Patent Publication Number: US-2006008494-A1

Title: Complete inactivation of infectious proteins

Description:
CROSS-REFERENCE  
      This application claims priority to provisional Application Ser. No. 60/618,115, filed Oct. 12, 2004 which claims priority to provisional Application Ser. No. 60/581,921, filed Jun. 21, 2004 and is a continuation-in-part application of U.S. application Ser. No. 10/735,454, filed Dec. 12, 2003, which application is a continuation of U.S. application Ser. No. 10/056,222, filed Jan. 22, 2002 now U.S. Pat. No. 6,720,355 issued Apr. 13, 2004, which is a continuation-in-part of U.S. application Ser. No. 09/904,178, filed Jul. 11, 2001 now U.S. Pat. No. 6,719,988 issued Apr. 13, 2004, which is a continuation-in-part of U.S. application Ser. No. 09/699,284, filed Oct. 26, 2000 now abandoned, which is a continuation-in-part of U.S. application Ser. No. 09/494,814, filed Jan. 31, 2000, now U.S. Pat. No. 6,322,802, which is a continuation-in-part of U.S. application Ser. No. 09/447,456, filed Nov. 22, 1999 now U.S. Pat. No. 6,331,296, and also is a continuation-in-part of U.S. application Ser. No. 09/406,972, filed Sep. 28, 1999 now U.S. Pat. No. 6,419,916, both of which are a continuation-in-parts of U.S. application Ser. No. 09/322,903, filed Jun. 1, 1999, now U.S. Pat. No. 6,214,366 and to which priority is claimed under 35 U.S.C. §§ 120 and 119. This application is also a continuation-in-part of U.S. application Ser. No. 09/235,372, filed Jan. 20, 1999, now U.S. Pat. No. 6,221,614, issued Apr. 24, 2001, which is a continuation-in-part of U.S. application Ser. No. 09/151,057, filed on Sep. 10, 1998, now abandoned, which is a continuation-in-part of U.S. application Ser. No. 09/026,957, filed on Feb. 20, 1998, now abandoned, which is a continuation-in-part of U.S. application Ser. No. 08/804,536, filed on Feb. 21, 1997, now U.S. Pat. No. 5,891,641, all of which applications are incorporated herein by reference and to which applications priority is claimed under 35 U.S.C. §§ 120 and 119. The current disclosure is controlling to the extent it conflicts with an earlier disclosure.  
    
    
     GOVERNMENT RIGHTS  
      This invention was made with government support under federal grant nos. AG02132, AG08967, AG10770, NS02048, and NS14069 awarded by The National Institutes of Health. The United States Government may have certain rights in this invention. 
    
    
     FIELD OF THE INVENTION  
      This invention relates generally to the field of disinfectants and more particularly to disinfectants for inactivating the infectivity of infectious proteins.  
     BACKGROUND OF THE INVENTION  
      The prion diseases including Creutzfeldt Jakob Disease (CJD) in humans, bovine spongiform encephalopathy (BSE) in cattle, and scrapie in sheep are fatal neurodegenerative illnesses caused by infectious pathogens designated prions. More than 200 documented cases of iatrogenic CJD have been caused by inadequate disinfection of pituitary extract-derived hormone supplements, dura mater and corneal grafts, and neurosurgical equipment. Epidemiological evidence suggests that CJD might also be transmitted by surgical procedures outside the CNS. Conventional hospital disinfectants including ethylene oxide, propriolactone, hydrogen peroxide, iodophors, peractic acid, chaotropes and phenolics have little effect on prion infectivity. In addition, infectious prions are resistant to UV irradiation, aldehyde fixation, boiling, standard gravity autoclaving at 121° C., and detergent solubilization.  
      Currently recommended protocols for prion decontamination include either: (i) &gt;2% available chlorine of sodium hypochlorite for 2 h, (ii) 2 M sodium hydroxide for 1 h, or (iii) autoclaving at 134° C. for 4.5 h. Each of these protocols has important limitations: sodium hypochlorite is corrosive at the concentrations required to inactivate prions; sodium hydroxide is also corrosive and does not inactivate CJD prions completely; autoclaving is time-consuming, cannot be used with heat-sensitive or complex materials, and generates dried macerated tissue resistant to inactivation. Because of these limitations, prion decontamination of surgical or dental equipment is performed only after operations on patients suspected to have CJD. Standard protocols used to sterilize instruments following operations on all other patients, such as routine autoclaving or bath sonication, do not inactivate prions. Therefore, a practicable method for routine prion decontamination of all surgical instruments is urgently needed to prevent cases of iatrogenic CJD resulting from failure to suspect prion disease in surgical or dental patients.  
      The anionic (negatively charge) detergent sodium dodecyl sulfate (SDS) is a particularly attractive candidate for use as a surface prion disinfectant because it is (1) denaturing to prions under certain conditions, (2) non-corrosive to metals, and (3) inexpensive. However, previous attempts to disinfect prions with neutral solutions of SDS yielded mixed results. In some experiments, 3% SDS at neutral pH reportedly destroyed prion infectivity in brain homogenates when samples were boiled or autoclaved. In other experiments, boiling brain homogenates in 2% SDS at neutral pH did not substantially reduce prion infectivity. Furthermore, prion infectivity in macerated brain samples survived boiling for 15 min in 5% SDS at neutral pH. This evidence suggests that SDS solutions at neutral pH, even at high temperatures, cannot be used reliably for prion decontamination.  
     SUMMARY OF THE INVENTION  
      The invention comprises a formulation and a method which uses the formulation. The formulation is comprised of an aqueous or alcohol solvent having therein (1) a detergent such as SDS; (2) a weak acid such acetic acid; and (3) chemical modification reagent such as hydrogen peroxide. The formulation can be modified to substitute other detergents for the SDS and other acids for the acetic acid provided the substitute results in a total formulation which completely inactivates the infectivity of infectious proteins such as prions in a relatively short period of time (e.g. less than two hours) and under relatively mild temperatures (e.g. 60° C. or less) and a relatively mild pH range of about 2.5 to 4.0.  
      An aspect of the invention is the chemical modification reagent, which is any chemical that covalently modifies one or more of the side chains of amino acids in an infectious protein such as prions. Hydrogen peroxide and peracetic acid are examples of such chemical reagents that oxidize amino acid side chains.  
      An aspect of the invention is that it is comprised of relatively low concentration of relatively common and inexpensive components.  
      An aspect of the present invention is a mixture of the cationic detergent CTAB and other detergents, with an oxidizing reagent such as peracetic acid in concentrations and proportions which denature PrP Sc  completely in a short period of time under mild conditions. Mixtures and/or solutions of the invention provide a non-corrosive and yet a more robust prion disinfectant suitable for routine use in surgical decontamination, animal rendering, and related fields.  
      The formulation of the invention may be comprised of, consist of, or consist essentially of a detergent, a weak acid and a chemical modification reagent and a solvent. The detergent is preferably sodium dodecyl sulfate (SDS) or cetylmethylammonium bromide (CTAB). It should be noted that SDS can be referred to as sodium dodecyl sulfinate which is a twelve carbon alkyl salt of sulfonic or sulfuric acid. The weak acid component may be an acid such as acetic acid or peracetic acid which maintains the pH at about 4.0 or less or in a range of about 2.5 to 4.0. It is desirable to maintain the pH below 4.0 but not to reduce the pH so low such that when the formulation is used on metal surfaces such as surgical instruments it causes damage to those instruments. The composition may include a solvent such as water or alcohol and the chemical modification reagent may be hydrogen peroxide which may be liquid, gaseous, or in a plasma form.  
      The method of the invention applies the formulation to surfaces which may be infected with infectious proteins such as prions and results in the complete inactivation of those proteins. The method comprises contacting the infectious protein such as prions with a formulation of the invention for a period of time and under conditions so as to completely inactivate the infectivity of the protein. An important aspect of the invention is to completely inactivate the infectivity of the proteins in a relatively short period of time, e.g. 2 hours or less, or 1 hour or less. Another aspect of the invention is the inactivation of the infectious protein such as prions under relatively mild conditions such as at a temperature, pH and other conditions which do not adversely effect surfaces such as medical devices and surgical components which might be contacted with the formulation in order to inactivate infectious proteins present on their surfaces. Thus, the temperature may be relatively high such as approximately 130° C. to 140° C. used in autoclaving but may be relatively low such as less than 100° C. or even less than 80° C. or less than 60° C. and still obtain the objects of the invention which include complete inactivation of the infectious proteins. Further, the pH may be relatively low but can be in a range of about 2.5 to 4.0 and still achieve the objects of the invention of complete prion inactivation.  
      These and other objects, advantages, and features of the invention will become apparent to those persons skilled in the art upon reading the details of the formulation and method as more fully described below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention is best understood from the following detailed description when read in conjunction with the accompanying drawings. It is emphasized that, according to common practice, the various features of the drawings are not to-scale. On the contrary, the dimensions of the various features are arbitrarily expanded or reduced for clarity. Included in the drawings are the following figures:  
       FIG. 1  is a graph of the percent survival versus incubation time in days.  
       FIG. 2  includes  FIG. 2A  showing an image of gels over a range of different pHs and  FIG. 2B  showing gels as described further within Example 2 and  FIG. 2C  showing gels with and without acetic acid as described further in Example 2.  
       FIG. 3  includes  FIG. 3A  showing gels or different formulations were applied and to the different lanes as described further within Example 3 with a bar graph of the results shown in  FIG. 3B .  
       FIG. 4  includes  FIG. 4A  showing a gel with film exposed for 15 seconds and  FIG. 4B  showing the film exposed for 10 minutes as described further within Example 4.  
       FIG. 5  includes two gels with the lanes described at the bottom of  FIG. 5  and a further description provided within Example 5.  
       FIG. 6  includes the gel of  FIG. 6A  and the resulting bar graph of  FIG. 6B  with the Figures described further within Example 6.  
       FIG. 7  includes a six lane gel with the different formulations used as shown in the description at the bottom of  FIG. 7  with the image further described within Example 7.  
       FIG. 8  includes an image of 14 lanes exposed to different formulations described at the bottom of  FIG. 8  with a further description provided within Example 8.  
       FIG. 9  includes two gels of five lanes each using different antibodies as described within Example 9.  
       FIG. 10  includes the gel of  FIG. 10A  and gel of  FIG. 10B  as described further within Example 10.  
       FIG. 11  includes two gels as described further within Example 11. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      Before the present method and formulations are described, it is to be understood that this invention is not limited to particular embodiments described, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only, and is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.  
      Where a range of values is provided, it is understood that each intervening value, to the tenth of the unit of the lower limit unless the context clearly dictates otherwise, between the upper and lower limits of that range is also specifically disclosed. Each smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in that stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range, and each range where either, neither or both limits are included in the smaller ranges is also encompassed within the invention, subject to any specifically excluded limit in the stated range. Where the stated range includes one or both of the limits, ranges excluding either or both of those included limits are also included in the invention.  
      Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, the preferred methods and materials are now described. All publications mentioned herein are incorporated herein by reference to disclose and describe the methods and/or materials in connection with which the publications are cited.  
      It must be noted that as used herein and in the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to “a detergent” includes a plurality of such detergents and reference to “the acid” includes reference to one or more acids and equivalents thereof known to those skilled in the art, and so forth.  
      The publications discussed herein are provided solely for their disclosure prior to the filing date of the present application. Nothing herein is to be construed as an admission that the present invention is not entitled to antedate such publication by virtue of prior invention. Further, the dates of publication provided may be different from the actual publication dates which may need to be independently confirmed.  
     Invention in General  
      The invention relates to formulations and methods for inactivating the infectivity of infectious proteins such as prions. The invention results in total or complete inactivation of the infectious nature of the protein such as prions or PrP Sc  and does so under mild pH and temperature conditions. Thus, the formulations and methods can be used in a wide range of environments without having destructive or damaging effects on the instruments or environments contacted with a formulation of the invention. The formulation may be comprised of multiple components. A typical formulation is comprised of a solvent such as water and/or alcohol such as methanol or ethanol having three active components therein. The three active components are, for example, (1) a detergent such as sodium dodecyl sulfate (SDS) and/or cetylmethylammonium bromide (CTAB); (2) a weak acid such as acetic acid or peracetic acid; and (3) a chemical modification reagent such as hydrogen peroxide. The active components may be applied together or sequentially with the detergent applied first.  
      The invention may be in the form of a method of disinfecting which method may use the formulation or may use individual components of the formulation in sequence. For example, the detergent may be applied to the protein such as prions. Thereafter, the weak acid is applied. Thereafter the chemical modification reagent is applied. Each step may be carried out under relatively mild conditions, e.g. a temperature in a range of about 10° C. to about 80° C. or 15° C. to 60° C. for two hours or less for each step or for all the steps combined.  
      In connection with either the method or the formulation of the invention results may be obtained using the detergent with only the weak acid or with only the chemical modification reagent. However, results are improved when all three components are used.  
      Without relying on a particular theory or mechanism of action it is believed the formulations of the invention operate on infectious proteins such as prions by (1) causing a change in the protein&#39;s conformation, i.e. the manner in which the chain of amino acids fold; and (2) chemically modifying one or more amino acids in the chain resulting in a modified chain which is incapable of refolding into its infectious conformation. Although the active components may interact to obtain these results the detergent is generally changing the initial conformation and the acid and/or the peroxide are generally responsible for chemically altering one or more of the amino acids.  
     Infectious Proteins  
      Farm animals in United Kingdom were fed meat and bone meal during the BSE epidemic. Accordingly, the possibility that BSE may have passed to flocks of sheep and goats is a real concern. If BSE has been transmitted to sheep, this could pose serious risk to humans and livestock since BSE prions seem capable of infecting a broad range of mammal species. More tissues are infectious in sheep than in cattle, and prions seem to spread within the sheep population without much difficulty. In order to determine whether BSE has been passed to sheep, homogenate from sheep experimentally infected with BSE prions were passaged to mice. This resulted in an incubation time and lesion profile similar to those caused by homogenates of cattle with BSE. However, large-scale screening of tens of thousands of sheep by this approach seems unpractical. The inventive results provided here show that a formulation of SDS and peroxygenic compounds at low pH can discriminate between some strains of the same species. Differences could be discriminated in western blot and ELISA setting using antibodies against residues 95-112. This finding shows that other prions strains including scrapie and BSE in sheep can be discriminated using this approach.  
      The present invention shows that chemical modification reagents such as oxidizing agents boost the denaturation effect of SDS at low pH. Combinations of these three components are more potent than any two at denaturing PrP Sc . Peracetic acid and hydrogen peroxide are currently used as general microbial disinfectant [Rutala, W. A. (1996). “APIC guideline for selection and use of disinfectants.”  Amer. J. Infect. Control  24: 313-342]. A combination of these two compounds with acidic SDS provides a very broad spectrum of disinfecting activity. Addition of metal ions promotes the formation of hydroxyl radical and antimicrobial activity, and therefore, further enhances denaturation of PrP Sc . This finding shows that effective denaturation of PrP Sc  is achieved at temperatures suitable for heat sensitive devices.  
      The anionic detergent SDS at low pH will denature PrP Sc . To confirm that denaturation of PrP Sc  caused by acidic SDS correlates with reduction in prion infectivity, Sc237-infected SHa brain homogenates were incubated for 2 h in different buffer conditions at various temperatures to provide treated samples that were injected intracerebrally into indicator Syrian hamsters. Inoculation of a control brain homogenate sample containing 10 7  ID 50  units Sc237 prions/ml at neutral pH without detergent caused scrapie in 16 of 16 indicator animals in 79±1 days. The results are plotted in the solid triangles of  FIG. 1 . Indicator animals inoculated with parallel samples exposed to either 0.5% acetic acid or 1% SDS alone at 37° C. developed scrapie in 82±1 and 91±2 days, respectively. These results are shown respectively by the solid circles and open triangles of  FIG. 1 . In contrast, exposure of the inoculum to a combination of 0.5% acetic acid and 1% SDS for 2 h at 37° C. prolonged the mean scrapie incubation time to 210±12 days. This data is plotted in  FIG. 1  with the open circles. Decreasing the incubation temperature for exposure to acidic SDS to 20° C. resulted in a mean scrapie incubation time of ˜175 days and this data is plotted in  FIG. 1  with the solid squares. These data suggest that acidic SDS at room temperature or 37° C. will not be effective in eliminating all prion infectivity. However, there is clearly a need to develop a safe and effective means for more robust inactivation of prions in settings were high temperature and/or extreme pH conditions are not an option.  
      The oxidizing solution hydrogen peroxide (HP, H 2 O 2 ) by itself does not disinfect prions [Brown, P., R. G. Rohwer, et al. (1982). “Effect of chemicals, heat, and histopathologic processing on high-infectivity hamster-adapted scrapie virus.”  J. Infect. Dis.  145: 683-687]. Consistent with this it is pointed out that H 2 O 2  does not denature PrP Sc . The present invention show that H 2 O 2  by itself under mild conditions in the presence of SDS at low pH effectively denatures PrP Sc  rendering them completely non-infectious under mild conditions. Hydrogen peroxide is also effective in killing and/or inactivating a wide range of organisms: bacteria, yeast, fungi, viruses, and spores. Peroxygen compounds.  Disinfection, Sterilization, and Preservation.  S. S. Block. Philadelphia, Lippincott Williams &amp; Wilkins: 185-204 (2001)]. The present invention shows that oxidizing reagents and acidic SDS act synergistically to denature prions rendering them completely non-infectious under mild conditions. Further, the present invention shows that the combination of acidic SDS and oxidizing reagents possess a very broad spectrum of disinfecting activity.  
      Acidic SDS and Hydrogen Peroxide Synergies to Denature PrP Sc    
       FIG. 2A  provides immunoblots showing that aqueous solutions of ≧1% SDS denature PrP Sc  completely at pH values ≦4.5 or ≧10.0 following limited proteolysis.  FIG. 2C  shows that other detergents at low pH do not denature PrP Sc . Acidic buffers other than acetic acid synergize with SDS to denature PrP Sc . Samples of Sc237-infected SHa brain homogenates were incubated with 1% SDS plus 0.5% acetic acid, pH 3.6; 50 mM glycine, pH 3.7; or 0.2% peracetic acid, pH 3.4 for 15 min at 37° C. The results in the immunoblots of  FIG. 2B  show that PrP Sc  was denatured in the presence of each of these acidic buffers.  
      The Western blot ELISA of  FIG. 3A  and bar graph of  FIG. 3B  shows that 0.2% peracetic acid (PAA) and 4% SDS is three times more effective in denaturating PrP Sc  as compared to 1% acetic acid and 4% SDS following limited proteolysis (compare lanes  2  and  3 ). This is a surprising result since both SDS solutions are at low pH. As peracetic acid (PAA) is formed by addition of reactive oxygen to acetic acid by H 2 O 2  these results show that oxidation of PrP Sc  augments its denaturation by acidic SDS. The reaction of acetic acid to peracetic acid is shown below.  
                 
 
      The effect of the oxidizer hydrogen peroxide (H 2 O 2 ) on Sc237-infected SHa brain homogenates at room temperature was examined. It was found that 10% HP does not denature PrP Sc  and these results are shown in lane  1  of  FIG. 3A . This is consistent with previous study where treatment with 3% HP was not shown to diminish prion infectivity [Brown, P., R. G. Rohwer, et al. (1982). “Effect of chemicals, heat, and histopathologic processing on high-infectivity hamster-adapted scrapie virus.”  J. Infect. Dis.  145: 683-687]. However, a comparison of lanes  1  and  2  of  FIG. 3B  shows that the combination of both acetic acid and SDS (4% SDS, 1% acetic acid) do denature PrP Sc . Further,  FIG. 3B  lane  4  shows that 10% HP in the presence of 1% acetic acid does not denature PrP Sc  either. Further, lanes  5 ,  7  and  9  of  FIG. 3B  show that a solution formulation of 4% SDS, 1% acetic acid and 2.5-10% HP was highly effective in denaturating PrP Sc . A mixture of acidic SDS and oxidizing reagent is a more efficient denaturant as compared to any of these acidic SDS solutions ( FIG. 3B ; compare lane  2  to lanes  3 ,  5 ,  7 , and  9 ). These results shown in  FIGS. 3A and 3B  indicate that combination of (1) oxidizing reagents; (2) acetic acid; and (3) SDS synergizes to denature PrP Sc  and therefore are more effective than the combination of acetic acid and SDS.  
       FIG. 4  shows the results of another set of experiments carried out to determine the efficacy of different formulations of acetic acid, SDS, and peroxygen compounds at room temperature. These results show that formulations of SDS and acetic acid were a more effective denaturant as compared to any of: 1) hydrogen peroxide (HP), 2) HP/acetic acid, 3) HP/SDS, and 4) PA ( FIG. 4A  compare lanes  2 ,  4 ,  5 , and  7 , respectively). Treatment with a mixture of oxidizing reagents; HP/PA was more effective than acidic SDS, but some residual PrP Sc  was detected ( FIG. 4A  lanes  2  and  9 ). Mixtures of SDS and oxidizing compounds (PA and HP) at low pH are clearly more effective as compared to SDS at low pH ( FIG. 4A  compare lanes  6 ,  8 , and  10  to lane  2 ). Of the tested formulations the combination SDS, peracetic acid and HP was shown to be the most potent denaturant ( FIG. 4B  lane  10 ).  
     Examples of Active Components  
      In addition to the detergent there is an active component of the invention which may be either or both of a chemical modification reagent and a weak acid such as acetic acid and peracetic acid. Other acids such as perfomic acid, iodoacetic acid, nitrous acid, p-sulfondichloramindobenzoic acid, trichloro-isocyanuric acid, and dichloro-isocyanuric acid can be used. The acid should be present in an amount and molarity so as to maintain the pH of the formulation in a range of about 5.0 to about 3.0, or less than about 4.0. In another embodiment the acid may be replaced with a base component present in an amount and molarity to obtain a pH of the formulation of about 9.0 or more, or about 8.0 to about 10.0.  
      The third active component is the chemical modification reagent. Such may be hydrogen peroxide added as a liquid, gas or plasma. However, a list of useful chemical modification reagents is provided below:  
               TABLE 1                       Chemical modification reagents                                            Hydrogen Peroxide           N-Succinimdyl propionate           Diethylpyrocarbonate           Formaldehyde           Glutaraldehyde           Iodine           Maleic anhydride           Dithiothreitol (DTT)           Sodium borohydride           Succinic anhydride           Acetic anhydride           Maleic anhydride           Sulfonyl halides           Carbodiimide           Diazonium salts           Iodoacetate           Sulfites           Phosphorothioate           5,5′-Dithiobis(2-Nitrobenzoic acid) (DTNB)           Iodosobenzoate           Tetrathionate           N-bromosuccinamide (NBS)           N-bromoacetamide           Tetranitromethane           Cyanogen bromide           Hypochlorites           Chlorinated trisodium phosphate           Chlorine dioxide           N,N′-dichloroazodicarbonamidine           Sulfonchloramide           Succinchlorimide           1,3-Dichloro-5,5-dimethylhydantoin           Trichloromelamine           Ozone           Chlorine           Phenylglyoxal           Nitriles           Pyridines           Thiazoles           Ortho-phthaldehyde           Nitric oxide           Beta-propiolactone           N-ethylmaleimide                      
 
 H 2 O 2  and Detergents 
 
      Further experiments were carried out to show the efficacy of HP and other detergents in denaturating PrP Sc . In the experiment Sc237-infected SHa brain homogenates were incubated with one of: A) 2% detergent, B) 2% detergent and 5% HP, C) 2% detergent, 5% HP and 1% acetic acid, and D) 2% detergent and 1% acetic, for 30 min at room temperature. Images of Western Blots of the results are shown in  FIG. 5 . Acidic SDS denatures most of the PrP Sc , but some residual PrP Sc  remains as shown in the Western blot of  FIG. 5 —compare lanes A, B to lane D. Addition of 5% HP to acidic SDS eliminates all PrP Sc  as judged by western blotting after limited proteinase K digestion ( FIG. 5 , SDS; lane C). In contrast, HP and the detergents Triton X100, Sarkosyl, CTAB, Cholic acid, and Zwittergent each fail to denature PrP Sc  effectively in any of these conditions ( FIG. 5 ). These results show that the synergistic effect of H 2 O 2  is specific to SDS at low pH.  
      Formulation of Various Detergents and Peracetic Acid Denature PrP Sc    
      Additional experiments were carried out to show whether the formulation of peracetic acid with detergents other than SDS would denature PrP Sc . In the experiments Sc237-infected SHa brain homogenates were incubated with various detergents, with or without 0.2% peracetic acid, for 30 min at room temperature.  FIGS. 6A and 6B  show that peracetic acid with SDS denatures PrP Sc  in 30 min under these conditions, as judged by Western blot and ELISA following limited proteolysis. There was no detection of PrP Sc  after treatment with the cationic detergent CTAB combined with peracetic acid. The levels of PrP Sc  were also reduced in homogenates treated with 0.2% peracetic acid and the detergents Cholic acid, Deoxycholic acid, Triton X100, NP40, Tween 20, Zwittergent and CHAPS (See  FIGS. 6A and 6B , paired lanes  2  to  9 , respectively). These finding show that in the presence of peracetic acid the most potent detergents in denaturating PrP Sc  are SDS and CTAB.  
      Denaturation Efficacy of CTAB and Peroxygenic Solutions  
      Further experiments were carried out to more thoroughly test the effect of CTAB on PrP Sc  at oxidizing conditions. Prion infected brain homogenate were treated with formulations of: 1) CTAB, 2) CTAB and H 2 O 2 , and 3) CTAB, H 2 O 2  and acetic acid. The results are shown in  FIG. 7  in lanes  2 ,  3 ,  4  respectively showing little effect on PrP Sc  as judged by Western blotting after limited proteolysis. Formulations of CTAB at low pH with peracetic acid or H 2 O 2  were clearly effective in denaturating PrP Sc  as shown in lanes  5  and  6  of  FIG. 7 .  
      Prion Strain Discrimination With Peroxygen and Acidic SDS  
      Additional experiments were carried out where Sc237-infected Syrian hamster brain homogenate Sc237 was treated with increasing concentrations of peracetic acid. The results of  FIG. 8  show a progressive decrease in the levels of PrP Sc  as judged by Western blotting after limited proteolysis. Treatment with 0.2% peracetic acid in the presence of 4% SDS results in stronger denaturation of PrP Sc . The results show that a formulation of 0.2% peracetic acid and SDS is a stronger denaturant than 0.6% peracetic.  
      PrP Sc  is resistant to proteolysis except for the N-terminal region comprising ˜67 residues (Caughey, B. and G. J. Raymond (1991) “The scrapie-associated form of PrP is made from a cell surface precursor that is both protease- and phospholipase-sensitive.”  J. Biol. Chem.  266:18217-18223; Gasset, M., M. A. Baldwin, et al. (1993). “Perturbation of the secondary structure of the scrapie prion protein under conditions that alter infectivity.”  Proc. Natl. Acad. Sci. USA  90: 1-5.). The protease-resistant fragment of Sc237 PrP Sc  has a molecular size of 27-30 kDa and is designated PrP 27-30 [Prusiner, S. B. (1983). On the molecular structure of the scrapie agent.  Unconventional Viruses and the Central Nervous System.  L. A. Court and F. Cathala. Paris, Masson Editeur: 57-83]. It consists of ˜142 amino acids (residues 90-231) and conveys prion infectivity. Indeed, when prion infected brain homogenates are treated with SDS or various detergents at low pH, the main residual protease-resistant fragment of Sc237 PrP Sc  has a molecular weight of 27-30k. Sc237 PrP Sc  incubated with H 2 O 2  or peracetic at low pH and treated with proteinase K also has a molecular weight of 27-30 kDa as shown in  FIGS. 4A and 4B . The results of  FIG. 8  show that treatment of prion infected brain homogenates with SDS and oxidizing reagents at low pH, followed by limited proteolysis by proteinase K digestion, results in a residual protease resistant fragment with a molecular weight of ˜22 kDa. This fragment is shown in lane  10 - 14  of  FIG. 8 . Evidence of this fragment can also be seen in  FIG. 3A  lane  9 ,  FIG. 4  lanes  6 ,  8 ,  10  and  FIG. 6A  lane paired lanes  1 .  
      In order to determine the epitope which was denatured Sc237 brain homogenates were treated first with SDS and peracetic acid, followed by PK digestion. Thereafter tests were carried out for the presence of PrP Sc  in ELISA with a battery of recombinant Fab antibodies recognizing different epitopes. The following Fabs were used: D13 (epitope; 95-103), 3F4 (epitope; 109-112), 13A5 (epitope; 138-141) D18 (epitope; 133-157), R72 (epitope; 151-162), R1 (epitope; 220-231), and R2 (epitope; 225-231). All samples tested positive for PrP Sc  except for those with D13 and 3F4. When these brain homogenates samples were tested with western blotting PrP Sc  was clearly detected with D18 but not with 3F4 as shown in  FIG. 9 . These results show that residues at the N-terminus (at least 90-112) show greater sensitivity to denaturation (compared to the rest of the protease resistant fragment) when acted upon by a combination of acidic SDS and peroxygen compounds.  
      Further experiments were carried out in order to determine whether different strains of prion strains, which contain different conformations of PrP Sc , vary in their susceptibility to SDS/peracetic acid effect on the N-terminus. Homogenates were prepared from brains of Syrian hamster inoculated with either Sc237, 139H, Me7H or DY prions and from brains of mice inoculated with either with RML, 139A, Me7, 87V, and 22A prion. When treated with SDS and peracetic acid for 30 min at room temperature all PrP Sc  strains were denatured as judged by western blotting using D18 after proteinase K. In order to visualize the residual PrP Sc  from treated homogenates, it was necessary to load 100 μg of protein per lane. From non-treated samples only 20 μg protein was loaded. The results show that treated Syrian hamster strains 139H and Me7H as well as mice strains Me7, 22A and 22V had a MW of 27-30 kDa—see  FIG. 10 . Syrian hamster Sc237  FIG. 10A , and mouse RML  FIG. 10B , as well as 139A had a MW of 22 kDa. The results indicate that the increase susceptibility of residues 90-112 to denaturation by peracetic SDS is dependent on the conformation of prion strain. Accordingly, the susceptibility can be used to differentiate between strains of PrP Sc . It is important to emphasis that the majority of PrP Sc  molecules are fully denatured regardless of the strain of species. The results also show in  FIG. 11  that treatment for 30 min at room temperature with peracetic acid and SDS denatures PrP Sc  of all tested prion strains including mouse 301V, bovine BSE, vCJD, sporadic CJD and different familial CJD cases. Similar treatment of scrapie sheep brain homogenate resulted in the elimination of all PrP Sc . The strong denaturation effect of peracetic acid combined with SDS does not at this time make it possible to determine the molecular weight of residual PrP Sc  from these prion strains.  
      Mechanism of Prion Disinfection  
      The combination of SDS and acetic acid denatures PrP Sc  and reduces prion infectivity in brain homogenates and prion-coated stainless steel wires. When used alone 3% Hydrogen peroxide does not reduce prion infectivity {Brown, P., R: G. Rohwer, et al. (1982). “Effect of chemicals, heat, and histopathologic processing on high-infectivity hamster-adapted scrapie virus.”  J. Infect. Dis.  145: 683-687}. It has also been shown that 2% peracetic acid will inactivate the infectivity in intact brain tissue {Taylor, D. M. (1991). “Resistance of the ME7 scrapie agent to peracetic acid.”  Vet Microbiol  27: 19-24.}. However, none of the concentrations of peracetic acid tested (19% up to 24 h) was effective in order to inactivate the infectivity of brain homogenates. The results provided here show that treatment of prion infected brain homogenates with a formulation of 0.2% peracetic acid and SDS denatures most of the PrP Sc  in brain homogenates. As peracetic acid is acetic acid plus oxygen the results show that oxidation synergies with SDS at low pH to denature PrP Sc . This is confirmed by other results showing that another oxidizing agent (hydrogen peroxide, H 2 O 2 ) in the presence of SDS and acetic acid is as robust as a denaturant as compared to peracetic acid combined with SDS. Results provided here shows that a solution of peracetic acid, H 2 O 2  and SDS is more robust than any combinations of two of these components.  
      Hydrogen peroxide and peracetic acid in the presence of metal ions lead to the production of highly toxic hydroxyl radical [Block, S. S. (2001). Peroxygen compounds.  Disinfection, Sterilization, and Preservation.  S. S. Block. Philadelphia, Lippincott Williams &amp; Wilkins: 185-204.]. The hydroxyl radical is said to be the strongest oxidant known. Hydroxyl radical, being highly reactive, can attack proteins, lipids, and DNA. Hydroxyl radicals can also oxidize Sulfhydryl groups and double bonds present in a protein. The presence of iron and copper in the brain promote the formation free radicals. This shows that denaturation of PrP Sc  by this formulation is mediated by the synergistic effect of SDS, low pH, and oxidation. The likely mechanism of action is a combination of the protonation of PrP Sc , by the low pH, altering its conformation in such a way as to expose the hydrophobic core of the protein to SDS mediated denaturation and attack by hydroxyl free radicals.  
      The results of the present invention also show that a combination of the cationic (positively charge) detergent Cetyltrimethylammonium bromide (CTAB), which belongs to a chemical group defined as Quaternary ammonium compounds and peracetic acid denatures PrP Sc . The mechanism of action of this detergent is unknown at this stage. The presence of bromide ions could catalyze the formation of reactive bromide hydroxyl radicals; reaction: OH+Br − →BrOH − .  
     Combination Treatment  
      The invention may be used in combination with traditional instrument sterilization methods. Those methods include the use of ethylene oxide gas (EtO) and steam as well as a method using low-temperature hydrogen peroxide gas plasma or a combination of both of these methods. The method may use a combination of hydrogen peroxide vapor and low-temperature gas plasma to rapidly sterilize medical instruments without leaving toxic residues. This technology may be carried out without the limitations or risks associated with peracetic acid, steam, and ethylene oxide gas (EtO) systems.  
      The present invention may be used in combination with a method that is particularly suited to heat-sensitive and moisture-sensitive instruments, which method includes 5 phases:  
      1. The Vacuum Phase  
      A chamber with instruments to be sterilized and with a formulation of the invention thereon is evacuated, reducing internal pressure in preparation for the subsequent reaction. Because the next step uses hydrogen peroxide the formulation of the invention may be comprised only of SDS, or SDS and an acid component such as acetic acid.  
      2. The Injection Phase  
      A measured amount of liquid peroxide is injected into the chamber, evaporating the aqueous hydrogen peroxide solution and dispersing it into the chamber, where it contacts proteins (e.g. prions) and any microorganism (bacteria, virus or fungus) on any surface of the instruments.  
      3. The Diffusion Phase  
      The hydrogen peroxide vapor permeates the chamber, exposing all load surfaces to the sterilant and rapidly sterilizes devices and materials without leaving any toxic residues. At the completion of this phase, the chamber pressure is reduced and the plasma discharge is initiated.  
      4. The Plasma Phase  
      An electromagnetic field is created in which the hydrogen peroxide vapor breaks apart, producing a low-temperature plasma cloud that contains ultraviolet light and free radicals. Following the reaction, the activated components lose their high energy and recombine to form oxygen and water.  
      Phases 1, 2, and 3 may be run a second time or a plurality of times for added efficacy. This built-in reprocessing assures optimal sterilization for even the most difficult-to-sterilize devices.  
      5. The Vent Phase  
      The chamber is vented with filtered air to equalize the pressure enabling the chamber door to be opened. There is no need for aeration or cool-down. Devices are ready for immediate use.  
                              FORMULATION 1                             Component   wt %                       Water   10-98           Acid    1-20           Detergent    1-20           Hydrogen peroxide   0.01-5                        
 
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 2 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
               
                   
                 Water 
                 10-98 
               
               
                   
                 Acetic acid 
                  1-20 
               
               
                   
                 Linear alkyl Sulfonate 
                  1-20 
               
               
                   
                 Hydrogen peroxide 
                 0.01-5   
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 3 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
               
                   
                 Water and Hydrogen 
                 10-99 
               
               
                   
                 peroxide 
               
               
                   
                 Acetic acid 
                  1-20 
               
               
                   
                 SDS 
                 0.01-10   
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 4 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
               
                   
                 Water 
                 1-98 
               
               
                   
                 Alcohol 
                 0-98 
               
               
                   
                 Acid 
                 1-20 
               
               
                   
                 Detergent 
                 1-20 
               
               
                   
                 Hydrogen peroxide 
                 0.1-5   
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 5 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
               
                   
                 Water 
                 1-99 
               
               
                   
                 Acid 
                 1-20 
               
               
                   
                 Hydrogen peroxide 
                 0.1-5   
               
               
                   
                 CTAB 
                 1-20 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 6 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
               
                   
                 Water 
                    3-98.889 
               
               
                   
                 Antimicrobial active Agent 
                 0.001-5    
               
               
                   
                 Acetic acid 
                 1-80 
               
               
                   
                 CTAB 
                 0.1-12   
               
               
                   
                 Hydrogen peroxide 
                 0.01-5    
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 7 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
            
           
           
               
               
               
            
               
                   
                 Hydrogen peroxide 
                 0.5 
               
               
                   
                 Ethanol 
                 74.0 
               
               
                   
                 SDS 
                 0.02 
               
               
                   
                 Acetic acid 
                 10.0 
               
               
                   
                 Purified water 
                 13.3 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 8 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
               
                   
                 Water 
                    3-98.889 
               
               
                   
                 SDS 
                 1-80 
               
               
                   
                 Acetic acid 
                 0.1-12   
               
               
                   
                 Hydrogen peroxide 
                 0.01-5    
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 9 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
               
                   
                 Sodium Acetate pH 
                 10% 
               
               
                   
                 4.0 ± 1 
               
               
                   
                 SDS 
                  4% 
               
               
                   
                 Water and hydrogen 
                 86% 
               
               
                   
                 peroxide 
               
               
                   
                   
               
            
           
         
       
     
     
       
         
           
               
            
               
                   
               
               
                   
               
               
                 FORMULATION 10 
               
            
           
           
               
               
               
            
               
                   
                 Component 
                 wt % 
               
               
                   
                   
               
               
                   
                 SDS 
                 4% 
               
               
                   
                 Peracetic acid 
                 0.1-10%  
               
               
                   
                 Water 
                   86-95.9% 
               
               
                   
                 Hydrogen peroxide 
                 6% 
               
               
                   
                   
               
            
           
         
       
     
     EXAMPLES  
      The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how to make and use the present invention, and are not intended to limit the scope of what the inventors regard as their invention nor are they intended to represent that the experiments below are all or the only experiments performed. Efforts have been made to ensure accuracy with respect to numbers used (e.g. amounts, temperature, etc.) but some experimental errors and deviations should be accounted for. Unless indicated otherwise, parts are parts by weight, molecular weight is weight average molecular weight, temperature is in degrees Centigrade, and pressure is at or near atmospheric.  
     Example 1  
     Effect of SDS, Acidic pH, and Temperature on Prion Infectivity  
      Samples of 1% Sc237-infected SHa brain homogenate containing 10 7  ID 50  units prion infectivity/ml were incubated with continuous shaking for 2 h in the specified buffer at the indicated temperature. Following incubation, samples were diluted 1:10 into PBS without calcium or magnesium plus 5 mg/ml BSA, and 50 μl aliquots were inoculated into 8 separate Syrian hamsters. The results are plotted in  FIG. 1  where the filled triangles are data for 1% NP40; 50 mM Tris Acetate, pH 7.0 at 37° C.; the filled circles are data for 1% NP40; 0.5% acetic acid, pH 3.6 at 37° C.; the open triangles are data for 1% SDS; 50 mM Tris Acetate, pH 7.0 at 37° C.; the closed squares are data for 1% SDS; 0.5% acetic acid, pH 3.6 at 20° C.; and the open circles are data for 1% SDS; 0.5% acetic acid, pH 3.6 at 37° C.; (open squares) 1% SDS; 0.5% acetic acid, pH 3.6 at 65° C.  
     Example 2  
     Effect of Detergent and pH on Protease-Resistant PrP SC    
      Samples of 1% Sc237-infected SHa brain homogenate were incubated for 15 min at 37° C. with detergent at the range of pH values indicated. Fifty mM sodium acetate buffers were used to maintain pH values 3 to 6, and 50 mM Tris acetate buffers were used to maintain pH values 7 to 10. The final pH value of each sample denoted above each corresponding lane was measured directly with a calibrated pH electrode (Radiometer Copenhagen). Following incubation, all samples were neutralized by the addition of an equal volume of 4% Sarkosyl; 100 mM HEPES, pH 7.5; 200 mM NaCl and subjected to limited proteolysis with 20 μg/ml proteinase K for 1 h at 37° C. These results are shown in  FIG. 2A .  
      Samples of 1% Sc237-infected SHa brain homogenate were incubated for 15 min at 37° C. in 1% SDS plus (1) 50 mM Tris acetate, pH 7.0; (2) 0.5% acetic acid, pH 3.6; (3) 50 mM glycine, pH 3.7; or (4) 0.2% peracetic acid (Sigma-Aldrich), pH 3.4. Following incubations, all samples were neutralized and proteinase K digested as described above for  FIG. 2A . The results are shown in  FIG. 2B .  
      Samples of 2.5% Sc237-infected brain homogenate were incubated with 4% detergent with (+) or without (−) 1% acetic acid at room temperature for 30 min. Lane pair assignments are as follows: (1) SDS; (2) Cholic Acid; (3) Deoxycholic Acid; (4) Triton X100; (5) NP40; (6) Tween 20; (7) CTAB; (8) Zwittergen; (9) Chaps. All paired samples (lanes  1 - 9 ) were neutralized by the addition of eight volumes of 4% Sarkosyl; 100 mM HEPES, pH 7.5; 200 mM NaCl and were subjected to limited proteolysis with 20 μg/ml proteinase K for 1 h at 37° C. The results are shown in  FIG. 2C . For all of  FIGS. 1A, 2B  and  2 C the apparent molecular weights based on migration of protein standards are 30 and 27 kDa.  
     Example 3  
      Samples of 20% Sc237-infected brain homogenate (10 μl/200 μg) were incubated with (+) or without (−) the following reagents; 1) 4% SDS, 2) different concentrations of H 2 O 2 , 3) 1% acetic acid, and 4) 0.2% peracetic acid at room temperature for 30 min to a final volume of 40 μl. Samples (lanes  1 - 9  of  FIG. 3A ) were diluted with 280 μl of neutralization buffer to final concentration of 100 mM NaCl, 2% Sarkosyl and 200 mM HEPES pH 7.5 and were subjected to limited proteolysis with 4 μg proteinase K for 1 h at 37° C. Western blots were loaded with 24 μl/lane and the results are shown in  FIG. 3A .  
      280 μl were treated with 1.120 ml of methanol/chloroform and PrP Sc  was analyzed with ELISA as described previously [Peretz, D., R. A. Williamson, et al. (2002). “A change in the conformation of prions accompanies the emergence of a new prion strain.”  Neuron  34: 921-932 and Peretz, D., R. A. Williamson, et al. (2002).  Antibodies inhibit prion formation and abolish prion infectivity.  Transmissible Spongiform Encephalopathies: New Perspectives for Prion Therapeutics, Paris, France, Editions de Condé. and the results are shown in  FIG. 3B .  
      PrP Sc  in  FIGS. 3A and 3B  were detected with Fab D18.  
     Example 4  
      Samples of 10% Sc237-infected brain homogenate (20 μl/200 μg) were incubated with (+) or without (−) the following reagents; 1) 5% H 2 O 2 , 2) 0.2% peracetic acid, 3) 2% SDS, and 4) 1% acetic acid, at room temperature for 30 min to final volume of 40 μl. Samples (lanes  1 - 10 ) were diluted with 280 μl of neutralization buffer to final concentration of 100 mM NaCl, 2% Sarkosyl and 200 mM HEPES pH 7.5 and were subjected to limited proteolysis with 4 μg proteinase K for 1 h at 37° C. Western blots were loaded with 100 μl/lane and PrP Sc  was detected with Fab D18. Blot was exposed to detection films for 15 seconds as shown in  FIG. 4A  and thereafter for 10 min. as shown in  FIG. 4B .  
     Example 5  
      10 μl samples of 20% Sc237-infected brain homogenate were incubated with: A) 2% detergent, B) 2% detergent, 5% H 2 O 2 , C) 2% detergent, 5% H 2 O 2 , 1% acetic acid and D) 2% detergent, 1% acetic acid. Controls homogenates were treated with: 1) PBS, 2) 1% acetic acid, 3) 5% H 2 O 2 , and 4) 1% acetic acid and 5% H 2 O 2 . Samples were diluted and PrP Sc  was detected with Western blotting using D18 recFab as described in Example 4 above and the results are shown in  FIG. 5 .  
     Example 6  
      10 μl samples of 20% Sc237-infected brain homogenate were incubated with 2% detergent with (+) or without (−) 1% peracetic acid at room temperature for 30 min. Lane pair assignments are as follows: (1) SDS; (2) Cholic Acid; (3) Deoxycholic Acid; (4) Triton X100; (5) NP40; (6) Tween 20; (7) CTAB; (8) Zwittergen; (9) Chaps. All paired samples (lanes  1 - 9 ) were neutralized with 280 μl of neutralization buffer to final concentration of 2% Sarkosyl; 200 mM HEPES, pH 7.5; 100 mM NaCl and were subjected to limited proteolysis with 4 μg proteinase K for 1 h at 37° C. The results are shown in  FIG. 6A  in which the Western blots were loaded with 24 μl/lane. For  FIG. 6B  280 μl were treated with 1.120 ml of methanol/chloroform and PrP Sc  was analyzed with ELISA as described previously [Peretz, 2002 #5885].  
      PrP Sc  in  FIGS. 6A and 6B  were detected with recFab D18.  
     Example 7  
      Samples of 10% Sc237-infected brain homogenate (20 μl/200 μg) were incubated with (+) or without (−) the following reagents; 1) 5% H 2 O 2 , 2) 0.2% peracetic acid, 3) 2% CTAB, and 4) 1% acetic acid, at room temperature for 30 min to final volume of 40 μl. Samples were diluted with 280 μl of neutralization buffer to final concentration of 100 mM NaCl, 2% Sarkosyl and 200 mM HEPES pH 7.5 and were subjected to limited proteolysis with 4 μg proteinase K for 1 h at 37° C. For  FIG. 7  Western blots were loaded with 100 μl/lane and PrP Sc  was detected with Fab D18  
     Example 8  
      10 μl samples of 20 % Sc237-infected brain homogenate were incubated with (+) or without (−) the following reagents: 1) 4% SDS, 2) increasing concentrations of peracetic acid, and 3) 1% acetic acid. Samples were diluted with 280 μl of neutralization buffer to final concentration of 100 mM NaCl, 2% Sarkosyl and 200 mM HEPES pH 7.5 and were subjected to limited proteolysis with 4 μg proteinase K for 1 h at 37° C. For  FIG. 8  Western blots were loaded with 24 μl/lane and PrP Sc  was detected with recFab D18.  
     Example 9  
      10 μl samples of 20% Sc237-infected brain homogenate were incubated with (+) or without (−) the following reagents: 1) proteinase K, 2) 4% SDS, and 3) different concentrations of PA. Samples were diluted with 280 μl of neutralization buffer to final concentration of 100 mM NaCl, 2% Sarkosyl and 200 mM HEPES pH 7.5 and were subjected to limited proteolysis with 4 μg proteinase K for 1 h at 37° C. For  FIGS. 9A and 9B  Western blots were loaded with 24 μl/lane and PrP Sc  was detected with recFab D18 for  FIG. 9A  and with mAb3F4 for  FIG. 9B .  
     Example 10  
      Brain homogenates were prepared from brains of Syrian hamster inoculated in  FIG. 10A  results with one of Sc237, 139H, Me7H or DY prions and for  FIG. 10B  the brains of mice inoculated with one of RML, 139A, Me7, 87V, or 22A prion. 10 μl samples of 20% prion-infected brain homogenate were incubated with; (A) 2% Sarkosyl or with (B) 4% SDS and 0.2% PA for 30 min at RT. Samples were diluted with 280 μl of neutralization buffer to final concentration of 100 mM NaCl, 2% Sarkosyl and 200 mM HEPES pH 7.5 and were subjected to limited proteolysis with 4 μg proteinase K for 1 h at 37° C. Western blots were loaded with 24 μl/lane and PrP Sc  was detected with recFab D18.  
     Example 11  
      Brain homogenates were prepared from brains of 1) Syrian hamster inoculated with Sc237 prions, 2) mouse inoculated 301V prions, 3) Bovine Spongiform Encephalopathy (BSE), 4) variant CJD patient, 5) sporadic CJD patient, M128M, 6) human fatal familial insomnia (FFI) patient D178N, 7) familial CJD patient E200K, M128M, and 8) familial CJD patient E200K, M128V. Samples of 10% brain homogenates were treated with; (A and B) none, (C) 4% SDS and 0.2% peracetic for 30 min at RT. Samples were diluted with 280 μl of neutralization buffer to final concentration of 100 mM NaCl, 2% Sarkosyl and 200 mM HEPES pH 7.5 and samples B and C were subjected to limited proteolysis with 4 μg (20 μg/ml) proteinase K for 1 h at 37° C. Western blots were loaded with various amounts of brain homogenate and were detected with mAb 6H4.  
      The preceding merely illustrates the principles of the invention. It will be appreciated that those skilled in the art will be able to devise various arrangements which, although not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Furthermore, all examples and conditional language recited herein are principally intended to aid the reader in understanding the principles of the invention and the concepts contributed by the inventors to furthering the art, and are to be construed as being without limitation to such specifically recited examples and conditions. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention as well as specific examples thereof, are intended to encompass both structural and functional equivalents thereof. Additionally, it is intended that such equivalents include both currently known equivalents and equivalents developed in the future, i.e., any elements developed that perform the same function, regardless of structure. The scope of the present invention, therefore, is not intended to be limited to the exemplary embodiments shown and described herein. Rather, the scope and spirit of present invention is embodied by the appended claims.