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.

In recent years, food safety concerns associated with veterinary drug residues have aroused significant public attention, highlighting the critical need for continuous monitoring in both animal-derived foods and the environment to safeguard public health. Medroxyprogesterone acetate (MPA), a major anabolic steroid widely used in animal husbandry, poses potential human health risks according to recent studies. Although conventional analytical techniques based on chromatography and immunological assays are effective, they often suffer from complex operations, the need for skilled personnel, high cost, and time consumption. To overcome these limitations, electrochemical immunosensors modified with advanced nanomaterials offer a promising alternative. Herein, a highly sensitive electrochemical immunosensor was developed for trace MPA detection utilizing core–shell SiO₂-PEI@Ag nanoparticles as the sensing matrix. In this nanocomposite, the structural synergy between the SiO₂ core and outer Ag NPs shell not only provides a high-density platform for specific antibody immobilization, but also drastically expands the electroactive surface area and accelerates electron transfer to maximize signal amplification. Benefiting from these synergistic advantages, the constructed immunosensor exhibited a limit of detection (LOD) of 0.014 ng/mL and a wide linear range of 0.03–100 ng/mL. Furthermore, the recovery rates in pork and milk samples were 91.32–97.29% and 95.14–102.54%, respectively. In addition, negligible cross-reaction was observed toward structurally related steroid hormones related to MPA and common antibiotics. The immunosensor shows good stability, reproducibility, and accuracy, demonstrating great potential as a promising candidate to complement conventional tools for future MPA residue screening.

Pseudorabies virus (PRV), an important member of the Alphaherpesvirinae subfamily, shares high evolutionary homology with other members of the same subfamily, including human herpes simplex virus (HSV) and varicella‐zoster virus (VZV). However, significant differences exist among them in terms of host range, pathogenicity, and immune evasion strategies. This review systematically compares the roles of PRV, HSV type 1 (HSV‐1), and VZV in modulating host innate immune responses, encompassing the cyclic GMP‐AMP synthase (cGAS)‐stimulator of interferon genes (STING) signaling, RIG‐I‐like receptor (RLR) signaling, NOD‐like receptor (NLR) signaling, Toll‐like receptor (TLR) signaling, Janus kinase (JAK)‐signal transducer and activator of transcription (STAT) pathway, apoptosis, and autophagy. By summarizing and comparing the interactions of these three viruses with the host innate immune response, this review aims to provide a theoretical reference for understanding the conserved and unique mechanisms of immune evasion among alphaherpesviruses, and to offer insights for the development of novel antiviral strategies.