Rapid and Cost-Effective Diagnostic Blot Assays Based on the Use of Plant-Produced Recombinant Antigens: A Lesson Learned by SARS-CoV-2 RBD Antigen

The ongoing demand for reliable, cost-effective, and scalable diagnostic solutions during the SARS-CoV-2 pandemic has highlighted the need for innovative production platforms. Here, we present a plant-based molecular farming (PMF) strategy for the production of the receptor-binding domain (RBD) of the SARS-CoV-2 spike protein fused with Fc (RBDw-Fc). The RBDw-Fc antigen was transiently expressed in Nicotiana benthamiana plant, achieving high yields and purity. Antigen-antibody binding assays were used to assess its functionality. The purified antigen was used to develop a rapid diagnostic blot assay to screen both pre and post vaccinated and pre and post infected plasma EDTA samples with high sensitivity and specificity. Our results demonstrate that the RBDw-Fc-based assay is effective for SARS-CoV-2 detection, and offers significant advantages in terms of production speed, scalability, and cost-efficiency compared to traditional systems, such as cell-culture-based production. This kind of diagnostic test deliver accurate results in just few minutes, enhancing its applicability in clinical and resource-limited settings. This study highlights the versatility of PMF as a platform for producing high-quality reagents, with potential applications beyond SARS-CoV-2 diagnostics. The RBDw-Fc antigen-based method offers a model for the development of rapid, economical, and adaptable screening tools for emerging infectious diseases and future pandemics.