Identification of Potential Druggable Targets and Structure-Based Virtual Screening for Drug-like Molecules against the Shrimp Pathogen Enterocytozoon hepatopenaei

Development of a colloidal gold immunochromatographic strip for the rapid on-site detection of Ecytonucleospora hepatopenaei (EHP)

The Pacific white shrimp (Penaeus vannamei), one of the world's most economically important aquatic species, is highly susceptible to Ecytonucleospora hepatopenaei (EHP), a pathogen that infects the hepatopancreas and causes hepatopancreatic microsporidiosis (HPM), leading to stunted growth and substantial economic losses in shrimp farming. Currently, no effective treatments for EHP exist, making rapid on-site detection and preventive measures essential for disease control. While nucleic acid-based detection methods are commonly employed, they require specialized equipment, controlled environments, and trained personnel, which increase costs. To address this limitation, we developed a colloidal gold immunochromatographic assay (GICA) strip for rapid on-site detection of EHP in shrimp farms. Using LC-MS/MS, 15 high-abundance EHP proteins were identified, with EhSWP3 ranked highest and selected as the optimal antigen detection target. Recombinant EhSWP3 was used to immunize mice, resulting in the development of monoclonal antibodies. The optimal capture and labeled antibody combination (1B6, 3A6) was identified and incorporated into the GICA strip. Testing with common shrimp pathogens and various microsporidia samples demonstrated the high specificity of the EHP test strip. The strip exhibited a sensitivity of 1.81 × 103 copies of the EHP-SSU rRNA gene for detecting EHP-infected shrimp and 1 × 104 purified EHP spores, indicating its strong sensitivity in practical applications. To facilitate on-site use, a simple GICA workflow was established using disposable pestles, Buffer A, and Buffer B, enabling detection within 15 min. Testing of 110 shrimp samples revealed a 90.0 % concordance between the GICA strip and qPCR results. This study marks the first development and application of an EHP antigen detection strip, offering a practical tool for rapid, on-site disease monitoring in shrimp farming.

Overcoming research challenges: In vitro cultivation of Ameson portunus (Phylum Microsporidia)

Ameson portunus is an intracellular pathogen that infects marine crabs Portunus trituberculatus and Scylla paramamosain, causing significant economic losses. However, research into this important parasite has been limited due to the absence of an in vitro culture system. To address this challenge, we developed an in vitro cultivation model of A. portunus using RK13 cell line in this study. The fluorescent labeling assay indicated a high infection rate (∼60 %) on the first day post-infection and quantitative PCR (qPCR) detection demonstrated successful infection as early as six hours post-inoculation. Fluorescence in situ hybridization (FISH) and qPCR were used for the detection of A. portunus infected cells. The FISH probe we designed allowed detection of A. portunus in infected cells and qPCR assay provided accurate quantification of A. portunus in the samples. Transmission electron microscopy (TEM) images revealed that A. portunus could complete its entire life cycle and produce mature spores in RK13 cells. Additionally, we have identified novel life cycle characteristics during the development of A. portunus in RK 13 cells using TEM. These findings contribute to our understanding of new life cycle pathways of A. portunus. The establishment of an in vitro culture model for A. portunus is critical as it provides a valuable tool for understanding the molecular and immunological events that occur during infection. Furthermore, it will facilitate the development of effective treatment strategies for this intracellular pathogen.

Lead generation of UPPS inhibitors targeting MRSA: Using 3D-QSAR pharmacophore modeling, virtual screening, molecular docking, and molecular dynamic simulations

Undecaprenyl Pyrophosphate Synthase (UPPS) is a vital target enzyme in the early stages of bacterial cell wall biosynthesis. UPPS inhibitors have antibacterial activity against resistant strains such as MRSA and VRE. In this study, we used several consecutive computer-based protocols to identify novel UPPS inhibitors. The 3D QSAR pharmacophore model generation (HypoGen algorithm) protocol was used to generate a valid predictive pharmacophore model using a set of UPPS inhibitors with known reported activity. The developed model consists of four pharmacophoric features: one hydrogen bond acceptor, two hydrophobic, and one aromatic ring. It had a correlation coefficient of 0.86 and a null cost difference of 191.39, reflecting its high predictive power. Hypo1 was proven to be statistically significant using Fischer's randomization at a 95% confidence level. The validated pharmacophore model was used for the virtual screening of several databases. The resulting hits were filtered using SMART and Lipinski filters. The hits were docked into the binding site of the UPPS protein, affording 70 hits with higher docking affinities than the reference compound (6TC, - 21.17 kcal/mol). The top five hits were selected through extensive docking analysis and visual inspection based on docking affinities, fit values, and key residue interactions with the UPPS receptor. Moreover, molecular dynamic simulations of the top hits were performed to confirm the stability of the protein-ligand complexes, yielding five promising novel UPPS inhibitors.