Acta Biochimica et Biophysica Sinica•2026•DOI: 10.3724/abbs.2026043
Pentatrichomonas hominis is a zoonotic protozoan belonging to the family Trichomonadidae that primarily inhabits the cecum and colon. Although traditionally regarded as an opportunistic pathogen, P. hominis is increasingly recognized for its pathogenic potential, including roles in animal diarrheal disease and the induction of intestinal epithelial damage and chronic inflammation in mice. A previous study further identified a significant correlation between P. hominis infection and colorectal cancer, underscoring its growing clinical and public health significance. This parasite infects a wide range of hosts, among which dogs, displaying infection rates as high as 47.4%, are regarded as a potential zoonotic reservoir because of their close contact with humans. Consequently, establishing reliable detection methods for P. hominis in dogs is essential for veterinary practice and public health surveillance. Current methods for detecting P. hominis infections in dogs mainly include direct smear microscopy and polymerase chain reaction (PCR)-based techniques. Although direct smear microscopy is straightforward, it frequently exhibits low sensitivity. In comparison, PCR demonstrates high sensitivity and specificity, yet it relies on specialized equipment, trained operators, and extended processing time. Recently, reported nucleic acid detection approaches, such as recombinase polymerase amplification coupled with lateral flow dipstick (RPA-LFD) and RPA-CRISPR/Cas12a assays, have enhanced the efficiency and accessibility of molecular detection for P. hominis. However, these methods still necessitate nucleic acid extraction, controlled temperature conditions, and operational complexity. In addition, some emerging detection technologies, such as microfluidic chips and nanozyme-based detection systems, offer advantages of high throughput and sensitivity but have not yet been widely applied in the field of detection of parasitic infection. Although immunoassays, including enzyme-linked immunosorbent assay (ELISA) and colloidal gold immunochromatographic strips, have been successfully used for the detection of infections of some intestinal protozoans, such as Giardia, there have been no reports on their application for detecting P. hominis infections, primarily due to the lack of specific detection antigens. To address the detection need, liquid chromatography-tandem mass spectrometry (LC-MS/MS) was used as the primary discovery tool to identify specific detected antigens. Using this targeted proteomics approach, we precisely identified immunoreactive proteins and selected glyceraldehyde 3 phosphate dehydrogenase (GAPDH), an immunogenic and species-specific antigen in related parasites, as the candidate antigen. Based on this identified antigen, we subsequently developed and evaluated the detection performance in both indirect ELISA and colloidal gold immunochromatographic strips using recombinant GAPDH. This study aimed to identify novel antigens for immunodetection of P. hominis and to establish a practical, on-site method for detecting dog infections, thereby facilitating further epidemiological and clinical research.
Acta Biochimica et Biophysica Sinica•2025•DOI: 10.3724/abbs.2025019
Cancer cells evade immune detection through checkpoint molecules like PD-L1 and PD-L2 which suppress T-cell activation. While PD-L1 is well-studied, the role of PD-L2 remains unclear. Pyruvate kinase M2 (PKM2), a metabolic enzyme, influences immune checkpoint regulation, but its role in PD-L1 and PD-L2 modulation is not well defined. Here, we investigate the role of pyruvate kinase M2 (PKM2) in modulating the immune checkpoint molecules PD-L1 and PD-L2 via GATA3 in cancer cells, with insights from both human and mouse models. We find that PKM2 enhances PD-L1 expression while inhibiting PD-L2, a dual regulatory mechanism that facilitates immune evasion. Knockdown and overexpression experiments revealed GATA3 as a key mediator. PKM2 knockout reduced GATA3 level, leading to decreased PD-L1 and increased PD-L2 expression. Chromatin immunoprecipitation (ChIP)-qPCR demonstrates that GATA3 functions as a direct transcription factor capable of binding to the promoters of PD-L1 and PD-L2. In silico analyses of 81 esophageal squamous cell carcinoma (ESCC) cases from the TCGA database demonstrate that PKM2 mRNA is unrelated to PD-L1 and PD-L2 expression but is negatively correlated with CD8+ T-cell infiltration in ESCC. To further validate these findings, we establish a xenograft model using immune-competent C57/BL6N mice, where knockdown of PKM2 results in significant downregulation of both PD-L1 and PD-L2 expression. Collectively, these findings underscore the divergent roles of PKM2 in regulating immune checkpoint expression in human and mouse cancer models and suggest that targeting the PKM2-GATA3 axis could enhance cancer immunotherapy by fine-tuning PD-L1 and PD-L2 levels.
Acta Biochimica et Biophysica Sinica•2026•DOI: 10.3724/abbs.2026043
Pentatrichomonas hominis is a zoonotic protozoan that primarily inhabits the cecum and colon of dogs, with infection rates as high as 47.4%, posing a significant public health risk due to close human contact. Current detection methods, including direct smear microscopy and PCR, have limitations in sensitivity, equipment requirements, and operational complexity. To address the need for a practical on-site detection method, we employed liquid chromatography-tandem mass spectrometry (LC-MS/MS) to identify specific antigens from P. hominis excretory-secretory (ES) proteins. Glyceraldehyde 3-phosphate dehydrogenase (GAPDH) was selected as a candidate antigen due to its high immunogenicity and species specificity. The GAPDH gene was cloned and expressed in E. coli, and the recombinant protein was purified. Mouse anti-GAPDH serum was generated, and its reactivity was confirmed by Western blot and indirect ELISA (titer 1:102,400). Immunofluorescence localization showed GAPDH in the cytoplasm of P. hominis trophozoites. Based on this antigen, we developed a colloidal gold immunochromatographic strip for rapid detection of P. hominis in dogs. The strip demonstrated high sensitivity and specificity, providing a practical tool for veterinary diagnosis and epidemiological surveillance. This study is the first to report an immunochromatographic strip for P. hominis detection, offering a rapid, user-friendly alternative to existing methods.
Acta Biochimica et Biophysica Sinica•2025•DOI: 10.3724/abbs.2025019
Cancer cells evade immune detection through checkpoint molecules PD-L1 and PD-L2, which suppress T-cell activation. While PD-L1 is well-studied, the role of PD-L2 remains unclear. Pyruvate kinase M2 (PKM2), a metabolic enzyme, influences immune checkpoint regulation, but its role in PD-L1 and PD-L2 modulation is not well defined. Here, we investigate the role of PKM2 in modulating PD-L1 and PD-L2 via GATA3 in cancer cells, with insights from both human and mouse models. We find that PKM2 enhances PD-L1 expression while inhibiting PD-L2, a dual regulatory mechanism that facilitates immune evasion. Knockdown and overexpression experiments revealed GATA3 as a key mediator. PKM2 knockout reduced GATA3 level, leading to decreased PD-L1 and increased PD-L2 expression. Chromatin immunoprecipitation (ChIP)-qPCR demonstrates that GATA3 functions as a direct transcription factor capable of binding to the promoters of PD-L1 and PD-L2. In silico analyses of 81 esophageal squamous cell carcinoma (ESCC) cases from the TCGA database demonstrate that PKM2 mRNA is unrelated to PD-L1 and PD-L2 expression but is negatively correlated with CD8+ T-cell infiltration in ESCC. To further validate these findings, we establish a xenograft model using immune-competent C57/BL6N mice, where knockdown of PKM2 results in significant downregulation of both PD-L1 and PD-L2 expression. Collectively, these findings underscore the divergent roles of PKM2 in regulating immune checkpoint expression in human and mouse cancer models and suggest that targeting the PKM2-GATA3 axis could enhance cancer immunotherapy by fine-tuning PD-L1 and PD-L2 levels.