. Windle, P. C. Goldsmith, C. A. Padula, J. L. Roberts, and R. I. Weiner, Neuron 5:1-10, 1990), was examined for its ability to support prion formation. We found that GT1 cells could be persistently infected with mouse RML prions and that conditioned medium from infected cells could transfer prions to uninfected cells. In many but not all experiments, a subpopulation of cells showed reduced viability, morphological signs of neurodegeneration and vacuolation, and features of apoptosis. Subclones of GT1 cells that were stably transfected with the trk4 gene encoding the high-affinity nerve growth factor (NGF) receptor (GT1-trk) could also be persistently infected. NGF increased the viability of the scrapie-infected GT1-trk cells and reduced the morphological and biochemical signs of vacuolation and apoptosis. GT1 cells represent a novel system for studying the molecular mechanisms underlying prion infectivity and subsequent neurodegenerative changes.

Prion protein gene variation among primates

Prion diseases are manifest as genetic, sporadic or infectious neurodegenerative disorders in humans and animals. The prolonged incubation times that accompany the transmission of prions between species are due, at least in part, to differences in prion protein (PrP) sequence. To examine the species barriers between non-human primates and humans, we sequenced the open reading frames (ORF) of 25 PrP genes from apes and monkeys. Comparison of the PrP genes of these animals with that of humans showed amino acid identities ranging from 92.9 to 99.6%. While phylograms of primate PrP sequences revealed a novel branching pattern for the apes, the genomic organization of all the primate PrP genes was similar, with the entire ORF contained within a single exon. Alignment of variant residues in primates, rodents and domestic animals showed no concordance with the mutations that segregate with human prion diseases or with polymorphisms that modulate disease in humans, mice and sheep. Most substitutions were conservative and, characteristically, clustered outside the four putative alpha-helical regions that are thought to form a four-helix bundle in the cellular isoform of PrP (PrPC). Deletion of one of five Gly-Pro rich octarepeats from the N-terminus of PrP was seen in some species, while squirrel monkeys had an additional octarepeat; squirrel monkeys have been frequently used as experimental hosts for transmission of human prions. Alignment of primate and other mammalian PrP sequences suggests that codons between 90 and 130 have a profound influence on the transmissibility of prions from one species to another.

The anticancer drug imatinib induces cellular autophagy

The tyrosine kinase inhibitor imatinib (Gleevec, Novartis Pharmaceuticals Corporation; Basel, Switzerland) is a powerful drug for treatment of chronic myelogenous leukemia (CML) and other malignancies. It selectively targets various tyrosine kinases, thereby leading to growth arrest of respective cancer cells. Given its wide application, it is of high importance to know all related underlying molecular mechanisms. We had previously found that imatinib increases the cellular clearance of intracellular protein aggregates by targeting the abl pathway and thereby upregulating lysosomal activity. Here, we describe that imatinib dose dependently activates the cellular autophagy machinery in mammalian cells, independently of tissue type, species origin or immortalization status of cells. Autophagy is an archetypical cellular degradation mechanism implicated in many physiological and pathophysiological conditions. Our data link for the first time the process of autophagy with the mode of action of imatinib. Induction of autophagy might represent an additional mechanism of imatinib to induce growth arrest, promote apoptosis in cancer cells and eventually even promote tumour regression.

PrPC directly interacts with proteins involved in signaling pathways

The cellular prion protein (PrP(C)) is a conserved glycoprotein predominantly expressed in neuronal cells. Its purpose in living cells is still enigmatic. To elucidate on its cellular function, we performed a yeast two-hybrid screen for interactors. We used murine PrP(C) (amino acids 23-231) as bait to search a mouse brain cDNA expression library. Several interaction partners were identified. Three of them with a high homology to known sequences were further characterized. These candidates were the neuronal phosphoprotein synapsin Ib, the adaptor protein Grb2, and the still uncharacterized prion interactor Pint1. The in vivo interaction of the three proteins with PrP(C) was confirmed by co-immunoprecipitation assays with recombinant and authentic proteins in mammalian cells. The binding regions were mapped using truncated PrP constructs. As both synapsin Ib and Grb2 are implicated in neuronal signaling processes, our findings further strengthen the putative role of the prion protein in signal transduction.

Individuals with antibodies against hepatitis B core antigen as the only serological marker for hepatitis B infection: high percentage of carriers of hepatitis B and C virus

BACKGROUND/AIMS

Several reports have unequivocally demonstrated that some individuals with antibodies against hepatitis B core antigen as the only serological marker for hepatitis B infection are chronic carriers of the hepatitis B virus. Nevertheless, conflicting data exist about the frequency of this phenomenon; its cause is unknown.

METHODS

In a prospective study we tested individuals who were positive for anti-HBc alone for HBV-DNA as well as for coexisting infections with human immunodeficiency virus and hepatitis C virus.

RESULTS

Using polymerase chain reaction with primer pairs from three different regions of the hepatitis B virus genome, we found 54 of 164 individuals (32.9%) with anti-HBc alone to be positive for hepatitis B virus, the majority of them showing very low hepatitis B virus concentrations. 14.3% were human immunodeficiency virus positive; half of them were also hepatitis B virus carriers. Surprisingly, 62 of 153 participants (40.5%) in this study showed antibodies against hepatitis C virus, and about two thirds of the latter were also positive for HCV-RNA. This finding could be confirmed by a retrospective analysis of all people tested for hepatitis B virus markers and anti-HCV in our institution during the 2 years before the prospective study was begun. Again, a high correlation was found between the presence of anti-HCV and anti-HBc alone: 49.2% of individuals with anti-HBc only were anti-HCV positive also, compared to 26.8% of HBsAg carriers and only 10% of individuals showing the serological pattern of past hepatitis B.

CONCLUSIONS

Thus our study of individuals positive for anti-HBc alone revealed a high number of carriers of hepatitis B virus and hepatitis C virus among them; furthermore, we found some evidence that hepatitis C virus infection may favour this unusual hepatitis B virus marker pattern.

Interspecies transmission of macaque simian T-cell leukemia/lymphoma virus type 1 in baboons resulted in an outbreak of malignant lymphoma

An outbreak of malignant lymphoma has been observed in one of the baboon (Papio hamadryas) stocks of Sukhumi Primate Center. More than 300 cases in this "high-lymphoma stock" have been registered since 1967. Human T-cell lymphotropic virus type 1 (HTLV-1)-related virus was implicated as the etiologic agent of Sukhumi baboon lymphoma. The origin of this virus remained unclear. Two possibilities were originally considered: the origin could be baboon simian T-cell leukemia/lymphoma virus type 1 (STLV-1) or HTLV-1 (before the outbreak started, some Sukhumi baboons were inoculated with human leukemic material). The third possibility entered recently: interspecies transmission of rhesus macaque STLV-1 to baboons. It was prompted by the finding of very close similarity between STLV-1 991-1cc (the strain isolated from a non-Sukhumi baboon inoculated with material from a Sukhumi lymphomatous baboon) and rhesus STLV-1. To test this hypothesis, we investigated 37 Sukhumi STLV-1 isolates from baboons of high-lymphoma stock by PCR discriminating rhesus type and baboon type STLV-1 isolates. All of them were proved to be rhesus type STLV-1. In contrast, all six STLV-1 isolates from baboons belonging to other stocks or populations were of baboon type. The PCR results were fully confirmed by DNA sequence data. The partial env gene gene sequences of all four STLV-1 isolates from Sukhumi lymphomatous baboons were 97 to 100% similar to the sequence of known rhesus STLV-1 and only 85% homologous with the sequence of conventional baboon STLV-1. Thus, interspecies transmission of STLV-1 from rhesus macaques (or closely related species) to baboons occurred at Sukhumi Primate Center. Most probably this event initiated the outbreak of lymphoma in Sukhumi baboons.

Analysis of non-infectious HIV particles produced in presence of HIV proteinase inhibitor

Newly developed substrate analogue peptidomimetics are able to inhibit the human immunodeficiency virus, HIV-1 proteinase at nanomolar concentration. In HIV infected cell culture they exhibit antiviral activity. We have analyzed the non-infectious HIV particles produced in chronically HIV infected cell culture in presence of one of these inhibitors. The total production of virus particles was not substantially reduced in drug treated cultures, compared to non-inhibited control cultures, but the infectivity of these virus particles was reduced about 100 fold. The processing of gag and gag-pol protein precursor was inhibited; only borderline activity of reverse transcriptase (RT) could be detected in these particles and they contained nonprocessed gag precursor protein. Thin section electron microscopy of inhibitor-treated, HIV-infected cells revealed reduced viral cytopathogenicity and both inhibition of particle assembly and incomplete maturation of the particles formed. The HIV particles produced in the presence of the proteinase inhibitor were studded with envelope glycoprotein knobs and often comprised multiple budding regions, but were morphologically immature.

Prominent stress response of Purkinje cells in Creutzfeldt-Jakob disease

To examine the role of stress-related 70-kDa heat shock proteins (Hsp-s) in Creutzfeldt-Jakob disease (CJD), we performed immunocytochemistry to detect Hsp-72 and Hsp-73, together with the abnormal (PrP(Sc)) and the presumed cellular form (PrP(C)) of the prion protein, and TUNEL method to measure cellular vulnerability in different brain regions in CJD and control cases. While Hsp-73 showed uniform distribution in all the examined samples, an increase in the number of Purkinje cells with prominent accumulation of Hsp-72 in the CJD group was observed. These neurons also showed intense PrP(C) staining, but TUNEL-positive nuclei were only detected in the granular (Hsp-72-negative) cell layer. Fewer cells of the inferior olivary nucleus were immunoreactive for Hsp-72 in CJD than in control cases, and regions showing severe spongiform change and gliosis exhibited fewer Hsp-72-immunoreactive neurons. Our results indicate that accumulation of the inducible Hsp-72 in certain cell types may be part of a cytoprotective mechanism, which includes preservation of proteins like PrP(C).

Detection by PCR of human polyomaviruses BK and JC in immunocompromised individuals and partial sequencing of control regions

Immunocompromised individuals were tested for the presence of the human polyomaviruses JC (JCV) and BK (BKV) by the polymerase chain reaction (PCR). The use of appropriate primers in a nested PCR allowed the detection of both viruses simultaneously. Viruses were differentiated by restriction fragment length analysis of amplified DNA fragments. Both BKV and JCV DNA were detected in the urine of an AIDS patient with progressive multifocal leukencephalopathy. In autopsy materials from this patient, JCV- but not BKV-DNA was found in brain and kidney tissue, whereas lung tissue was negative for both virus DNAs. To evaluate the methodology further, hybridization-positive urines from three recipients of bone marrow transplants and a positive urine of an acute myeloid leukemia patient were analyzed by this PCR method. One case was positive both for BKV and JCV, two cases were positive only for BKV, and one was negative for both. Parts of the control regions of JCV and BKV were sequenced directly from PCR-derived fragments. The JCV sequence from urine of the AIDS patient compared to sequences from a bone marrow transplant recipient and to archetypical reference strains showed two nucleotide (nt) exchanges out of 250 nt. The BKV sequences from the AML and the AIDS patients showed five nt exchanges out of 265 nt in the control region and were identified as BKV WW or WWT3 strains. In the agnogene region five exchanges were detected, two of them resulting in non-conservative amino acid exchanges. The possibility of testing clinical specimens of different origins by this PCR method is important for elucidating often unclear clinical courses in immunocompromised patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Vaccination against hepatitis A: comparison of different short-term immunization schedules

A total of 114 healthy young adults were immunized with hepatitis A vaccine using different vaccination schedules. Individuals received either a single dose (group 1), two doses given simultaneously (group 2), two doses at days 0 and 14 (group 3) or at days 0 and 28 (group 4), or three doses at days 0, 7 and 21 (group 5). Two weeks after a single dose, seroconversion rates between 77 and 85% were achieved (groups 1, 3, 4). All individuals immunized with two doses within two weeks (groups 2, 3, 5) had antibodies to hepatitis A vaccine (anti-HAV positive) by week 3; these participants also showed clearly higher mean anti-HAV values (geometric mean titres, GMTs) at this time than those individuals vaccinated only once. GMTs at week 8 were 560 IU/l in group 5, 236, 339 and 428 IU/l in groups 2-4 and 102 IU/l in group 1. Of participants with anti-HAV at week 8, 82 were again tested 4 months later; all were still seropositive. Ten individuals were tested during the first three weeks at 3-4 day intervals for anti-HAV immunoglobulin M (IgM); specific IgM responses were not detectable before day 10 but were present in eight of 10 vaccinees by day 14.

A recombinant Toscana virus nucleoprotein in a diagnostic immunoblot test system

Sandfly fever, a vector-borne disease endemic in the Mediterranean region, is caused by Toscana virus (TOS). The disease is increasingly important as a travel-related infection. Serological diagnosis is currently dependent on viral antigens derived from TOS-infected cell cultures. In this study, we report the cloning and expression of the TOS nucleoprotein (N) in Escherichia coli and evaluation of the recombinant (r) TOS N protein as an antigen for immunoblot assays. The TOS N gene was amplified by reverse-transcriptase polymerase chain reaction and cloned into the bacterial expression vector pTrcHis-A. Sera with known TOS antibody status were used to evaluate the immunoblot assay. The expressed rTOS N protein was purified and used as antigen for immunoblots. By recombinant immunoblot, the TOS antibody status (IgM and/or IgG) of the test panel was correctly identified. No cross-reactivity was detected. The rTOS N protein is useful as an antigen for immunoblot assays, and will enable more laboratories to perform TOS antibody diagnosis.

A seroepidemiological survey of antibodies to HTLV-I/HTLV-II in selected population groups in Paraguay

Between March 1987 and November 1989 a cross-sectional serological survey was conducted on 884 residents of Paraguay to obtain data on the prevalence of antibodies to human T-cell leukemia virus type I/II (HTLV-I/II). Sera from 8/884 individuals (0.9%) were positive, confirmed by Western blotting and radioimmunoprecipitation (RIPA). This study shows that HTLV-I/II is very rare (or absent) among the general (healthy) population (0/338) and ethnic Japanese (0/227) in Paraguay. However, it can be detected at a rate of 2-3% in prostitutes (4/178) and homosexuals (4/117), suggesting sexual transmission as an important route for spread of HTLV-I/II in Paraguay.

Prevalence of human T-cell lymphotropic virus infections in Germany

The extent of human T-cell lymphotropic retrovirus HTLV-I and HTLV-II infections in the general population in central Europe has not been investigated fully. Two hundred forty-eight thousand blood donors from southern Germany were examined serologically for antibodies to the human lymphotropic retroviruses HTLV-I and HTLV-II: 0.021% were confirmed positive and 0.056% were "indeterminate". A limited number of seropositives and "indeterminate" samples were analyzed by polymerase chain reaction (PCR): the seropositives were confirmed as positive and 43% of the "indeterminate" samples were PCR-positive. The range of 0.021% HTLV-positives in 248,000 donors, i.e. about two in 10,000 individuals, mirrors closely the published data for the United States.

Shortest known prion protein allele in highly BSE-susceptible lemurs

We describe the shortest prion protein allele known to date. Surprisingly, it is found as a polymorphism exactly in a species (prosimian lemurs) which seems highly susceptible to oral infection with BSE-derived prions. The truncation of the prion protein we found raises several questions. First, is the truncated octarepeat structure we describe, consisting of two octarepeats, still functional in copper binding? A second question is whether this truncation is related to the remarkable oral infectibility of lemurs with BSE-derived prions. And finally, one could argue that this genotype alone might favour development of a prion disease, even in the absence of exogenous infection.

[Reuse of "single use" medical devices after quality assured reprocessing: hygienic, legal and economic aspects. Potential for cost savings in interventional cardiology]

The increasing limitation of resources has stimulated the discussion of the reuse of medical devices labelled for "single use" by the manufacturer. The prerequisites for employment of reprocessing measures are patient safety and cost saving potential. Although reprocessing of single use medical devices has been general practice by many institutions, health care providers and authorities have remained insecure as to hygienic and functional risks, liability and legal aspects. Changes in legislation (German Medical Device Act), guidelines of the Robert Koch Institute (and position of the FDA) and the high quality guaranteed by innovative reprocessing technology have now created the basis for expanded but controlled use of reprocessing techniques for medical devices as a contribution to cost containment. A significant cost saving potential is calculated for the cost-intensive field of interventional cardiology.

The immune response to different doses of inactivated hepatitis A vaccine

The immunogenicity and reactogenicity of different doses of hepatitis A vaccine was studied in healthy adult volunteers. Vaccinees (105) were immunized with 6.25, 12.5 or 25 ng of HAV antigen, each dose administered at 0, 1 and 6 months (groups B, C and D); one group (group A) obtained three 6.25 ng doses at 0, 1 and 2 months. After one single dose high seroconversion rates ranging between 63 and 85% were observed in all four groups. All participants had seroconverted after the third dose, irrespective of the antigen content per dose and the vaccination schedule. Geometric mean titers after three doses were 439 IU/l (group A, month 3) and 1492, 963 and 2772 IU/l in groups B, C and D at month 7. One year after the first injection all vaccinees tested still showed antibody levels well above 10 IU/l. The vaccine was very well tolerated. Minor localized symptoms were observed mainly such as slight pain at the injection site. These symptoms were not dose related; no serious side effects occurred.

The Sukhumi primate monkey model for viral lymphomogenesis: high incidence of lymphomas with presence of STLV-I and EBV-like virus

T-cell leukemia virus-like proviral sequences (STLV-I) as well as EBV-like sequences were detected in PBLs and tissues of non-human primates (Papio hamadryas baboons, Green monkeys and Macaca arctoides; Sukhumi Primate Center/Georgia) by PCR. Surprisingly, two different types of STLV-I within Papio hamadryas baboons were found. One of its represents the baboon prototype STLV-I-Su described earlier, present in lymphomatous baboons from the "high-lymphoma stock", which shows about 83% homology to HTLV-I and 85% to STLV-I in the env and tax genes. The inter-individual variability within this subtype is very low (about 1% in the tax gene). The second subtype was mainly found in asymptomatic animals from the control colony and showed in the env gene 95% homology to HTLV-I, but only 82% to the prototype baboon sequence. The presence of two subtypes within the Sukhumi baboon population might be interesting in respect to the inoculation experiments with human leukemic blood and to possible interspecies transmissions. The nature of the Herpes Papio-virus was elucidated as EBV-like and the homology to the human EBV was > 90% in the polymerase gene. The homologies between different monkey species were between 92 and 96% and also here two subtypes within the baboons were detected. This is the first direct demonstration by sequencing that the Herpes Papio virus is closely related to EBV. For further studies of this animal model, rabbits were inoculated with cells originated from lymphomatous baboons and macaques. The rabbits developed generalized lymphomas lethal within 1-2 months. EBV-like and STLV-I-like sequences could be detected by PCR and sequencing showed 99-100% identity to the inoculum, indicating in fact the transmission from monkey to rabbit. These animal models seem to be very suitable for the elucidation of the pathogenesis of human HTLV-I associated T-cell leukemia/lymphoma and might be further on used for therapeutical and preventative studies.

V-sis gene (SSV) is expressed transiently and independently of v-gag (SSAV) after infection of fibroblasts with SSV/SSAV

To investigate the mechanism of cell transformation by the retroviral v-sis gene, we examined the mode of its mRNA expression after infection of primate fibroblasts with Simian Sarcoma Virus (SSV/SSAV). Surprisingly transient expression of the 5.3 kb transcript of v-sis was detected between day two and four after infection. Addition of cycloheximide did not reverse the down-regulation of v-sis expression. Suramin, which uncouples the PDGF receptor complex, had no effect on the pattern of v-sis expression. A marginal but non-transient expression of c-myc and c-fos mRNA upon v-sis expression was detected. Studies on nuclear run-off and m-RNA stability suggest that the half-life time of v-sis mRNA is about 8 h or longer and that its expression is controlled rather by transcriptional than by post-transcriptional mechanisms. The up and down regulation of v-sis expression is independent of the expression of the helper virus (SSAV) gag-genes. This indicates that v-sis oncogene (SSV) and structural genes of the helper virus (SSAV) are obviously under separate expression control.

Quantification of hepatitis B virus DNA over a wide range from serum for studying viral replicative activity in response to treatment and in recurrent infection

A new standardized test for hepatitis B virus (HBV) DNA with increased sensitivity and range over previous assays (30 to 10(6) HBV genomes/test) was evaluated in this study. The quantitative results from the test have been validated using international reference specimens of known titer and a reference solution hybridization test. The test has small variability considering the wide dynamic range. The CV was 14% within one experiment and 32% to 39% between independent experiments. Hepatitis B surface antigen (HBsAg)-negative, anti-HBc-positive blood donor sera (n = 25) were all negative for HBV DNA in the new test, whereas 63% (n = 19) of HBsAg-positive healthy carriers had measurable quantities of HBV DNA. In five example cases of chronic hepatitis B patients responding to alfa-interferon treatment but remaining virus positive, HBV DNA was consistently present in posttreatment sera in a titer range 4 x 10(3) to 10(6)/mL not detectable by the conventional hybridization test. In two complete responders, the HBV DNA titer decreased over six orders of magnitude to below cutoff of the test. In four liver transplant recipients with chronic hepatitis B, viral recurrence was detected by the new test at an early stage much before the clinical relapse. Unlike serology, the test was suitable also in patients under anti-HBs immunoprophylaxis. In conclusion, the new colorimetric polymerase chain reaction (PCR) test allowed thousandfold increased sensitivity in quantification of HBV DNA in patient sera. The test may have future applications in improving assessment of efficacy of antiviral treatment and guiding therapeutic interventions.