Exploring the functional and immunological diversity of the fatty acid-binding protein (FABP) family in Fasciola hepatica

This study aimed to investigate the role of Fasciola hepatica fatty acid-binding proteins (FhFABPs). All seven FhFABP isoforms were successfully cloned, and six were recombinantly expressed using a yeast expression system. To assess the functions of individual isoforms, various methods were employed, including real-time PCR, ELISA, ANS displacement assays, and cell culture experiments using monocyte-derived dendritic cells (moDCs) treated with FhFABPs. A quantitative analysis of fabp isoform gene expression across different developmental stages was performed using real-time PCR. RNA isolated from eggs, metacercariae, newly excysted juveniles (NEJs), and adult worms served as templates, with isoform-specific primers used for each FABP (Figure3_Figure4). Sheep sera collected from animals experimentally challenged with Fasciola hepatica were used to assess IgG antibody responses against FhFABPs using the ELISA method (Figure5). An ANS displacement assay using selected fatty acids was also conducted to evaluate the binding affinity of fatty acids to FhFABPs (Figure6). In the supernatants from cell cultures treated with FhFABPs, cytokine and chemokine levels were measured using ELISA (Figure7), while cell surface markers were analyzed by flow cytometry (FigureS4). Quantitative gene expression analysis revealed distinct, stage-specific expression patterns, with the highest levels observed in adult flukes. Functional assays demonstrated isoform-specific variations in fatty acid binding, indicating potential adaptations to host environments. Immunological evaluations highlighted the variable immunogenicity of FhFABPs and their capacity to modulate human dendritic cell responses in an isoform-dependent manner. Collectively, these findings underscore the critical roles of FhFABPs in nutrient acquisition, immune modulation, and parasite survival. Their involvement in pathogenesis and immune evasion positions them as promising candidates for the development of vaccines, diagnostic tools, and novel immunomodulatory therapies.