Porcine epidemic diarrhea virus (PEDV) is a highly contagious coronavirus that causes severe diarrhea and death in neonatal piglets. Passive immunization with neutralizing antibodies against PEDV is an effective prevention measure. In this study, single chain fragment variable (scFv) antibodies against PEDV were screened from the porcine scFv phage display library. After four rounds of biopanning, scFvs that showed higher affinity to the PEDV antigen were selected for further study. The scFv genes were cloned into the expression plasmid for recombinant protein expression. These scFvs were shown to inhibit PEDV infectivity by the plaque reduction neutralization assay. Immunofluorescence assay (IFA) revealed that the epitopes recognized by these scFvs were in the S1 region of the spike protein. The potential of scFvs to provide prevention against PEDV infections in piglets was further investigated. Piglets orally administered scFvs showed no to mild clinical symptoms, significantly less viral shedding, no mortality and no intestinal lesions. The field application also revealed that the survival rate of piglets was significantly increased by oral administration of scFvs. Our data support the potential role of scFvs in the prevention and treatment of PEDV infection.

The Omicron variant has swept through most countries and become a dominant circulating strain, replacing the Delta variant. The evolutionary history of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) suggests that the onset of another variant (possibly another variant of concern (VOC) is inevitable. Therefore, the development of therapeutics that enable treatments for all Omicron-included VOCs/variants of interest (VOIs) and future variants is desired. Recently, the recombinant receptor decoy therapeutic angiotensin-converting enzyme 2 (ACE2)-Fc has exhibited good safety in a phase 1 clinical trial; therefore, its variant-resistant profile needs to be understood. Here, we conducted a comprehensive evaluation of its neutralization breadth against the Omicron variant and other VOCs/VOIs. Furthermore, to evaluate its resistance to future variants, we investigated its ability to neutralize various single-residue mutated variants. Next, we demonstrated its resistance to evasion via an experiment that rapidly and effectively stimulates virus evolution with a replication-competent virus model. In addition, we evaluated its efficacy for cocktail therapy. The combination of ACE2-Fc and neutralizing antibodies showed both efficacy and breadth in the simulation experiment. The underlying mechanism was revealed to be a synergistic effect in the cocktails. Collectively, this study deepens the understanding of the resistance profile of recombinant receptor decoy therapeutics and highlights the potential value of ACE2-Fc and neutralizing antibody cocktails in the subsequent anti-SARS-CoV-2 campaign. Furthermore, we also provide an effective method to study the resistance profile of antiviral agents and rapidly screen for potential cocktails to combat future variants.

Amyloidosis involves the deposition of misfolded proteins. Even though it is caused by different pathogenic mechanisms, in aggregate, it shares similar features. Here, we tested and confirmed a hypothesis that an amyloid antibody can be engineered by a few mutations to target a different species. Amyloid light chain (AL) and β-amyloid peptide (Aβ) are two therapeutic targets that are implicated in amyloid light chain amyloidosis and Alzheimer’s disease, respectively. Though crenezumab, an anti-Aβ antibody, is currently unsuccessful, we chose it as a model to computationally design and prepare crenezumab variants, aiming to discover a novel antibody with high affinity to AL fibrils and to establish a technology platform for repurposing amyloid monoclonal antibodies. We successfully re-engineered crenezumab to bind both Aβ42 oligomers and AL fibrils with high binding affinities. It is capable of reversing Aβ42-oligomers-induced cytotoxicity, decreasing the formation of AL fibrils, and alleviating AL-fibrils-induced cytotoxicity in vitro. Our research demonstrated that an amyloid antibody could be engineered by a few mutations to bind new amyloid sequences, providing an efficient way to reposition a therapeutic antibody to target different amyloid diseases.