Characterization of cellular and humoral immune responses to alkaline phosphatase from fertile hydatid cysts in the human peripheral blood.

Hydatid cyst, the larval stage of the tapeworm Echinococcus granulosus and a causative agent of cystic echinococcosis, possesses a vast number of antigenic peptides that are constantly presented in the host immune system during infection. Here, we sought to provide more information about the cellular/humoral components engaged in the peripheral immune reactions to the fertile-cyst-derived Echinococcus alkaline phosphatase (E.ALP) in human hosts. Lymphoproliferative and cytokine responses after recall of E.ALP suggested the presence of specific immune reactions against the antigen. Interferon gamma (IFN-γ), tumor necrosis factor alpha (TNF-α), and interleukin (IL)-10 had the highest fold increase over the spontaneous levels in response to hydatid crude antigen (HCA). Recall of E.ALP, as well as its encounter, boosted IFN-γ, TNF-α, IL-2, and IL-6 responses in peripheral blood mononuclear cells cultures (PBMCs). The HCA-driven levels of all the cytokines in the culture supernatants of normal PBMCs were higher than those measured after E.ALP encounter. Immunoglobulin G (IgG)-profile in response to HCA showed the dominance of specific IgG1, IgG2, and IgG4 antibodies, but relatively lower affinity of IgG3 to this antigen. IgG1 and IgG3 were the only isotypes detected in serum responses to E.ALP. Our findings suggested that E.ALP contributes to the early phase of immune responses to the parasite, likely by induction of proinflammatory profiles and clonal expansion of high-affinity IgG1- and IgG3-secreting plasma cells, suggesting the value of E.ALP as a candidate to develop novel therapeutic and immunization strategies.