Journal
JOURNAL OF CLINICAL MICROBIOLOGY
Volume 59, Issue 7, Pages -Publisher
AMER SOC MICROBIOLOGY
DOI: 10.1128/JCM.00514-21
Keywords
SARS-CoV-2; cross-reactivity; malaria; serology
Categories
Funding
- Plan for AIDS Relief (PEPFAR) [U2GGH002108]
- Global Funds
- Malaria through NACA
- Nigerian Institute of Medical Research
- Centers for Disease Control and Prevention
- Bill and Melinda Gates Foundation
- National Institute for Health Research [RP-PG-0217-20009]
- National Institutes of Health Research (NIHR) [RP-PG-0217-20009] Funding Source: National Institutes of Health Research (NIHR)
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Accurate SARS-CoV-2 serological assays are crucial for COVID-19 surveillance, but cross-reactivity issues were found in areas with malaria endemicity. A simple urea wash can help alleviate this cross-reactivity problem.
Accurate SARS-CoV-2 serological assays are critical for COVID-19 serosurveillance. However, previous studies have indicated possible cross-reactivity of these assays, including in areas where malaria is endemic. We tested 213 well-characterized prepandemic samples from Nigeria using two SARS-CoV-2 serological assays, Abbott Architect IgG and Euroimmun NCP IgG assay, both targeting SARS-CoV-2 nucleo-capsid protein. To assess antibody binding strength, an avidity assay was performed on these samples and on plasma from SARS-CoV-2 PCR-positive persons. Thirteen (6.1%) of 212 samples run on the Abbott assay and 38 (17.8%) of 213 run on the Euroimmun assay were positive. Anti-Plasmodium IgG levels were significantly higher among false positives for both Abbott and Euroimmun; no association was found with active Plasmodium falciparum infection. An avidity assay using various concentrations of urea wash in the Euroimmun assay reduced loosely bound IgG: of 37 positive/borderline prepandemic samples, 46%, 86%, 89%, and 97% became negative using 2 M, 4 M, 5 M, and 8 M urea washes, respectively. The wash slightly reduced avidity of antibodies from SARS-CoV-2 patients within 28 days of PCR confirmation; thereafter, avidity increased for all urea concentrations except 8 M. This validation found moderate to substantial crossreactivity on two SARS-CoV-2 serological assays using samples from a setting where malaria is endemic. A simple urea wash appeared to alleviate issues of cross-reactivity.
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