Yanan Wu

Introduction: Porcine epidemic diarrhea virus (PEDV) is a highly contagious enteric pathogen that causes severe diarrhea and high mortality in neonatal piglets, leading to substantial economic losses in the swine industry. The nucleocapsid (N) protein is highly conserved and abundantly expressed during infection, making it a suitable target for serological detection. Methods: In this study, twomonoclonal antibodies (mAbs), C9 and G11, directed against the PEDV N protein were used to define minimal linear epitopes. A stepwise truncation approach based on overlapping recombinant fragments was applied to localize the antigenic regions. Results: The results showed that mAb C9 and mAb G11 recognized the minimal epitopes ⁵⁸ RWRM ⁶¹ and ¹⁵ PLSL ¹⁸ , respectively. Sequence analysis indicated that both epitopes are highly conserved among representative PEDV strains from different genotypes. In addition, structural modeling suggested that these regions are exposed on the surface of the N protein, consistent with their accessibility to antibody binding. Discussion: These findings provide a more precise characterization of antigenic sites within the PEDVNprotein andmay be useful for the development of specific and reliable serological assays.

Porcine reproductive and respiratory syndrome (PRRS) is an immunosuppressive disease caused by PRRS virus (PRRSV). PRRSV infection not only compromises the host immune defenses, but also predisposes the host to secondary infections by other pathogens, of which PRV is one of the common secondary infection pathogens. Porcine alveolar macrophages (PAMs) are the primary target cells of PRRSV, and their phagocytic function is critical for immune defense, homeostasis maintenance, and disease regulation. However, PRRSV disrupts PAMs phagocytosis, impairing the host’s ability to combat infection. This study used PRV-pAb complexes as phagocytic indicators, investigated the effect of PRRSV infection on PAMs phagocytosis and its underlying molecular mechanisms. We found that PRRSV infection interfered with phagosome maturation—a process regulated by Rab7 and other regulators, thereby blocking phagocytic degradation and significantly suppressing PAMs phagocytic activity. Further analysis revealed that reactive oxygen species (ROS) play a key role in this process. Elevated ROS levels damaged lysosomal membrane integrity, ultimately inhibiting phagosome-lysosome fusion. Notably, phagocytosis of PRRSV-infected PAMs was partially restored with N-acetylcysteine (NAC) by reducing ROS levels. These findings offer novel insights into PRRSV-induced immunosuppression and secondary infections while providing a theoretical foundation for developing more effective PRRSV prevention and control strategies.

African swine fever (ASF), caused by the African swine fever virus (ASFV), is an acute, febrile, highly contagious, and lethal disease that poses a severe threat to the global pig farming industry. Currently, no globally recognized, safe, and effective commercial ASF vaccine has been developed, making vaccination a crucial strategy for outbreak control. The ASFV structural proteins p72, p30, and p54 are key targets for vaccine development. In this study, we developed a novel baculovirus vector-based system for surface display of a recombinant protein comprising epitopes from p72, p30, and p54. Upon infection, the recombinant protein was expressed and anchored on the plasma membrane of Sf-9 cells. Purified virus analysis revealed that the Bac-recombinant protein enhanced gene delivery and transgene expression in mammalian cells compared to the Bac-Wild Type (Bac-WT). In a murine model, the Bac-recombinant protein induced significantly higher IFN-γ and IL-4 levels than Bac-p30 and the negative control. However, further evaluation in swine models is required to confirm its protective potential against ASFV. Furthermore, it also elicited a robust antibody response, generating high-titer Bac-recombinant protein-specific antibodies. Therefore, these findings suggest that the ASFV Bac-recombinant protein is a promising candidate for a vector-based vaccine.

African swine fever virus (ASFV) is a complex DNA virus and the only member of the Asfarviridae family. It causes high mortality and severe economic losses in pigs. The ASFV pB602L protein plays a key role in virus assembly and functions as a molecular chaperone of the major capsid protein p72. In addition, pB602L is an important target for the development of diagnostic tools for African swine fever (ASF) because it is a highly immunogenic antigen against ASFV. In this study, we expressed and purified ASFV pB602L and validated its immunogenicity in serum from naturally infected pigs with ASFV. Furthermore, we successfully generated an IgG2a κ subclass monoclonal antibody (mAb 7E7) against pB602L using hybridoma technology. Using western blot and immunofluorescence assays, mAb 7E7 specifically recognized the ASFV Pig/HLJ/2018/strain and eukaryotic recombinant ASFV pB602L protein in vitro. The ⁴⁷⁴SKENLTPDE⁴⁸² epitope in the ASFV pB602L C-terminus was identified as the minimal linear epitope for mAb 7E7 binding, with dozens of truncated pB602l fragments characterized by western blot assay. We also showed that this antigenic epitope sequence has a high conservation and antigenic index. Our study contributes to improved vaccine and antiviral development and provides new insights into the serologic diagnosis of ASF. Key points: • We developed a monoclonal antibody against ASFV pB602L, which can specifically recognize the ASFV Pig/HLJ/2018/ strain. • This study found one novel conserved B-cell epitope ⁴⁷⁴ SKENLTPDE ⁴⁸² . • In the 3D structure, ⁴⁷⁴ SKENLTPDE ⁴⁸² is exposed on the surface of ASFV pB602L, forming a curved linear structure.

The African swine fever (ASF) pandemics pose a significant threat to the global swine industry, and the development of safe and effective vaccines is a daunting but necessary challenge. The level and persistence of immunity are very important for the effectiveness of the vaccine. Targeting antigens to antigen presenting cells (APCs) can greatly enhance immunogenicity. In this study, we developed a self-assembled nano-ASFV vaccine candidate (NanoFVax) targeting DCs, by covalently coupling the self-assembled 24-mer ferritin with the dominant B and T cell epitopes of the highly immunogenic ASFV antigen (p72, CD2v, pB602L and p30) and fused with the chemokine receptor XCL1 (a DC targeting molecule) through the SpyTag/SpyCatcher protein ligase system. Compared to monomeric protein, the nanoparticle vaccines can induce a more robust T-cell response, and the high-level antibody response against ASFV can last for more than 231 days. Therefore, the NanoFVax is a novel and promising vaccine candidate for ASFV. Graphical Abstract

Objectives: Infectious bursal disease virus (IBDV) is a highly contagious, acutely infectious agent that causes immunosuppression in chickens. We expressed IBDV VP2 proteins in Escherichia coli (E. coli) to develop an effective virus-like-particles (VLPs) vaccine and evaluated its immunogenicity. Methods: The VLPs produced in E. coli were used as an immunogen mixed with a water-in-mineral-oil adjuvant (Montanide^TM ISA 71 VG, ISA 71 RVG) or a white oil (7#) adjuvant. VLPs without an adjuvant, commercial subunit vaccine, inactivated vaccine, and attenuated vaccine were used as controls. These test vaccines were intramuscularly injected into 19-day-old SPF chickens, which were challenged with the IBDV virulent strain at 30 days after vaccination. Results: The adjuvants boosted antibody production, and the adjuvant groups (except white oil) produced higher antibody levels than the non-adjuvanted controls and the commercial vaccine groups. In terms of cellular immunity, the VLPs plus adjuvant combinations produced higher levels of cytokines, IL-2, IL-4, and IFN-γ than the controls. Conclusion: IBDV VLPs plus the ISA 71 RVG adjuvant can be used as an optimal vaccine combination for improving the immune efficacy of IBD subunit vaccines, which can protect against the virulent strain.