Novel bridge multi-species ELISA for detection of SARS-CoV-2 antibodies.

Unlabelled: Considering the course of the current SARS-CoV-2 pandemic, it is important to have serological tests for monitoring humoral immune response against SARS-CoV-2 infection and vaccination. Herein we describe a novel bridge enzyme-linked immunosorbent assay (b-ELISA) for SARS-CoV-2 antibodies detection in human and other species, employing recombinant Spike protein as a unique antigen, which is produced at high scale in insect larvae.

Methods: Eighty two human control sera/plasmas and 169 COVID-19 patients' sera/plasmas, confirmed by rRT-PCR, were analyzed by the b-ELISA assay. In addition, a total of 27 animal sera (5 horses, 13 rats, 2 cats and 7 dogs) were employed in order to evaluate the b-ELISA in other animal species.

Results: Out of the 169 patient samples, 129 were positive for IgG anti-SARS-CoV-2 and 40 were negative when they were tested by ELISA COVIDAR® IgG. When a cut-off value of 5.0 SDs was established, 124 out of the 129 COVID-19 positive samples were also positive by our developed b-ELISA (sensitivity: 96.12%). Moreover, the test was able to evaluate the humoral immune response in animal models and also detected as positive a naturally infected cat and two dogs with symptoms, whose owners had suffered the COVID-19 disease.

Conclusion: The obtained results demonstrate that the method developed herein is versatile, as it is able to detect antibodies against SARS-CoV-2 in different animal species without the need to perform and optimize a new assay for each species.