Serological assays for emerging coronaviruses: Challenges and pitfalls

Abstract

More than a decade after the emergence of severe acute respiratory syndrome coronavirus (SARS-CoV) in 2002/2003 the occurrence of a novel CoV termed Middle East respiratory syndrome (MERS) CoV challenges researchers and public health authorities. To control spread and finally contain novel viruses, rapid identification and subsequent isolation of infected individuals and their contacts is of utmost importance. Next to methods for nucleic acid detection, validated serological assays are particularly important as the timeframe for antibody detection is less restricted. During the SARS-CoV epidemic a wide variety of serological diagnostic assays were established using multiple methods as well as different viral antigens. Even though the majority of the developed assays showed high sensitivity and specificity, numerous studies reported on cross-reactive antibodies to antigens from wide-spread common cold associated CoVs. In order to improve preparedness and responsiveness during future outbreaks of novel CoVs, information and problems regarding serological diagnosis that occurred during the SARS-CoV should be acknowledged. In this review we summarize the performance of different serological assays as well as the applicability of the two main applied antigens (spike and nucleocapsid protein) used during the SARS-CoV outbreak. We highlight challenges and potential pitfalls that occur when dealing with a novel emerging coronavirus like MERS-CoV. In addition we describe problems that might occur when animal sera are tested in serological assays for the identification of putative reservoirs. Finally, we give a recommendation for a serological testing scheme and outline necessary improvements that should be implemented for a better preparedness.

Low Seroprevalence of Severe Fever with Thrombocytopenia Syndrome Virus Antibodies in Individuals Living in an Endemic Area in Japan

“…However, it may yield false-positive results (e.g., 1-2% of the test samples), resulting in an erroneous interpretation of seroepidemiology. Therefore, a neutralization assay is required to confirm the presence of virusspecific antibodies in serum samples (22)(23)(24). Among the 1,646 sera examined, 18 (1.1%) tested positive in the IgG ELISA.…”

Transmission of MERS-Coronavirus in Household Contacts

“…11 This test was developed with the use of samples obtained from small groups of humans and camels in preliminary studies. 7,12 The dilution of human serum samples in this test was 1:100. Additional technical details are provided in Section 1 in the Supplementary Appendix, available with the full text of this article at NEJM.org.…”

Kinetics of Serologic Responses to MERS Coronavirus Infection in Humans, South Korea

“…Antibody to MERS-CoV was detected by using the plaque reduction neutralization test (PRNT) and MERS-CoV S1 IgG ELISA (EUROIMMUN, Lübeck, Germany) ( 4 , 5 ) (Technical Appendix). MERS-CoV EMC was used for the PRNT assay; a 50% PRNT endpoint (PRNT 50 ) was used because it was more sensitive than the 90% PRNT cutoff in detecting mild infections ( 6 ).…”