Improved Expression of SARS-CoV-2 Spike RBD Using the Insect Cell-Baculovirus System.

Insect cell-baculovirus expression vector system is one of the most established platforms to produce biological products, and it plays a fundamental role in the context of COVID-19 emergency, providing recombinant proteins for treatment, diagnosis, and prevention. SARS-CoV-2 infection is mediated by the interaction of the spike glycoprotein trimer via its receptor-binding domain (RBD) with the host's cellular receptor. As RBD is required for many applications, in the context of pandemic it is important to meet the challenge of producing a high amount of recombinant RBD (rRBD).

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.

Rapid and cost-effective process based on insect larvae for scale-up production of SARS-COV-2 spike protein for serological COVID-19 testing.

Serology testing for COVID-19 is important in evaluating active immune response against SARS-CoV-2, studying the antibody kinetics, and monitoring reinfections with genetic variants and new virus strains, in particular, the duration of antibodies in virus-exposed individuals and vaccine-mediated immunity. In this study, recombinant S protein of SARS-CoV-2 was expressed in Rachiplusia nu, an important agronomic plague. One gram of insect larvae produces an amount of S protein sufficient for 150 determinations in the ELISA method herein developed.