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Guidance for Industry: Nucleic Acid Testing (NAT) to Reduce the Possible Risk of Parvovirus B19 Transmission by Plasma-Derived Products

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Additional copies of this guidance are available from the Office of Communication, Outreach and Development (OCOD) (HFM-40), 1401 Rockville Pike, Suite 200N, Rockville, MD 20852-1448, or by calling 1-800-835-4709 or 301-827-1800, or from the Internet at http://www.fda.gov/BiologicsBloodVaccines/GuidanceComplianceRegulatoryInformation/ Guidances/default.htm.

For questions on the content of this guidance, contact OCOD at the phone numbers listed above.

U.S. Department of Health and Human Services
Food and Drug Administration
Center for Biologics Evaluation and Research
July 2009

Table of Contents

Guidance for Industry

Nucleic Acid Testing (NAT) to Reduce the Possible Risk of Parvovirus B19 Transmission by Plasma-Derived Products

This guidance represents the Food and Drug Administration’s (FDA’s) current thinking on this topic.  It does not create or confer any rights for or on any person and does not operate to bind FDA or the public.  You can use an alternative approach if the approach satisfies the requirements of the applicable statutes and regulations.  If you want to discuss an alternative approach, contact the appropriate FDA staff.  If you cannot identify the appropriate FDA staff, call the appropriate number listed on the title page of this guidance.



We, FDA, are issuing this guidance to provide you, manufacturers of plasma-derived products, with recommendations for performing nucleic acid testing (NAT) for human parvovirus B19 as an in-process test for Source Plasma and recovered plasma used in the further manufacturing of plasma-derived products.  Such testing will identify and help to prevent the use of plasma units containing high levels of parvovirus B19.  This guidance also recommends how to report to FDA implementation of parvovirus B19 NAT.

We recognize that in the current business practice for parvovirus B19 NAT in-process testing, several weeks can elapse between collection of the units of Source Plasma or recovered plasma and identification of B19 NAT-positive pools or units.  We encourage manufacturers of plasma-derived products to employ practices that will reduce the time between product collection and in-process testing to allow for the meaningful notification of blood and plasma collection establishments of positive test results within the dating period of any blood components intended for use in transfusion.

This guidance finalizes the draft guidance of the same title, dated July 2008.

FDA’s guidance documents, including this guidance, do not establish legally enforceable responsibilities.  Instead, guidances describe the FDA’s current thinking on a topic and should be viewed only as recommendations, unless specific regulatory or statutory requirements are cited.  The use of the word should in FDA’s guidances means that something is suggested or recommended, but not required.

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Human parvovirus B19 is a small, non-enveloped single stranded DNA virus.  Virus clearance studies, using non-human parvoviruses as models for parvovirus B19, have indicated that this virus is highly resistant to all commonly used inactivation methods, including heat and solvent/detergent (S/D) treatment, and is also difficult to remove by filtration because of its small size.  More recent studies have demonstrated that human parvovirus B19 may be more readily cleared than certain model animal parvoviruses (Refs. 1, 2, 3 and 4).  The parvovirus B19 can be transmitted by blood components and certain plasma derivatives, and may cause morbidity to susceptible recipients such as pregnant women (and their fetuses exposed in utero), persons with underlying hemolytic disorders, and immune compromised individuals (Refs. 5 and 6).  The disease transmission by transfusion of blood components is rare.  However, extremely high levels of parvovirus B19, up to 1012 IU/mL, in plasma of acutely infected but asymptomatic donors may present a greater risk in plasma derivatives due to pooling of large numbers of plasma units in the manufacture of these products.  The virus can be detected by NAT in plasma pools when there are high levels of parvovirus B19 DNA in viremic donations.  For example, the parvovirus B19 DNA can be detected in various plasma-derived products, particularly in coagulation factors (Refs. 7 and 8).  There have been a few reports of parvovirus B19 infection associated with the administration of coagulation factors (Refs. 9 and 10) and S/D Treated Pooled Plasma (Refs. 5 and 11).  Parvovirus B19 DNA is less frequently detected in albumin and immunoglobulin products and, when detected, the levels are usually low.  There are no confirmed reports that albumin and immunoglobulin products have transmitted parvovirus B19 infection.

We have held or participated in several meetings to discuss the potential risk of parvovirus B19 infection by plasma-derived products, and the strategy for reducing such risk.  The meetings included FDA-sponsored NAT workshops in 1999 and 2001 (Refs. 12 and 13), Blood Products Advisory Committee (BPAC) meetings in 1999 and 2002 (Refs. 14, 15, and 16), the National Heart, Lung, and Blood Institute-sponsored Parvovirus B19 workshop in 1999 (Ref. 5), and an ad hoc Public Health Service (PHS) panel in 2002 (discussed at the 2002 BPAC meeting (Ref. 16)).  In these meetings, it was recognized that viral inactivation/removal steps that are routinely used in the manufacturing process of plasma-derived products do not alone appear to be sufficient to completely clear the virus if high viral load is present in the starting material.  Therefore, in these meetings, a common recommendation for mitigating the risk of parvovirus B19 transmission by plasma derivatives has been to limit the virus load in the manufacturing plasma pool by testing the plasma donations for high titer parvovirus B19 DNA, using a minipool format.  This viral load reduction strategy combined with the ability of the manufacturing process to clear the residual virus could greatly reduce the risk of parvovirus B19 infection by plasma-derived products.

The recommended limit in this guidance for viral load of parvovirus B19 DNA in the manufacturing plasma pool (i.e., not to exceed 104 IU/mL) was primarily derived from studies that were conducted on the transmission of parvovirus B19 associated with S/D Treated Pooled Plasma (Refs. 5, 11, and 14).  In principle, testing in a minipool format to measure the viral load for parvovirus B19 DNA in a manufacturing plasma pool is acceptable in order to exclude only the high-titer plasma donations, thereby avoiding too great a loss of plasma for further manufacturing.  Furthermore, during the viremic period for parvovirus B19 infected donors, which can be very lengthy, low levels of parvovirus B19 coexist with parvovirus B19 antibodies (potentially complexing with and neutralizing the virus).  Therefore, it is undesirable to remove plasma units with low levels of B19 DNA, because it would diminish the parvovirus B19 antibody levels in plasma pools and in some of the resulting plasma-derived products (Refs. 17 and 18).

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    We recommend that you implement the following procedures to detect the presence of parvovirus B19 DNA:

    • For all plasma-derived products, you should perform parvovirus B19 NAT as an in-process test to ensure that the viral load of parvovirus B19 DNA in the manufacturing pools does not exceed 104 IU/mL.
    • Use parvovirus B19 NAT on minipool samples to screen plasma units intended for further manufacturing into plasma-derived products.  Primers and probes selected for parvovirus B19 NAT should detect all known genotypes of the virus (Ref. 19).
    • When identified, you should not use individual plasma units, intended for further manufacturing into plasma-derived products, when such units are found to have a titer of parvovirus B19 DNA that might result in plasma manufacturing pools exceeding a parvovirus B19 DNA titer of 104 IU/mL.

    You should assess validation data demonstrating the accuracy, sensitivity, specificity, reproducibility, and other performance characteristics of the parvovirus B19 NAT assay used for the detection of parvovirus B19 DNA in the Source Plasma and recovered plasma, and for demonstrating that the viral load of parvovirus B19 DNA in the manufacturing pool does not exceed 104 IU/mL.

    If the above recommendations are implemented, you must inform FDA, as required under 21 CFR 601.12(a).  You may submit these changes as a “Supplement-Changes Being Effected” supplement (CBE supplement), under 21 CFR 601.12(c)(5).

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      1. Mani, B., Gerber, M., Lieby P., Boschetti, N., Kempf, C., Ros, C. Molecular mechanism underlying B19 virus inactivation and comparison to other parvoviruses. Transfusion (2007); 47: 1765‐1774.
      2. Blumel J, Stuhler A, Dichtemuller H. Kinetics of inactivating human parvovirus B19 and porcine parvovirus by dry‐heat treatment. Transfusion (2008); 48:790‐791.
      3. Berting A, Modrof J, Unger U, Gessner M, Klotz A, Poesler G, Kreil TR. Inactivation of parvovirus B19 during STIM‐4 vapor heat treatment of three coagulation factor concentrates. Transfusion (2008); 48:1220‐1226
      4. Boschetti N, Niederhauser I, Kempf C, Stuhler A, Lower J, Blumel J. Different susceptibility of B19 virus and mice minute virus to low pH treatment. Transfusion (2004); 44: 1079-1086.
      5. Brown, K.E., Young N.S., Alving, B.M., Luiz, H., and Barbosa, L.H.  Parvovirus B19 implications for transfusion medicine.  Transfusion (2001); 41:130-135.
      6. Young, N.S., and Brown, K.E.  Parvovirus B19.  The New England Journal of Medicine (2004); 350:586-597.
      7. Saldanha, J., and Minor, P.  Detection of human parvovirus B19 DNA in plasma pools and blood products derived from these pools: implications for efficiency and consistency of removal of B19 DNA during manufacture.  British Journal of Haematology (1996); 93:714-719.
      8. Schmidt, I., Blumel, J., Seitz, H., Willkommen, H., and Lower, J.  Parvovirus B19 DNA in plasma pools and plasma derivatives.  Vox Sanguinis (2001); 81:228-235.
      9. Blumel, J., et al.  Parvovirus B19 transmission by heat-treated clotting factor concentrates.  Transfusion (2002); 42:1473-1481.
      10. Wu, C.G., et al. Parvovirus B19 transmission by a high-purity factor VIII concentrate.  Transfusion (2005); 45:1003-1010.
      11. Koenigbauer, U.F., Eastlund, T., and Day, J.W.  Clinical illness due to parvovirus B19 infection after infusion of solvent/detergent-treated pooled plasma.  Transfusion (2000); 40:1203-1206.
      12. Transcript of Workshop on Implementation of Nucleic Acid Testing, December 14, 1999. 
        http://www.fda.gov/downloads/BiologicsBloodVaccines/ NewsEvents/WorkshopsMeetingsConferences/TranscriptsMinutes/UCM055438.pdf.
      13. Transcript of Application of Nucleic Acid Testing To Blood Borne Pathogens and Emerging Technologies Workshop, December 4, 2001.
        http://www.fda.gov/downloads/BiologicsBloodVaccines/ NewsEvents/WorkshopsMeetingsConferences/TranscriptsMinutes/UCM055339.pdf.
      14. Transcript of FDA’s Blood Products Advisory Committee (BPAC) Meeting, September 1999.
        http://www.fda.gov/AdvisoryCommittees/CommitteesMeetingMaterials/ BloodVaccinesandOtherBiologics/BloodProductsAdvisoryCommittee/default.htm.
      15. Transcript of FDA’s Blood Products Advisory Committee (BPAC) Meeting, March 14, 2002.
        http://www.fda.gov/AdvisoryCommittees/CommitteesMeetingMaterials/ BloodVaccinesandOtherBiologics/BloodProductsAdvisoryCommittee/default.htm.
      16. Transcript of FDA’s Blood Products Advisory Committee (BPAC) Meeting, December 2002.
        http://www.fda.gov/AdvisoryCommittees/CommitteesMeetingMaterials/ BloodVaccinesandOtherBiologics/BloodProductsAdvisoryCommittee/default.htm.
      17. Lefrere, Jean-Jacques, et al. Persistent B19 infection in immunocompetent individuals: implications for transfusion safety.  Blood (2005); 106(8):2890-2895.
      18. Cassinotti, P., Siegl, G. Quantitative evidence for persistence of human parvovirus B19 DNA in an immunocompetent individual.  Eur J Clin Microbiol Infect Dis (2000); 19:886-895.
      19. Servant, A., et al. Genetic diversity within human erythroviruses: identification of three genotypes.  J Virol (2002); 76:9124-34.

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Contact FDA

(800) 835-4709
(301) 827-1800
Manufacturers Assistance and Technical Training Branch (CBER)

Division of Manufacturers Assistance and Training

Office of Communication, Outreach and Development

Food and Drug Administration

1401 Rockville Pike

Suite 200N/HFM-41

Rockville, MD 20852-1448