Donor screening for parvovirus B19 antibodies:

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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
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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.

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• Vireamic donations - antibody profiles
• 70 Vireamic (gt10e6 IU / ml) samples collected
  over 12- 18 month period
• Biotrin examined the B19 IgG and IgM levels

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• Specificity of the assay
• To evaluate integrity of positive results at the
  low end of the range - lt2.5 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

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Specificity of the assay
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• Effectiveness of IgG donor screening
• Normal donor population (Netherlands) 80 are IgG
  reactive
• Of all vireamic specimens detected by plasma PCR
  screen process (gt10e6 IU ml), in a 12-18 month
  period, 0 true IgG positives (n70)
• 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
• (gt10e5 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 gt 1 in 560,000)

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• 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

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• 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
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Servant et al, 2002
Test 500 donors from G1 (B19) region (UK) Test
500 donors from G3 (V9) region (Ghana)
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138 UK Donors tested (to date) using several
capsid antigens
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• 500 Ghanaian Donors
• gt 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 lt 5 yrs demonstrated
  that G3 Antisera reacts with Biotrins G1 antigen
  as well as with experimental G3 antigen.
• G3 derived antibodies are detected as well as G1
  derived antibodies using the current assay.

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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

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Sanquin Theo Cuypers Harry Bos Marco
Koppelman Cambridge JP Allain Daniel
Candotti Armen Parsyan Biotrin Shane
Kerr Amanda Corcoran