Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) is the pathogenic agent leading to COVID-19. Due to high speed of transmission and mutation rates, universal diagnosis and appropriate prevention are still urgently needed. The nucleocapsid protein of SARS-CoV-2 is considered more conserved than spike proteins and is abundant during the virus’ life cycle, making it suitable for diagnostic applications. Here, we designed and developed a fluorescent immunochromatography assay (FICA) for the rapid detection of SARS-CoV-2-specific antibodies using ZnCdSe/ZnS QDs-conjugated nucleocapsid (N) proteins as probes. The nucleocapsid protein was expressed in E.coli and purified via Ni-NTA affinity chromatography with considerable concentration (0.762 mg/mL) and a purity of more than 90%, which could bind to specific antibodies and the complex could be captured by Staphylococcal protein A (SPA) with fluorescence displayed. After the optimization of coupling and detecting conditions, the limit of detection was determined to be 1:1.024 × 10⁵ with an IgG concentration of 48.84 ng/mL with good specificity shown to antibodies against other zoonotic coronaviruses and respiratory infection-related viruses (n = 5). The universal fluorescent immunochromatography assay simplified operation processes in one step, which could be used for the point of care detection of SARS-CoV-2-specific antibodies. Moreover, it was also considered as an efficient tool for the serological screening of potential susceptible animals and for monitoring the expansion of virus host ranges.

A sensitive electrochemical immunosensor was prepared for rapid detection of ASA based on arsanilic acid (ASA) monoclonal antibody with high affinity. In the preparation of nanomaterials, polyethyleneimine (PEI) improved the stability of the solution and acted as a reducing agent to generate reduced graphene oxide (rGO) with relatively strong conductivity, thereby promoting the transfer of electrons. The dual conductivity of rGO and silver nanoparticles (AgNPs) improved the sensitivity of the sensor. The synthesis of nanomaterials were confirmed by UV-Vis spectroscopy, X-ray diffraction, transmission electron microscopy and scanning electron microscopy. In the optimal experiment conditions, the sensor could achieve the detection range of 0.50–500 ng mL⁻¹ and the limit of detection (LOD) of 0.38 ng mL⁻¹ (S/N = 3). Moreover, the sensor exhibited excellent specificity and acceptable stability, suggesting that the proposed sensor possessed a good potential in ASA detection. Thus, the as-prepared biosensor may be a potential way for detecting other antibiotics in meat and animal-derived foods.

Porcine parvovirus (PPV), a non-envelope single-stranded DNA virus, causes severe reproductive disorders in swine worldwide, characterized by fetal mortality, mummification, and reduced boar fertility. As a highly prevalent pathogen in Chinese swine herds, PPV imposes substantial economic burdens on intensive pig production systems. This review systematically synthesizes recent advances in PPV virology, focusing on genomic evolution of emerging strains (PPV1–PPV8), epidemiological dynamics of emerging strains, molecular pathogenesis, and novel diagnostic tools. Furthermore, we critically evaluate current vaccine strategies, highlighting their limitations in cross-protective efficacy and viral shedding control. By integrating multi-omics insights with immunological profiling, this work delineates actionable pathways for next-generation vaccine design and proposes a roadmap for rational antigen selection. This review consolidates foundational knowledge and establishes a translational bridge between basic virology and prevention and control of porcine parvovirus, addressing critical gaps in porcine reproductive disease management.

African swine fever virus (ASFV) is a highly pathogenic DNA virus that continues to circulate globally and poses a serious threat to the swine industry. However, the antigenic complexity of ASFV poses formidable challenges for vaccine and diagnostic development. The pE146L protein, which serves as a structural component of the inner envelope, is vitally required for efficient ASFV replication. In this study, the pE146L protein was expressed in E. coli Rosetta (DE3) cells, and five monoclonal antibodies (mAbs) were generated by immunizing BALB/c mice with the purified pE146L. Epitope fine mapping using a panel of truncated overlapping fragments identified five B-cell linear epitopes: aa37–45, aa65–80, aa86–94, aa86–101, and aa115–124, recognized by mAbs 8F3, 1B8, 5C10, 10F4, and 4B7, respectively. Furthermore, synthesized peptides SP1–SP5 were designed based on these sequences, wherein SP5 was prepared as an extended peptide spanning aa110–124 to potentially enhance antibody binding or peptide presentation. These synthetic peptides reacted not only with their respective mAbs but also with ASFV-positive pig sera, among which SP3 exhibited the strongest immunoreactivity. Sequence alignment revealed that all five epitopes were highly conserved among ASFV genotypes I, II, and the emerging I/II recombinant strains. Collectively, these findings identify novel antigenic epitopes of pE146L, providing preliminary candidates that may contribute to the future development of ASFV serological diagnostics.

African swine fever virus (ASFV) is the only member of the family Asfarviridae and can cause African swine fever, a disease with a consistently high mortality rate. The pE248R protein, a myristoylated integral membrane protein of ASFV, is required for virus infectivity and some early postentry event, making it a key target for studying the prevention and treatment of ASFV. In this study, BALB/c mice were immunized with purified recombinant pE248R protein, leading to the generation of five monoclonal antibodies (mAbs). Selected mAbs were subsequently subjected to further characterization. By identifying the reactivity of different pE248R protein peptide segments with these monoclonal antibodies, we screened and identified a linear B cell epitope (⁸⁷QEVALTQWMDAG⁹⁸) on the pE248R protein. These results provide a new theoretical basis for analyzing the structure and function of pE248R protein, particularly contributing to the construction of a comprehensive B-cell epitope map for ASFV immunogens.