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U.S. Department of Health and Human Services

Vaccines, Blood & Biologics

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Medical Product Purity: Maintaining Biologics and Other FDA-regulated Products Free of the Infectious Agents of Transmissible Spongiform Encephalopathies (TSE Agents or Prions)

Principal Investigator: David M. Asher, MD
Office / Division / Lab: OBRR / DETTD / LBTSEA

General Overview

Infections with transmissible spongiform encephalopathy agents (TSE agents or prions) cause incurable fatal brain disease. FDA regulatory policies and product reviews reduce the chance of TSE agent contamination of products and accidental exposures. Our laboratory studies ways to detect and eliminate these infectious agents from medical products.

TSE agents have previously contaminated products regulated by FDA and other US government agencies; the affected products include foods, animal feeds, animal vaccines, transplanted human tissues (cornea and brain membrane), human-derived hormones, and neurosurgical instruments. In the United Kingdom (UK), TSE has contaminated products derived from donated human blood used for transfusion. These products include red blood cell concentrates that were not treated to remove white blood cells and a plasma protein called Factor VIII (antihemophilic factor), which is one of the molecules involved in blood clotting. In the UK, contaminated beef also caused fatal infections with the agent responsible for bovine spongiform encephalopathy (popularly called "mad cow" disease).

We are working to improve detection of TSE agents in various source materials used to manufacture FDA-regulated products and to develop ways to eliminate TSE agents from contaminated products. The methods we use include animal studies, in vitro studies (studies using isolated cells and extracts of tissues), and evaluation of improved methods to detect and eliminate TSE agents from both source materials (original biological materials used to make products) and finished products.

Scientific Overview

TSE agents are notoriously difficult to inactivate. They become exceptionally resistant to disinfection when contaminated tissues dry on surfaces, as commonly occurs with instruments and work surfaces used to manufacture biological products and other FDA-regulated products.

We have developed accessible and reproducible methods to evaluate the effects of commonly used cleaning, disinfection and sterilization methods on model TSE agents dried onto glass or steel surfaces. Our results have shown that a number of harsh methods for cleaning and disinfecting surfaces, especially combinations of pressurized steam and chemical treatments, such as lye and chlorine bleach, can remove very large amounts of TSE agents from surfaces. Nevertheless, those techniques are not fully reliable.

Although no tests have been validated as reliably detecting the small amounts of TSE agents that may occasionally contaminate source materials used to manufacture animal-derived and human-derived products, a number of candidate assays have been described in recent years. This project compares the performance characteristics of several recently described and older reliable tests, such as Western immunoblotting, for detecting TSE agents. To date, no test has proved sufficiently sensitive and specific to screen human or animal blood or tissues (other than brain tissues) for the presence of small amounts of TSE agent. As potentially improved tests are described, the project attempts to validate them.


Transfusion 2015 Feb;55(2):405-12
Blood reference materials from macaques infected with variant Creutzfeldt-Jakob disease agent.
McDowell KL, Nag N, Franco Z, Bu M, Piccardo P, Cervenak J, Deslys JP, Comoy E, Asher DM, Gregori L

J Virol 2014 Dec;88(23):13732-6
Development of dose-response models of Creutzfeldt-Jakob disease infection in nonhuman primates for assessing the risk of transfusion-transmitted variant Creutzfeldt-Jakob disease.
Huang Y, Gregori L, Anderson SA, Asher DM, Yang H

Transfusion 2014 Sep;54(9):2194-201
Risk assessment for transmission of variant Creutzfeldt-Jakob disease by transfusion of red blood cells in the United States.
Yang H, Gregori L, Asher DM, Epstein JS, Anderson SA

J Gen Virol 2014 Jul;95(Pt 7):1612-8
Complex proteinopathy with accumulations of prion protein, hyperphosphorylated tau,alpha-synuclein and ubiquitin in experimental BSE of monkeys.
Piccardo P, Cervenak J, Bu M, Miller L, Asher DM

Virology 2013 Dec;447(1-2):208-12
Coding potential of UL/b' from the initial source of rhesus cytomegalovirus Strain 68-1.
Gill RB, Jason Bowman J, Krogmann T, Wollenberg K, Asher DM, Cohen JI

PLoS One 2013 Oct 24;8(10):e78710
Red-backed vole brain promotes highly efficient in vitro amplification of abnormal prion protein from macaque and human brains infected with variant creutzfeldt-jakob disease agent.
Nemecek J, Nag N, Carlson CM, Schneider JR, Heisey DM, Johnson CJ, Asher DM, Gregori L

Vox Sang 2012 Oct;103(3):260-72
Prion reduction of red-blood-cells.
Coste J, Prowse C, Grabmer C, Schennach H, Santos Prado Scuracchio P, Wendel SN, Germain M, Delage G, Krusius T, Ekblom-Kullberg S, Tiberghien P, O'Riordan J, Murphy WG, Flesland O, Turner M, Williamson L, Gregori L, Epstein J, Asher D, Panzer S, Reesink HW

J Comp Pathol 2012 Jul;147(1):84-93
Squirrel monkeys (Saimiri sciureus) infected with the agent of bovine spongiform encephalopathy develop tau pathology.
Piccardo P, Cervenak J, Yakovleva O, Gregori L, Pomeroy K, Cook A, Muhammad FS, Seuberlich T, Cervenakova L, Asher DM

Emerg Infect Dis 2011 Dec;17(12):2262-9
Candidate cell substrates, vaccine production, and transmissible spongiform encephalopathies.
Piccardo P, Cervenakova L, Vasilyeva I, Yakovleva O, Bacik I, Cervenak J, McKenzie C, Kurillova L, Gregori L, Pomeroy K, Asher DM

Transfusion 2011 Aug;51(8):1855-71
FDA workshop on emerging infectious diseases: evaluating emerging infectious diseases (EIDs) for transfusion safety.
Atreya C, Nakhasi H, Mied P, Epstein J, Hughes J, Gwinn M, Kleinman S, Dodd R, Stramer S, Walderhaug M, Ganz P, Goodrich R, Tibbetts C, Asher D

Transfusion 2011 Aug;51(8):1755-68
Fukuoka-1 strain of transmissible spongiform encephalopathy agent infects murine bone marrow-derived cells with features of mesenchymal stem cells.
Cervenakova L, Akimov S, Vasilyeva I, Yakovleva O, McKenzie C, Cervenak J, Piccardo P, Asher DM

Infect Control Hosp Epidemiol 2010 Dec;31(12):1304-6
Disinfection and sterilization of prion-contaminated medical instruments.
Belay ED, Schonberger LB, Brown P, Priola SA, Chesebro B, Will RG, Asher DM

Transfusion 2009 Dec;49(12):2759-71
Transfusion-transmitted babesiosis in the United States: summary of a workshop.
Gubernot DM, Nakhasi HL, Mied PA, Asher DM, Epstein JS, Kumar S

Philos Trans R Soc Lond B Biol Sci 2008 Nov 27;363(1510):3618-25
Kuru: memories of the NIH years.
Asher DM

J Am Assoc Lab Anim Sci 2008 Jul;47(4):64-7
Visceral and neural larva migrans in rhesus macaques.
Gozalo AS, Maximova OA, StClaire MC, Montali RJ, Ward JM, Cheng LI, Elkins WR, Kazacos KR

J Virol 2008 Jun;82(11):5255-68
Comparative neuropathogenesis and neurovirulence of attenuated flaviviruses in nonhuman primates.
Maximova OA, Ward JM, Asher DM, St Claire M, Finneyfrock BW, Speicher JM, Murphy BR, Pletnev AG

J Histochem Cytochem 2006 Jan;54(1):97-107
Computerized Morphometric Analysis of Pathological Prion Protein Deposition in Scrapie-Infected Hamster Brain.
Maximova OA, Taffs RE, Pomeroy KL, Piccardo P, Asher DM

Curr Opin Biotechnol 2005 Oct;16(5):561-7
The clearance of viruses and transmissible spongiform encephalopathy agents from biologicals.
Farshid M, Taffs RE, Scott D, Asher DM, Brorson K

J Infect Dis 2005 Apr 1;191(7):1123-8
The rat-based neurovirulence safety test for the assessment of mumps virus neurovirulence in humans: an international collaborative study.
Rubin SA, Afzal MA, Powell CL, Bentley ML, Auda GR, Taffs RE, Carbone KM

J Gen Virol 2004 Jun;85(Pt 6):1777-1784
Standards for the assay of Creutzfeldt-Jakob disease specimens.
Minor P, Newham J, Jones N, Bergeron C, Gregori L, Asher D, Van Engelenburg F, Stroebel T, Vey M, Barnard G, Head M, The WHO Working Group on International Reference Materials for the Diagnosis and Study of Transmissible Spongiform Encephalopathies

AIDS Res Hum Retroviruses 2004 May;20(5):507-12
HIV Type 2 Primary Isolates Induce a Lower Degree of Apoptosis "in Vitro" Compared with HIV Type 1 Primary Isolates.
Machuca A, Ding L, Taffs R, Lee S, Wood O, Hu J, Hewlett I

Vaccine 2004 Mar 29;22(11-12):1486-93
Mouse neurotoxicity test for vaccinia-based smallpox vaccines.
Li Z, Rubin SA, Taffs RE, Merchlinsky M, Ye Z, Carbone KM



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