Monoclonal antibody-based immunohistochemistry reveals residual Taenia solium antigens in calcified granulomas from pigs with neurocysticercosis

Neurocysticercosis (NCC), a parasitic brain infection caused by Taenia solium larvae, remains a leading cause of preventable epilepsy globally. Although calcified brain lesions were formerly considered as the quiescent end stage of NCC, they may act as epileptogenic foci. It has been suggested that parasitic antigens within calcified lesions may act as potential triggers of inflammation and subsequent seizure activity. In this study, we developed and optimized immunohistochemistry (IHC) assays employing anti-Taenia solium monoclonal antibodies (mAbs) to detect residual cyst antigens in calcified lesions in a porcine NCC model and assessed antigen persistence for up to 12 months after successful antiparasitic treatment. Six mAbs raised against T. solium whole cyst (TsW5, TsW8, and TsW12), vesicular fluid (TsV3 and TsV4), and excretory/secretory products (TsE1) were used for IHC assay development and tested in brain sections containing viable brain cysts from NCC pigs and uninfected tissue from controls to optimize assay conditions, blocking, primary and secondary antibody dilutions. Optimized assays were subsequently performed in selected calcified granulomas (n = 20) obtained from NCC-infected pigs sacrificed at 4, 8, and 12 months after antiparasitic treatment to identify residual cyst antigens as well as their localization and area of reactivity. We observed residual cyst antigens in 65–80% of calcified granulomas, with TsW8 and TsV3 showing the highest percentages of immunoreactivity. Antigen localization followed two patterns, one with antigens entirely located within the calcified lesions (TsW5, TsW8, TsW12, and Tsv4) and another with antigens located outside the cyst in the perilesional brain tissue (TsV3 and TsE1). Antigen detection and the extent of reactivity declined progressively after antiparasitic treatment but persisted at detectable immunoreactive areas in calcified granulomas up to month 12 months after treatment. T. solium antigens remain detectable in calcified granulomas and in the perilesional tissue for up to 12 months after antiparasitic treatment in the pig model.