Receptor-binding domain–based immunoassays for serosurveillance differentiate efficiently between SARS-CoV2–exposed and non-exposed farmed mink

Abstract

During the COVID-19 pandemic, infection of farmed mink has become not only an economic issue but also a widespread public health concern. International agencies have advised the use of strict molecular and serosurveillance methods for monitoring the SARS-CoV2 status on mink farms. We developed 2 ELISAs and a duplex protein microarray immunoassay (MI), all in a double-recognition format (DR), to detect SARS-CoV2 antibodies specific to the receptor-binding domain (RBD) of the spike protein and to the full-length nucleoprotein (N) in mink sera. We collected 264 mink serum samples and 126 oropharyngeal samples from 5 Spanish mink farms. In both of the ELISAs and the MI, RBD performed better than N protein for serologic differentiation of mink from SARS-CoV2–positive and –negative farms. Therefore, RBD was the optimal antigenic target for serosurveillance of mink farms.

The Luciferase Immunoprecipitation System (LIPS) Targeting the Spike Protein of SARS-CoV-2 Is More Accurate than Nucleoprotein-Based LIPS and ELISAs for Mink Serology

“…In contrast, a recent study in humans showed that LIPS using antibodies against the N protein is more sensitive than the detection of antibodies against the S protein and that N antibodies generally appear earlier than spike antibodies [23]. Sera analysed in [23] derived from patients with positive PCR results only indicated an early stage of infection, whereas samples from animals analysed by other authors and the ones included in this study were derived from a later stage of infection [ 13,18,27]. Diferent results obtained in [23] on humans compared to published data on animals might be due to diferent sera origins or that anti-N antibodies appear earlier but also decrease faster than anti-S antibodies.…”

“…S protein mediates attachment to host cells and virion entry and contains the receptor-binding domain (RBD) [12]. Te full N and S proteins and diferent S domains, including RBD, have been used as antigens for testing the SARS-CoV-2 humoral immune response [13]. In a previous report, we evaluated the use of LIPS assays targeting the S and N protein (LIPS-S and LIPS-N) on fve diferent animal species, including mink [7].…”