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Original Article

A Test for Creutzfeldt–Jakob Disease Using Nasal Brushings

List of authors.
  • Christina D. Orrú, Ph.D.,
  • Matilde Bongianni, Ph.D.,
  • Giovanni Tonoli, M.D.,
  • Sergio Ferrari, M.D.,
  • Andrew G. Hughson, M.S.,
  • Bradley R. Groveman, Ph.D.,
  • Michele Fiorini, Ph.D.,
  • Maurizio Pocchiari, M.D.,
  • Salvatore Monaco, M.D.,
  • Byron Caughey, Ph.D.,
  • and Gianluigi Zanusso, M.D., Ph.D.

Abstract

Background

Definite diagnosis of sporadic Creutzfeldt–Jakob disease in living patients remains a challenge. A test that detects the specific marker for Creutzfeldt–Jakob disease, the prion protein (PrPCJD), by means of real-time quaking-induced conversion (RT-QuIC) testing of cerebrospinal fluid has a sensitivity of 80 to 90% for the diagnosis of sporadic Creutzfeldt–Jakob disease. We have assessed the accuracy of RT-QuIC analysis of nasal brushings from olfactory epithelium in diagnosing sporadic Creutzfeldt–Jakob disease in living patients.

Methods

We collected olfactory epithelium brushings and cerebrospinal fluid samples from patients with and patients without sporadic Creutzfeldt–Jakob disease and tested them using RT-QuIC, an ultrasensitive, multiwell plate–based fluorescence assay involving PrPCJD-seeded polymerization of recombinant PrP into amyloid fibrils.

Results

The RT-QuIC assays seeded with nasal brushings were positive in 30 of 31 patients with Creutzfeldt–Jakob disease (15 of 15 with definite sporadic Creutzfeldt–Jakob disease, 13 of 14 with probable sporadic Creutzfeldt–Jakob disease, and 2 of 2 with inherited Creutzfeldt–Jakob disease) but were negative in 43 of 43 patients without Creutzfeldt–Jakob disease, indicating a sensitivity of 97% (95% confidence interval [CI], 82 to 100) and specificity of 100% (95% CI, 90 to 100) for the detection of Creutzfeldt–Jakob disease. By comparison, testing of cerebrospinal fluid samples from the same group of patients had a sensitivity of 77% (95% CI, 57 to 89) and a specificity of 100% (95% CI, 90 to 100). Nasal brushings elicited stronger and faster RT-QuIC responses than cerebrospinal fluid (P<0.001 for the between-group comparison of strength of response). Individual brushings contained approximately 105 to 107 prion seeds, at concentrations several logs10 greater than in cerebrospinal fluid.

Conclusions

In this preliminary study, RT-QuIC testing of olfactory epithelium samples obtained from nasal brushings was accurate in diagnosing Creutzfeldt–Jakob disease and indicated substantial prion seeding activity lining the nasal vault. (Funded by the Intramural Research Program of the National Institute of Allergy and Infectious Diseases and others.)

Introduction

Prion diseases, or transmissible spongiform encephalopathies, are fatal neurodegenerative disorders in humans and animals.1,2 Prion diseases include Creutzfeldt–Jakob disease, the Gerstmann–Sträussler–Scheinker syndrome, and fatal familial insomnia in humans. The most common form of human prion disease is sporadic Creutzfeldt–Jakob disease, with an incidence of approximately 1 case per million persons per year worldwide.3 Sporadic Creutzfeldt–Jakob disease is clinically heterogeneous and includes forms characterized by psychotic symptoms, depression, and behavioral and personality changes.4,5 Possible or probable sporadic Creutzfeldt–Jakob disease is defined on the basis of clinical features, as well as periodic sharp and slow wave complexes on electroencephalograms, a positive 14-3-3 protein assay of cerebrospinal fluid samples, and altered signals on brain magnetic resonance images (MRI).6 Definite diagnosis of sporadic Creutzfeldt–Jakob disease requires neuropathological or immunochemical detection of the prion protein (PrPCJD) in brain tissue.7 The heterogeneity of sporadic Creutzfeldt–Jakob disease phenotypes is influenced by the methionine (M)–valine (V) polymorphism at codon 129 of the prion protein gene (PRNP)8 and the glycoform type (1 or 2) of PrPCJD. PrPCJD arises through the post-translational conformational conversion of the normal endogenous PrP (PrPC or PrPSen) and accumulates preferentially in nervous tissue. PrPCJD is also the main component of the infectious Creutzfeldt–Jakob disease agent (prion)1,2,9-13 and propagates itself by seeding or templating the assembly of PrPC into misfolded multimers that can take the form of amyloid fibrils.2,10,11,13-15

Although PrPCJD is the only specific marker for Creutzfeldt–Jakob disease, it has been difficult to identify a PrPCJD assay and a procedure for obtaining a tissue specimen that together are sufficiently sensitive, noninvasive, and practical for use in living patients. Recently, testing of cerebrospinal fluid with a new in vitro PrPCJD amplification technology, designated real-time quaking-induced conversion (RT-QuIC), has shown considerable promise as a highly specific diagnostic test for sporadic Creutzfeldt–Jakob disease.16,17 In the RT-QuIC assay, recombinant prion protein (rPrPSen) is mixed, or seeded, with a small amount of PrPCJD, resulting in the formation of amyloid fibrils that are detected by thioflavin T (ThT) fluorescence.17,18 This quantitative assay detects seeding activity in brain homogenate from humans with sporadic Creutzfeldt–Jakob disease that is diluted by a factor of more than 108.18,19 Such diluted samples contain femtogram levels of protease-resistant PrPCJD. Applications of RT-QuIC to panels of cerebrospinal fluid samples from patients with and patients without sporadic Creutzfeldt–Jakob disease have shown sensitivities for the detection of sporadic Creutzfeldt–Jakob disease (percent positive of the total number of patients with the disease) of 80 to 90% and specificities (percent negative of total number of controls without the disease) of 99 to 100%.16,17 These studies suggest that RT-QuIC can achieve greater diagnostic performance than tests for surrogate markers of sporadic Creutzfeldt–Jakob disease in the cerebrospinal fluid.

Because RT-QuIC analysis of cerebrospinal fluid failed to identify 10 to 20% of patients with sporadic Creutzfeldt–Jakob disease, we sought to improve the sensitivity and practicality of diagnostic testing by applying the RT-QuIC technology to olfactory epithelium samples. PrPCJD accumulates in the olfactory epithelium of patients with sporadic Creutzfeldt–Jakob disease, which suggests that analyses of olfactory mucosa–biopsy specimens might be diagnostic for patients with sporadic Creutzfeldt–Jakob disease.20,21 However, only small, discrete units of tissue are obtained in olfactory mucosa biopsies, and, given the fact that the olfactory epithelium in the nasal vault is interspersed with PrPCJD-negative respiratory mucosa,20 analyses of olfactory mucosa for markers of Creutzfeldt–Jakob disease might provide false negative results if the biopsy misses the olfactory epithelium. In addition, surgical complications such as bleeding, infections, or traumatic injury can occur. Here we describe a much safer and less invasive nasal-brushing procedure that allows a gentle collection of olfactory mucosa from a wide surface area of olfactory epithelium. In this study, we assessed how well RT-QuIC analysis of olfactory mucosa brushings could discriminate patients with sporadic Creutzfeldt–Jakob disease from controls who did not have the disease.

Methods

Patients with Creutzfeldt–Jakob Disease and Controls

Table 1. Table 1. Demographic Characteristics, Clinical Profiles, Diagnostic Factors, and Real-Time Quaking-Induced Conversion (RT-QuIC) Analyses of Patients with Creutzfeldt–Jakob Disease. Table 2. Table 2. Results of RT-QuIC Assays of Olfactory Mucosa and Cerebrospinal Fluid Samples.

We used a variety of tests (Table 1) to classify 31 patients with rapidly progressive dementia who were referred to our institutions by their treating physicians from various regions of Italy because of possible or probable Creutzfeldt–Jakob disease. Two of the patients were subsequently found to have inherited Creutzfeldt–Jakob disease resulting from E200K PRNP mutations. At the time of referral and during follow-up, all the patients were classified according to updated clinical diagnostic criteria.5 Olfactory mucosa controls included 12 patients with other neurodegenerative disorders such as Alzheimer’s disease or Parkinson’s disease (8 women and 4 men; mean [±SD] age, 70.8±8.8 years; range, 48 to 82) and 31 persons without neurologic disorders (11 women and 20 men; mean age, 52.1±15.0 years; range, 24 to 81), who were, in most cases, referred to the ear, nose, and throat clinic for other purposes (Table 2).

Study Oversight

The study was approved by the ethics committee at Istituto Superiore di Sanità (Italy), which is recognized by the Office for Human Research Protections of the U.S. Department of Health and Human Services. Informed consent for participation in research was obtained in accordance with the Declaration of Helsinki and the Additional Protocol to the Convention on Human Rights and Biomedicine, concerning Biomedical Research. All the sampling of olfactory mucosa was performed after written informed consent was obtained from each patient or the patient’s representative. The analyses of human specimens that were performed at the National Institute of Allergy and Infectious Diseases were performed under Exemption 11517 for the use of encoded samples from the National Institutes of Health Office of Human Subjects Research Protections.

Brain Tissue

Brain-tissue specimens were obtained at autopsy from 15 patients with sporadic Creutzfeldt–Jakob disease and were processed for neuropathological examination and biochemical analyses. Control brain samples were provided by the National Institute for Biological Standards and Control, United Kingdom. Brain homogenate samples, 10% (weight:volume), were prepared22 and serially diluted in 0.1% sodium dodecyl sulfate (SDS) in phosphate-buffered saline (PBS) containing 1× N2 medium supplement (GIBCO) (SDS–PBS–N2) before RT-QuIC analysis.

Olfactory Mucosa and Cerebrospinal Fluid Samples

Olfactory mucosa or cerebrospinal fluid samples (>0.5 ml) were obtained from the patients with possible or probable Creutzfeldt–Jakob disease at the time of sampling, as well as from the patients with other neurologic disorders, including probable Alzheimer’s disease23 (5 olfactory mucosa and 13 cerebrospinal fluid samples), probable Parkinson’s disease24 (4 olfactory mucosa and 4 cerebrospinal fluid samples), probable progressive supranuclear palsy (1 olfactory mucosa and 1 cerebrospinal fluid sample), definite progressive supranuclear palsy25 (1 olfactory mucosa and 1 cerebrospinal fluid sample), and paraneoplastic limbic encephalitis (1 olfactory mucosa and 1 cerebrospinal fluid sample) (Table 2). In five of these patients with other neurologic disorders, both olfactory mucosa and cerebrospinal fluid samples were obtained. Additional olfactory mucosa control samples were obtained from the 31 persons without neurologic disorders who had been admitted to the ear, nose, and throat clinic for other purposes. Cerebrospinal fluid control samples were purchased from Innovative Research or obtained from the Neuropathology Laboratory at Verona University Hospital. Two separate cerebrospinal fluid samples were obtained from 4 of the patients with Creutzfeldt–Jakob disease. All cerebrospinal fluid and olfactory mucosa samples were stored at −80°C from a time shortly after harvest until use in this assay.

Preparation of Olfactory Mucosa Samples

Patients were not sedated when the olfactory mucosa samples were obtained. After administration of a local vasoconstrictor (1% epinephrine) with the use of a nasal tampon, a rigid fiberoptic rhinoscope, enveloped with a disposable sheath (Slide-On EndoSheath System, Medtronic Xomed) to prevent contamination, was inserted into the nasal cavity of the patient to locate the olfactory mucosa lining the nasal vault (Fig. S1A in the Supplementary Appendix, available with the full text of this article at NEJM.org). A sterile, disposable brush (Kito-Brush, Kaltek or Hobbs Medical) was then inserted alongside the fibroscope, gently rolled on the mucosal surface, withdrawn, and immersed in saline solution in a 15-ml conical centrifuge tube. Cellular material was dissociated from the brush by means of vortexing. The brush was withdrawn, and particulate matter was pelleted for 20 minutes at 2000×g at 4°C and frozen at −80°C. The olfactory mucosa pellet samples were thawed and centrifuged for 10 minutes at 3220×g at 4°C. The residual supernatant was removed, and a disposable inoculating loop (Fisherbrand) was dipped into the pellet to transfer approximately 1 to 2 μl of the pellet into a tube containing 25 μl PBS. The latter tube was sonicated until the pellet was dispersed and further diluted, as specified, in SDS–PBS–N2.

RT-QuIC Analysis

For spiking experiments, 2 μl of brain homogenate dilutions in SDS–PBS–N2 were added to 48 μl of olfactory mucosa pellet after the latter had been diluted, as described above, in SDS–PBS–N2. RT-QuIC reactions were performed as described previously18 with 2 μl of the spiked olfactory mucosa dilution as a seed and full-length hamster PrP residues 23 to 231 as the rPrPSen substrate. The total reaction volume was 100 μl. For analysis of endogenous seeding activities, 2 μl of diluted olfactory mucosa or brain homogenate or 20 μl of undiluted cerebrospinal fluid was used to seed the reactions. RT-QuIC reactions were subjected to cycles of shaking and rest at 42°C for 55 to 90 hours as described previously.18 The criteria for discriminating positive versus negative RT-QuIC tests of cerebrospinal fluid and olfactory mucosa samples are explained in the Methods section in the Supplementary Appendix.

Statistical Analysis

Statistical comparisons of mean relative ThT fluorescence responses in samples from patients with and patients without Creutzfeldt–Jakob disease were performed with unpaired t-tests. Calculations of 95% confidence intervals for sensitivities and specificities were performed with the use of the Wilson procedure.26

Results

RT-QuIC Analysis of Olfactory Mucosa Samples Spiked with Brain Tissue

Brushings of the nasal vault (Fig. S1A in the Supplementary Appendix) yielded samples containing clusters of olfactory neurons (Fig. S1B and S1C in the Supplementary Appendix) in addition to respiratory ciliated cells and a few granulocytes and monocytes (data not shown). Spiking of an olfactory mucosa sample from a patient without Creutzfeldt–Jakob disease with brain homogenate from a patient with sporadic Creutzfeldt–Jakob disease that was diluted by a factor of 4×10−7 and 4×10−8 (containing approximately 20 femtograms and approximately 2 femtograms of protease-resistant PrPCJD, respectively) induced strong ThT fluorescence, with the more concentrated brain homogenate giving more rapid amplification kinetics (Fig. S2 in the Supplementary Appendix). The increased fluorescence indicated formation of amyloid fibrils by the initially monomeric rPrPSen. In the case of both of the brain homogenate dilutions, similar kinetics were also observed when the brain homogenates were diluted into the same buffer without any olfactory mucosa, indicating that olfactory mucosa components (diluted 1:250 overall) did not inhibit RT-QuIC.

Endogenous Olfactory Mucosa Seeding Activity

RT-QuIC dilution analysis of an olfactory mucosa brushing sample from a patient with sporadic Creutzfeldt–Jakob disease showed that all four replicate reactions that were seeded with 1:250 and 1:2500 dilutions of the olfactory mucosa pellet gave strong ThT positivity within 30 hours (Fig. S3 in the Supplementary Appendix). The 1:25,000 dilution was ThT-positive in two of four replicate wells within approximately 50 hours. In contrast, none of the same dilutions of an olfactory mucosa sample from patients without Creutzfeldt–Jakob disease gave positive reactions within 60 hours. These data indicated that the olfactory mucosa pellets from the patient with sporadic Creutzfeldt–Jakob disease had several logs10 of RT-QuIC seeding activity (see also below).

We then tested blinded sets of samples comprising 74 olfactory mucosa samples from patients with definite sporadic Creutzfeldt–Jakob disease (15 samples), probable sporadic Creutzfeldt–Jakob disease (14), or inherited (E200K PRNP mutation) Creutzfeldt–Jakob disease (2) and from negative controls without Creutzfeldt–Jakob disease (43). Table 1 summarizes the demographic and clinical features of the patients with sporadic Creutzfeldt–Jakob disease, as well as the results of MRI, electroencephalography, and cerebrospinal fluid analyses. The patients with sporadic Creutzfeldt–Jakob disease had MM, MV, or VV at residue 129 of the PrP sequence and either the type 1 or type 2 PrPCJD, according to subsequent assessment of brain tissue.8

Figure 1. Figure 1. Results of Real-Time Quaking-Induced Conversion (RT-QuIC) Assays of Olfactory Mucosa (OM) and Cerebrospinal Fluid (CSF) Samples.

Panel A shows the average percent thioflavin T (ThT) fluorescence readings from four replicate reactions (normalized as described in the Methods section), determined in samples of OM and CSF from patients with possible, probable, or definite Creutzfeldt–Jakob disease and from controls without Creutzfeldt–Jakob disease. The means (thick lines) with standard deviations (thin lines) of those averages are shown as a function of RT-QuIC reaction time. Panel B shows the final average relative ThT fluorescence readings for each person with Creutzfeldt–Jakob disease (CJD) and for each control with either a neurologic disease other than Creutzfeldt–Jakob disease (other neurologic disease [OND]) or no neurologic disease (NND) at either 50 hours (OM samples) or 90 hours (CSF samples). Inherited CJD refers to patients with the E200K PRNP genetic mutation causing CJD. All OM and CSF samples obtained from patients with CJD and from controls are reflected in these data. The total number of CSF samples from patients with CJD (34) does not include a sample from one patient (Patient 31; CSF not tested) and includes results from two lumbar punctures each in four patients with CJD.

As evaluated according to the criteria described in the Methods section in the Supplementary Appendix, positive RT-QuIC reactions were observed in 1:250 dilutions of olfactory mucosa samples from 15 of 15 patients with definite sporadic Creutzfeldt–Jakob disease, 13 of 14 with probable sporadic Creutzfeldt–Jakob disease, and 2 of 2 with inherited (E200K) Creutzfeldt–Jakob disease (Table 2). Individual RT-QuIC traces from the first 14 patients with sporadic Creutzfeldt–Jakob disease are shown in Figures S4A through S4N in the Supplementary Appendix, and traces averaged from all the sporadic and inherited (E200K) cases of Creutzfeldt–Jakob disease are shown in Figure 1A. In contrast, olfactory mucosa samples from all 43 control patients without Creutzfeldt–Jakob disease were RT-QuIC–negative at the same dilution (Figure 1A and 1B and Table 2, and Fig. S4O and S4P in the Supplementary Appendix). The final average normalized ThT fluorescence readings at 50 hours from four replicate reactions in specimens from all the patients with sporadic Creutzfeldt–Jakob disease and the controls without Creutzfeldt–Jakob disease are shown in Figure 1B. The single patient with apparent Creutzfeldt–Jakob disease (Patient 29) for whom neither olfactory mucosa nor cerebrospinal fluid samples showed a positive RT-QuIC reaction (Figure 1B and Table 1) received a diagnosis of probable Creutzfeldt–Jakob disease on the basis of established criteria and had tau and 14-3-3 protein levels that were typical of sporadic Creutzfeldt–Jakob disease. Overall, we obtained 30 positive RT-QuIC tests from 31 patients with apparent Creutzfeldt–Jakob disease, representing an estimated sensitivity of 97% (95% confidence interval [CI], 82 to 100) for distinguishing patients with Creutzfeldt–Jakob disease from those without the disease. If we considered only the definite cases of sporadic Creutzfeldt–Jakob disease, the estimated sensitivity would be 100% (95% CI, 75 to 100). The negative tests from all 43 control patients without Creutzfeldt–Jakob disease yielded a specificity of 100% (95% CI, 90 to 100).

RT-QuIC Analysis of Cerebrospinal Fluid

In contrast to the results of RT-QuIC analysis of olfactory mucosa samples, RT-QuIC analysis of cerebrospinal fluid samples had a sensitivity of 77% (95% CI, 57 to 89), with 23 RT-QuIC–positive reactions in 30 samples from patients with sporadic Creutzfeldt–Jakob disease, and a specificity of 100% (95% CI, 90 to 100), with 46 RT-QuIC–negative reactions in 46 samples from patients without Creutzfeldt–Jakob disease (Figure 1 and Table 1 and Table 2, and Fig. S4 in the Supplementary Appendix); these results were similar to those in previous studies.16,17 For four of the patients with Creutzfeldt–Jakob disease, cerebrospinal fluid was obtained twice, as indicated in Table 1 and Figure 1; however, only the RT-QuIC results from the cerebrospinal fluid sample that was obtained closest in time to the olfactory mucosa collection are included in Table 2 and were used to calculate the RT-QuIC sensitivity. The olfactory mucosa pellets in 1:250 dilutions became positive much more rapidly than all but one of the undiluted cerebrospinal fluid samples from the same patients (Figure 1A, and Fig. S4A through S4N in the Supplementary Appendix). In addition, the mean relative ThT fluorescence at our designated cutoff time (50 hours for olfactory mucosa and 90 hours for cerebrospinal fluid) was significantly higher in the olfactory mucosa samples than in the cerebrospinal fluid samples (P<0.001 with the use of an unpaired t-test) (Figure 1B).

Seed Concentrations in Samples from Patients with Sporadic Creutzfeldt–Jakob Disease

End-point dilution RT-QuIC analysis18 of olfactory mucosa pellets (7 samples), brain-tissue samples (12), and cerebrospinal fluid samples (2) indicated that the concentrations of seeding doses resulting in 50% ThT-positive replicate reactions (SD50) for these samples were 3.4 to 4.1 log10 SD50 per microliter of packed olfactory mucosa pellets, 7.2 to 8.95 log10 SD50 per milligram of brain tissue, and 0.2 to 0.5 (i.e., <0.1 log10) SD50 per microliter of cerebrospinal fluid. Thus, the seeding concentrations for olfactory mucosa were intermediate between those for cerebrospinal fluid and those for brain tissue. Considering that the olfactory mucosa brush specimens yielded packed pellets of more than 50 μl, the total number of Creutzfeldt–Jakob disease prion seeds captured by individual brushings ranged from approximately 105 to 107.

Discussion

The high sensitivity and specificity of RT-QuIC testing of nasal brushings in identifying patients with Creutzfeldt–Jakob disease indicate that this procedure has the potential to be useful for establishing a definitive diagnosis of Creutzfeldt–Jakob disease in living patients. Olfactory mucosa samples gave significantly stronger RT-QuIC responses than cerebrospinal fluid samples obtained from the same patients, and the RT-QuIC responses were obtained in less time (50 hours vs. 90 hours) (Figure 1, and Fig. S4 in the Supplementary Appendix). Moreover, to date, the overall sensitivity of the olfactory mucosa–based RT-QuIC test for the diagnosis of sporadic Creutzfeldt–Jakob disease appears to be higher than that of the cerebrospinal fluid–based RT-QuIC test in the same patients. However, other studies have shown somewhat higher sensitivities for the RT-QuIC test of cerebrospinal fluid16,17 than those obtained in this study. In any case, further validation of both the olfactory mucosa–based test and the cerebrospinal fluid–based test is needed to fully establish their relative diagnostic sensitivities and specificities in clinical settings and to determine how early seeding activity can be detected in the course of Creutzfeldt–Jakob disease. Furthermore, in six of seven patients with sporadic Creutzfeldt–Jakob disease in whom the RT-QuIC test of cerebrospinal fluid was negative but the RT-QuIC test of olfactory mucosa was positive, the lumbar puncture and olfactory mucosa brushing were performed at almost the same interval after disease onset, suggesting that the observed differences in prion seeding activity between these specimens were not due to differences in sampling time.

Although cerebrospinal fluid samples are likely to be obtained from most patients with rapidly progressing dementia to rule out other treatable disorders, RT-QuIC testing of olfactory mucosa may prove to be more accurate than RT-QuIC testing of cerebrospinal fluid for the detection of Creutzfeldt–Jakob disease. In our study, all the patients with suspected sporadic Creutzfeldt–Jakob disease fulfilled the diagnostic criteria for probable or possible sporadic Creutzfeldt–Jakob disease at the time of olfactory mucosa brushing, including the two patients with a negative family history of dementia who subsequently received a diagnosis of inherited (E200K) Creutzfeldt–Jakob disease.

In sporadic Creutzfeldt–Jakob disease, clinical variants are linked to the M/V polymorphism at PrP residue 129, combined with the PrPCJD type 1 or 2. These molecular factors appear to influence PrP conversion and accumulation kinetics in vivo and in some in vitro reactions, such as protein misfolding cyclic amplification (PMCA).27 However, with RT-QuIC reactions that use the hamster rPrPSen substrate, each of the subtypes of sporadic Creutzfeldt–Jakob disease is readily detectable, as observed with RT-QuIC analysis of cerebrospinal fluid samples.16 Although the molecular basis for the broad convertibility of this substrate is not yet clear, if it can be widely replicated it will provide the practical advantage of requiring only a single test with a single substrate to screen for the full spectrum of sporadic Creutzfeldt–Jakob disease phenotypes.

The high seeding activity of sporadic Creutzfeldt–Jakob disease in olfactory mucosa suggests that infectivity may be present as well, posing biosafety implications. The multiple logs10 of prion seeds that we have detected in the nasal vault lining of patients with sporadic Creutzfeldt–Jakob disease raise the possibility that sporadic Creutzfeldt–Jakob disease prions could contaminate nasal discharges. Nasal and aerosol-borne transmission of prion diseases have been documented in animal models,28-32 but there is no epidemiologic evidence for aerosol-borne transmission of sporadic Creutzfeldt–Jakob disease. Moreover, although prion infectivity and RT-QuIC seeding activity have been detected in nasal lavages from prion-infected hamsters,33,34 no transmission was apparent in nonhuman primates injected with human spongiform encephalopathy nasal mucus.35 However, medical instruments that come into contact with the olfactory mucosa of humans with Creutzfeldt–Jakob disease might become contaminated with prions, which poses the question of whether iatrogenic transmission is possible.36,37 Therefore, further study of possible biohazards posed by prions in the olfactory mucosa is warranted.

Funding and Disclosures

Supported by the Intramural Research Program of the National Institute of Allergy and Infectious Diseases (NIAID), by a grant from Fondazione Cariverona (Disabilità cognitiva e comportamentale nelle demenze e nelle psicosi, to Dr. Monaco), by a grant from the Italian Ministry of Health (RF2009-1474758, to Drs. Zanusso and Pocchiari), by a grant from the Creutzfeldt–Jakob Disease Foundation (to Dr. Orrú), by a fellowship from Programma Master and Back–Percorsi di rientro (PRR-MAB-A2011-19199, to Dr. Orrú), and by donations to the NIAID Gift Fund from Mary Hilderman Smith, Zoë Smith Jaye, and Jenny Smith Unruh, in memory of Jeffrey Smith.

Disclosure forms provided by the authors are available with the full text of this article at NEJM.org.

Drs. Orrú and Bongianni contributed equally to this article.

This article was updated on November 6, 2014, at NEJM.org.

We thank our many colleagues (see Acknowledgments in the Supplementary Appendix) for their support of this project and for assistance with the preparation of earlier versions of the manuscript.

Author Affiliations

From the Laboratory of Persistent Viral Diseases, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases (NIAID), National Institutes of Health, Hamilton, MT (C.D.O., M.B., A.G.H., B.R.G., B.C.); and the Department of Biomedical Sciences, University of Cagliari, Cagliari (C.D.O.), the Department of Neurologic and Movement Sciences, University of Verona, Verona (M.B., S.F., M.F., S.M., G.Z.), Clinica Otorinolaringoiatrica, Policlinico G.B. Rossi, Azienda Ospedaliera Universitaria Integrata, Verona (G.T.), and the Department of Cell Biology and Neurosciences, Istituto Superiore di Sanità, Rome (M.P.) — all in Italy.

Address reprint requests to Dr. Caughey at Rocky Mountain Laboratories, NIAID, 903 S. 4th St., Hamilton, MT 59840, or at ; or to Dr. Zanusso at Policlinico G.B. Rossi, Piazzale L.A. Scuro, 10, 37134 Verona, Italy, or at .

Supplementary Material

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    1. Table 1. Demographic Characteristics, Clinical Profiles, Diagnostic Factors, and Real-Time Quaking-Induced Conversion (RT-QuIC) Analyses of Patients with Creutzfeldt–Jakob Disease.
      Table 1. Demographic Characteristics, Clinical Profiles, Diagnostic Factors, and Real-Time Quaking-Induced Conversion (RT-QuIC) Analyses of Patients with Creutzfeldt–Jakob Disease.
    2. Table 2. Results of RT-QuIC Assays of Olfactory Mucosa and Cerebrospinal Fluid Samples.
      Table 2. Results of RT-QuIC Assays of Olfactory Mucosa and Cerebrospinal Fluid Samples.
    3. Figure 1. Results of Real-Time Quaking-Induced Conversion (RT-QuIC) Assays of Olfactory Mucosa (OM) and Cerebrospinal Fluid (CSF) Samples.
      Figure 1. Results of Real-Time Quaking-Induced Conversion (RT-QuIC) Assays of Olfactory Mucosa (OM) and Cerebrospinal Fluid (CSF) Samples.

      Panel A shows the average percent thioflavin T (ThT) fluorescence readings from four replicate reactions (normalized as described in the Methods section), determined in samples of OM and CSF from patients with possible, probable, or definite Creutzfeldt–Jakob disease and from controls without Creutzfeldt–Jakob disease. The means (thick lines) with standard deviations (thin lines) of those averages are shown as a function of RT-QuIC reaction time. Panel B shows the final average relative ThT fluorescence readings for each person with Creutzfeldt–Jakob disease (CJD) and for each control with either a neurologic disease other than Creutzfeldt–Jakob disease (other neurologic disease [OND]) or no neurologic disease (NND) at either 50 hours (OM samples) or 90 hours (CSF samples). Inherited CJD refers to patients with the E200K PRNP genetic mutation causing CJD. All OM and CSF samples obtained from patients with CJD and from controls are reflected in these data. The total number of CSF samples from patients with CJD (34) does not include a sample from one patient (Patient 31; CSF not tested) and includes results from two lumbar punctures each in four patients with CJD.

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