Immune responses to viable and degenerative metacestodes of Taenia solium in naturally infected swine

Abstract

Neurocysticercosis, caused by the larvae of the pork tapeworm Taenia solium, is the most common helminth infection of the CNS in humans worldwide. There is no existing animal model of neurocysticercosis that resembles human infection. To overcome this limitation, swine (the natural intermediate host of the parasite) may be a suitable model. The immune response associated with different stages of the parasite larva (metacestode) has not yet been explored. Therefore, we investigated the immune response to various stages of the metacestode (cyst) in the brain and muscles of naturally infected swine. Swine with neurocysticercosis (n=10) and healthy controls (n=10), as confirmed by magnetic resonance imaging, were included in this study. The animals were sacrificed, and the tissues containing viable or degenerative metacestods in the brain and infected muscles were collected and subjected to reverse transcriptase-PCR and ELISA to determine the expression of different cytokines (IFN-γ, TNF-α, IL-1β, IL-2, IL-4 IL-6, IL-8 and IL-10). Higher expression of IL-10 was found to be associated with viable cysts. Degenerating cysts displayed significantly increased levels of IFN-γ, TNF-α, IL-1β, IL-2, IL-6 and IL-8, whereas calcified cysts had elevated levels of IL-4, IL-10, TNF-α and IL-6. The present study indicated a strong regulatory (IL-10) and Th1 cytokine response in viable and degenerating cysts, respectively, whereas calcified cysts had a mixed anti-inflammatory (IL-4), regulatory (IL-10) and pro-inflammatory (TNF-α and IL-6) response. Thus, Th1 and Th2 immune response operate in the vicinity of metacestodes and the type of immune response may be responsible for disease severity.