Impact of Induced Th1/Th2 Shift on Trichobilharzia regenti Infection in Mice

Bird schistosomes parasitize mammals as non-specific hosts. Neurotropic Trichobilharzia regenti migrates extravasally via nervous tissue in experimentally infected mice. The majority of successfully penetrated larvae remain in the skin; the rest migrate through peripheral nerves to the spinal cord and brain. The potential of schistosomula to leave the skin and enter the central nervous system vary, and may be associated with Th1/Th2 polarization of the host cell immune response. The aim of the present study was to evaluate the impact of induced shift in polarization of cell immune response on the migration of T. regenti larvae in mammals. For this purpose, non-specifically immunomodulated mice were infected. The localization and abundance of schistosomula and associated histopathological changes were followed using routine histological techniques. Markers characterizing Th1 and Th2 systemic immune responses were followed using flow cytometry. The study revealed that the shift towards Th1 response at the time of infection correlates with the speed and intensity of schistosomula migration towards the brain and with the severity of accompanying pathologies. This indicates increased health risks associated with T. regenti infection for mammals (potentially including human) with previously modulated cell immune response that may occur under natural conditions, e.g. due to the exposure to another infectious agent.