Citations

The taxonomic position of Yersinia kristensenii subsp. rochesterensis and Yersinia occitanica was re-evaluated by genomic analysis. Average nucleotide identity (ANI), digital DNA–DNA hybridization values, and phylogenetic analyses of the type strains indicate that Y. kristensenii subsp. rochesterensis and Y. occitanica are the same genospecies. Additionally, the overall genomic relatedness index (OGRI) values reveal that Y. kristensenii subsp. rochesterensis should be elevated to species status as Yersinia rochesterensis sp. nov.

Direct detection of Zika virus (ZIKV) nucleic acid with nucleic acid tests is definitive laboratory evidence of infection. Initial studies suggest that the ZIKV viremic period is limited, leading the Centers for Disease Control and Prevention to recommend that nucleic acid tests be utilized only up to 14 days postsymptom onset in serum and urine. The host immune response to flaviviruses, including to ZIKV, primarily targets the viral envelope (E) protein, which has three main domains (ED I–III). Recent studies suggest that neutralizing antibodies against the EDIII domain are relatively specific and potentially able to discriminate between ZIKV and dengue virus, which share 29% amino acid homology at that region. Comparatively, neutralizing antibodies to EDI and EDII, with amino acid homologies of 35 and 51% between these two viruses, respectively, are highly cross-reactive and likely responsible for the nonspecific reactions observed in the respective serologic assays. The current article describes the humoral immune response to ZIKV, reviews serologic assays for detection of antibodies to ZIKV, discusses performance characteristics of commercially available tests, and summarizes the strengths and limitations of currently available serologic methods. Assays examined in the review include the Centers for Disease Control and Prevention Zika IgM antibody capture ELISA, InBios ZIKV Detect IgM Capture ELISA, DiaSorin, LIAISON XL Zika Capture IgM Assay, Euroimmun anti-ZIKV IgM ELISA, and plaque reduction neutralization tests. Despite the availability of multiple diagnostic tests, there remains a need for modified and novel testing strategies, including the potential use of multiple enzyme immunoassays either in parallel or sequentially and IgG in addition to IgM determination.

ABSTRACT Serologic evaluation for Zika virus (ZIKV) infection currently includes an initial screen using an anti-ZIKV IgM antibody capture enzyme-linked immunosorbent assay (MAC-ELISA) followed by supplemental testing of specimens with nonnegative results by a plaque reduction neutralization test (PRNT). We compared the performance characteristics of three ELISAs for the detection of IgM class antibodies to ZIKV, including the Centers for Disease Control and Prevention (CDC) Zika MAC-ELISA, the InBios ZIKV Detect MAC-ELISA, and the Euroimmun anti-Zika Virus IgM ELISA. Additionally, we present our initial experiences with ZIKV serologic testing from a national reference laboratory perspective. Using both retrospectively and prospectively collected specimens from patients with possible ZIKV infection, we show that the CDC and InBios MAC-ELISAs perform comparably to each other, with positive agreement, negative agreement, and interrater kappa values ranging from 87.5% to 93.1%, 95.7% to 98.5%, and 0.52 to 0.83, respectively. In contrast, comparison of the Euroimmun ZIKV ELISA to either the CDC or InBios MAC-ELISAs resulted in positive agreement, negative agreement, and interrater kappa values ranging from 17.9% to 42.9%, 91.7% to 98.6%, and 0.10 to 0.39, respectively. Among the 19 prospective samples submitted for PRNT, nine were negative, eight specimens had neutralizing antibodies to a flavivirus (unable to be identified), and one sample each was confirmed for ZIKV or dengue virus infection. This study highlights the ongoing challenges associated with serologic diagnosis of ZIKV infection. Although the availability of a commercial serologic test for ZIKV has greatly expanded the national capacity for such testing, the need to further characterize and improve these assays, particularly with regard to specificity, remains.