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Donor screening for parvovirus B19 antibodies: Reducing or eliminating the risk of transmission

Learn about the effectiveness of IgG donor screening for reducing the risk of parvovirus B19 transmission, antigen-based ELISA testing, specificity of the assay, and the current approaches to donor screening and testing. Collaboration with experts like Prof. JP Allain and ongoing studies on genotype-specific detection are discussed.

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Donor screening for parvovirus B19 antibodies: Reducing or eliminating the risk of transmission

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  1. Donor screening for parvovirus B19 antibodies: Reducing or eliminating the risk of transmission SoGAT 2005 Gordon Elliott Biotrin 93 The Rise Mount Merrion Dublin Ireland SoGAT 2005

  2. TMB TMB VP2 IgG ELISA HRP OD450 Electron Micrograph of Biotrin VP2 Capsids CE Marked FDA Approved • Intact Viral particles are essential for 100% detection of B19. • VP1/2 antigens expressed in E.Coli do not form particles and give 10-20% false negative IgG results. SoGAT 2005

  3. TMB TMB CE Marked FDA Approved VP2 IgG ELISA HRP OD450 TMB HRP CE Marked FDA Approved IgM ELISA VP2 OD450 TMB Virus Antigen ELISA HRP Research assay OD450 SoGAT 2005

  4. Vireamic donations - antibody profiles: • 70 Vireamic (>10e6 IU / ml) samples collected over 12- 18 month period • Biotrin examined the B19 IgG and IgM levels SoGAT 2005

  5. SoGAT 2005

  6. Specificity of the assay: • To evaluate integrity of positive results at the low end of the range - <2.5 index • In a panel of 500 blood donors, 350 (70%) were IgG positive. • 18 samples (3.5%) were ‘very low pos’, index 1.1 to 2.5 • These 18 samples were tested by confirmatory competitive (VP2) assay SoGAT 2005

  7. Specificity of the assay: SoGAT 2005

  8. Effectiveness of IgG donor screening: • Normal donor population (Netherlands) 80% are IgG reactive • Of all vireamic specimens detected by plasma PCR screen process (>10e6 IU ml), in a 12-18 month period, 0% true IgG positives (n=70) • Rate of parvo IgG in normal donors is possibly at least 80 times rate in vireamic donors • Typically 1 in 10,000 fresh blood product units donated are vireamic • (>10e5 IU / ml) (greater in epidemic) • Consider that with a 1 time IgG screen at the time of donation, the rate of vireamic donations may be better than 1 in 800,000 • (Allowing for 1 false positive in this case, 1.43% are ‘apparent reactive’ • rate of vireamic donations would be of the order of > 1 in 560,000) SoGAT 2005

  9. Current Sanquin Approach: The two-time testing model is clearly successful in reducing, if not eliminating, high vireamic donations. • Main drawback is requirement for time gap in two-time testing • One time screening using combined tests maybe possible: • 1) IgG+ / IgM- donors (zero of 70 viraemics tested) • 2) IgG+ / Parvo Ag- donors • 3) IgG+ / PCR low donors • Studies ongoing SoGAT 2005

  10. Use of antigen in Parvovirus IgG ELISAs • The Biotrin assay is based on G1 (B19) VP2 Capsid: • Is VP1 and VP2 required for detection of all positives? • Does the Biotrin assay work for Genotype 2 (A6) and Genotype 3 (V9)? Collaboration with Prof. JP Allain, Cambridge Transfusion Medicine SoGAT 2005

  11. CAMBRIDGE BIOTRIN CODE 1 Genotype 1 (B19) VP2 Genotype 1 (B19) VP1/2 Genotype 3 (V9) VP2 Genotype 3 (V9) VP1/2 ‘CAM 1’ ‘CAM2’ ‘CAM3’ ‘CAM4’ CODE 2 Servant et al, 2002 Test 500 donors from G1 (B19) region (UK) Test 500 donors from G3 (V9) region (Ghana) SoGAT 2005

  12. 138 UK Donors tested (to date) using several capsid antigens SoGAT 2005

  13. 500 Ghanaian Donors: • > 100 tested to date • Different index value distribution compared to European populations • Lower Index Values overall • But no difference in results between antigens. • Testing of Ghanaian Children < 5 yrs demonstrated that G3 Antisera reacts with Biotrin’s G1 antigen as well as with experimental G3 antigen. • G3 derived antibodies are detected as well as G1 derived antibodies using the current assay. SoGAT 2005

  14. An Antigen-Capture EIA for the detection of Parvovirus B19 in human plasma. • The first EIA for B19 Virus Detection. • Employs a classic “sandwich” EIA format. • Sensitivity of approximately 5 x 107 IU / ml. • High specificity, no false-positive results in over 500 normal human plasmas tested. • Capability to detect virus in the presence of high levels of anti-B19 IgM and / or IgG. • Detection of variants e.g. V9 SoGAT 2005

  15. SoGAT 2005

  16. Sanquin: Theo Cuypers Harry Bos Marco Koppelman Cambridge: JP Allain Daniel Candotti Armen Parsyan Biotrin: Shane Kerr Amanda Corcoran SoGAT 2005

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