Development of a competition ELISA (cELISA) for specific detection of Zika virus antibodies in human sera

Abstract

Abstract Infections by Zika virus (ZIKV), a member of the Flavivirus genus, can be diagnosed by virus isolation, detection of virus RNA or by serological methods for detecting ZIKV immunoglobulin M antibodies (IgM), a marker of recent infections, and immunoglobulin G antibodies (IgG), a marker of past infections. In some cases, where IgM antibodies may last for longer periods, accurate diagnosis of recent infections is not always possible. Because commercial and non-commercial serological tests are often confounded by cross-reactivity with other Flaviviruses there is a need for simple, ZIKV-specific serological tests. Here, we present the development of a ZIKV-specific ELISA in which cross-reacting antibodies in serum samples are competed and blocked by Dengue virus antigens (DENV). The competed sera are then tested by ELISA on ZIKV and DENV coated wells to enable a calculation of a ZIKV/DENV (Z/D) cutoff ratio. For the development and validation of the ZIKV specific cELISA we have used three groups of sera from Colombia. 49 sera were obtained in 2018 from individuals that have been infected with ZIKV during a 2016 outbreak. The outbreak was in a DENV endemic area. Another group of 19 sera were obtained from a known DENV endemic area with no evidence of any ZIKV infections. The third group of 12 sera were obtained from patients from an area with no known Flavivirus infections and therefore considered as negative for both ZIKV and DENV. A Z/D ratio of 1.5 was determined as the cutoff value for the specific determination of ZIKV positive or negative sera. Our analysis indicated a 85% agreement with the BOB assay, and a 78% agreement with the commercial IgG ELISA test. The estimated specificity and sensitivity for the cELISA were 70% and 82%, respectively.