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.

Immunochemical characterization of alkaline phosphatase from the fluid of sterile and fertile Echinococcus granulosus cysts.

Alkaline phosphatase (ALP) from hydatid cyst fluid (HCF) was purified and characterized for comparison between fertile and sterile HCF. Samples were obtained from slaughtered sheep and then sterile and fertile cysts were separated. ALP was purified from aspirated cyst fluid and biochemical parameters were determined. Sera from patients with hydatid disease (15 samples) and patients with other parasitic diseases including fascioliasis (2 samples), taeniasis ( Taenia saginata, 5 samples) and also sera from uninfected controls (15 samples), were collected and used in immunoblotting experiments with ALP from sterile and fertile HCF as antigen. Our results showed that ALP activity in fertile HCF [10.75+/-3.78 (SD) U/ml) was significantly more than in sterile HCF (6.25+/-2.43 U/ml). There were also some differences between the kinetic parameters and biochemical characteristics of ALP in fertile and sterile HCF. Immunoreactive bands were clearly observed when sera from hydatid infected patients were tested with ALP from fertile HCF as the antigen. However, this method revealed no cross-reaction between purified ALP from sterile HCF and sheep liver tissue. These findings suggest that there is some variation in the immunochemical characteristics of ALP from fertile and sterile HCF.