Anti-B19 screening for safe cellular blood products for at

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Anti-B19 screening for safe cellular blood
products for atrisk patients
Harry Bos on behalf of Project Group Parvo B19
Safe Blood Components (Theo Cuijpers, Marco
Koppelman, John Jongerius, Maarten Koot, et al.)

• SoGAT XVIII, USA, May 24-25th, 2005

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Parvovirus B19

• Small non enveloped virus 23 nm.
• Single-stranded DNA genome approx. 5500 nucl.
• Encoding 3 proteins
• VP1 5 of capsid
• VP2 95 of capsid
• NS1 non-structural for viral replication
• Erythrovirus
• Highly thropic for erythroid progenitor cells
• Infected cells undergo lysis caused by expression
  of NS1
• Decline in red blood cell count and haemoglobin

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Clinical manifestation of infection

• Epidemiology
• - Seroprevalence in adults world-wide approx.
  50-80
• - Seroconversion rate for adults is about 0.8
  per year
• Healthy individuals
• - Erythema infectiosum (fifth disease)
• - Chills
• - Headache
• - Rash
• - No clinical symptoms

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Risk groups for B19 infections

• Women during second trimester of pregnancy
• - Intra uterine fetal death (10)
• - Hydrops fetalis (3)
• Patients with congenital or acquired haemolytic
  anaemia
• Cellular immunodeficient patients
• - Aplastic crisis
• - Prolonged bone marrow damage and aplasia
• - Bone marrow transplantation

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Health Council of the Netherlands

• B19 may cause serious complications in risk
  groups
• B19 can be transmitted by blood tranfusion
• B19 infection in healthy individuals
• - Formation of protective Antibodies
• - Sometimes persistance of B19 virus for some
  time
• B19 safe blood components from
• - Donors with IgG Antibodies
• - Interval at least six months
• ) Council of the Netherlands Bloodproducts and
  Parvovirus B19. 2002 publication no. 2002/07

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Health Council of the Netherlands

• Plasma products
• The risk-group approach can not be used for
  plasma products
• because of their large-scale production and use.
• Approach for blood derivatives
• - Lowering the load in manufacturing pools by
  NAT screening and removal of high load units
  (gt5 x 106 IU/ml)

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Estimation of demand of Parvo safe blood products
in the Netherlands

• Erythrocyte concentrates 54,800 (8)
• Plasma 9,950 (8)
• Thrombocyte concentrates 11,000 (22) equivalent
  to
• 56,000 donor units
• ? Delivery of thrombocyte concentrates is the
  determing factor in the number of donors to be
  screened for B19
• ? Total numbers of donors to be screened 250,000
• 50 of the donorpopulation

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B19 IgG antibody screening

• Screening Assay
• - Biotrin Parvovirus B19 Sandwich ELISA
• - a-VP2 IgG
• - FDA cleared B19 ELISA
• Automation of the screening assay
• - Automatic pipetting device Tecan Genesis
• - ELISA back-end processor Ortho Summit Processor

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OD/CO for reactive a-Parvo B19 result 25,500
donations first time tested
Reactive OD/CO gt 1.0 80.1 Reactive OD/CO gt
1.5 78.7
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Status Anti-parvo B19 Testing April 1st, 2005
Reactive OD/CO gt 1.5 75.4 First time
tested Realised number 244,572 Reactive (OD/CO
gt 1.5) 184,468 Firist and second time
tested Reactive (OD/CO gt 1.5) 124,932 Desired
number first and second time reactives 125,000
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Status demand of Parvo safe cellular blood
products in the Netherlands, April 1th, 2005
Explicit demand of hospitals? Division
Northeast lt 10 Division Southeast 15 Division
Southwest 16 Division Northwest 10-20
thrombocyte concentrates weekly ?) The
Parvo status of the product is printed standard
on the label of the bloodproduct
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Limitations of the B19 screening method
A) False positive reactions - 1 donor
low pos OD/CO ratio

• Persistance of B19 virus in infected donors for a
  period of
• more than six months
• - 2 donors high pos OD/CO ratio, low B19
  DNA load
• Remark Blood products will probably not be
  infectious, because the high titer of B19
  antibodies will neutralise the virus present in
  a low concentration.

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Persistent B19 infection (B)
Donor 1
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Alternative Screening Based on Natural History of
Infection.

• Further RD on the testing system in place.
• Follow up of acute infected donors found in
  plasma-screening
• Sensitive B19 NAT of 5000 donations 6 month
  bleeding (2nd IgG anti-Parvo screening). False
  positive rate IgG test?
• Possible Consequences
• Extension of the 6 month-interval period to the
• length of the observed viremic period
• Parvo-NAT screening of donation for safe product
• IgM and IgG screening of donation for the safe
  product
• Or combination of these approaches

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Projects under consideration to improve the
screening method

• - Determine the false positive rates of the
  different brands of IgG anti-Parvo assays
• - Determine the in vitro neutralising effect of
  B19 antibodies (e.g. a-VP1, a-VP2, a-NS1), using
  cohort of follow up samples of acute infected
  individuals.

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Conclusions
Parvo B19 safe blood components can be derived
from donors with IgG Antibodies tested at an
interval of at least six months. Parvo B19 safe
cellular blood products can be in case of a
transfusion used for risk groups for B19
infection. This approach will reduce serious
complications due to transfusion related B19
infection. Further research is in consideration
to improve the screening method.