Porcine deltacoronavirus (PDCoV) is a globally distributed swine enteropathogenic virus that emerged in the last decade. A recent report of PDCoV infection in Haitian children also highlights potential public health implications. In this study, two monoclonal antibodies (mAbs), 1C2 and 5H5, were generated and showed high specificity for the PDCoV S protein. Both mAbs displayed high-titer neutralizing capabilities, suggesting their potential for passive immunotherapy. Epitope mapping revealed that the mAbs likely recognized conformational epitopes in the S1 subunit domains A and B of the native S protein, thereby blocking the interaction between the S1 receptor-binding domain and the cellular receptor, which could inhibit viral entry into host cells. This study offers new biological tools for PDCoV detection and lays the groundwork for the future development of porcine-specific antibodies for the prevention and treatment of PDCoV in piglets.

Encephalomyocarditis virus (EMCV), a potential zoonotic pathogen, poses significant socioeconomic and public health challenges across various host species. Although EMCV rarely triggers severe clinical symptoms in humans, its widespread prevalence and unique biological characteristics underscore the need for continuous surveillance and the development of effective therapeutics and prophylactics. In this study, we evaluated the neutralizing effects of a monoclonal antibody derived from the spleens of mice immunized with EMCV virus-like particles (VLPs), both in vitro and in vivo. Using recombinant DNA technology, we engineered a baculovirus system to express EMCVs P12A and 3C, facilitating the production of VLPs in Sf9 cells. These VLPs serve as antigens to immunize mice, leading to the isolation of the monoclonal antibody 45G3. This antibody exhibited high specificity for EMCV conformational epitopes, excluding linear epitopes, and demonstrated potent in vitro neutralizing activity, with an IC50 of 0.01873 μg/mL. Immunoelectron microscopy (IEM) revealed a strong direct interaction between the 45G3 antibody and EMCV particles. Virus adsorption inhibition assays demonstrated that 45G3 effectively blocked viral attachment, thereby preventing further infection of host cells. These findings further support the notion of a robust interaction between the virus and the antibody. Moreover, in vivo assessments revealed that 45G3 significantly reduced viral loads in treated mice and improved survival outcomes following EMCV exposure. Additionally, posttreatment analysis revealed reduced tissue damage and a markedly decreased inflammatory response in the brain, indicating that the 45G3 antibody effectively blocked viral infection, thereby mitigating tissue damage and enhancing survival. These findings position 45G3 as a promising candidate for EMCV management and provide a strong foundation for the future development of antiviral drugs targeting this widespread virus.