Study Purpose: The emergence of Chikunungya virus (ChikV) infection in the western hemisphere has raised concerns of donor-derived transmission. We assessed the prevalence of recent ChikV infection among deceased donors from OPTN/UNOS Region 5 by measuring ChikV IgM in serum/plasma using 2 EIA kits.

Methods: Samples from 300 organ and 700 tissue donors collected November 2014 – March 2015 were de-identified and tested for ChikV IgM using 2 EIAs. The Euroimmun kit is an indirect EIA utilizing sample diluent containing anti-human IgG, ChikV antigen-coated wells, and anti-human IgM conjugate. The InBios kit is an IgM-capture EIA utilizing anti-human IgM coated wells, soluble ChikV antigens, and anti-ChikV conjugate; samples positive (Pos) in the InBios EIA were retested with background subtraction to identify false-Pos reactivity. Samples with a final Equivocal (Eq) or Pos result in either assay were tested for ChikV IgG and IgM at Focus Diagnostics using indirect immunofluorescence assays (IFA). One sample Pos in the InBios EIA but negative (Neg) in the Euroimmun EIA was sent to the California Dept. of Public Health (CDPH) for evaluation.

Results:

#no Eq zone for this assay ^performed only on InBios screen Pos samples *At CDPH, sample also CHikV IgM-Neg IgG-Pos by IFA, and ChikV antibody Pos by PRNT

All 38 samples Eq/Pos in the Euroimmun EIA were Neg for IgM and IgG by IFA. Of 26 samples Pos in the InBios screening EIA, 1 was still Pos when retested with background subtraction, and IgM-Neg but IgG-Pos by IFA at both Focus and CDPH; in plaque reduction neutralization testing (PRNT) at CDPH, this sample neutralized ChikV but not western equine encephalitis virus.

Conclusions: IgG and PRNT findings for the 1 sample Pos in the InBios ChikV IgM EIA after background subtraction are consistent with this result representing a true Pos, thus indicating increased sensitivity of this EIA over IFA. A ChikV IgM prevalence rate of 1:1000 indicates that recent ChikV infection is more common than expected among OPTN/UNOS Region 5 donors, and underscores the need to monitor for recent ChikV infection among returnees from endemic areas. Any screening assay employed should be optimized to avoid false-Pos results.

CITATION INFORMATION: Prince H, Altrich M, Nowicki M. Assessment of Chikungunya IgM Prevalence Among Deceased Organ and Tissue Donors Using Two Enzyme Immunoassay (EIA) Kits. Am J Transplant. 2016;16 (suppl 3).

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