Echinococcus multilocularis specific antibody, systemic cytokine, and chemokine levels, as well as antigen-specific cellular responses in patients with progressive, stable, and cured alveolar echinococcosis: A 10-year follow-up

Background

The infestation with Echinococcus multilocularis larvae may persist in humans for up to decades without evident clinical symptoms. Longitudinal investigations are needed to understand the dynamic immunological processes in alveolar echinococcosis (AE) patients associated with an active and progressive, a stable or a regressive course of disease.

Methodology/Principal findings

This study evaluated the E. multilocularis specific antibody responses, systemic cytokine, and chemokine serum levels over a 10-year follow-up period, as well as cellular responsiveness in AE patients. Our results demonstrate a rapid decrease in antibodies against E. multilocularis specific antigen Em2+. Especially in cured patients, these antibodies remained negative, making them a significant predictor for cured AE. E. multilocularis specific IgG4, and indirect hemagglutination IHA decreased later in time, after around 5 years. While total IgE did not show significant dynamics over the course of disease, E. multilocularis specific IgE decreased after one to two years, and increasing levels were a significant predictor of progressive disease. There was no significant change in systemic IL-8, IL-9, CCL18 or CCL20 serum levels over time. Univariate analysis across groups indicated lower IL-8 levels in cured patients; however, this result could not be confirmed by multivariate analysis. Levels of CCL17 decreased during treatment, especially in cured patients, and thus might serve as a predictive or risk factor for progressive disease. Levels of IL-10 and CCL13 decreased during disease, especially after five and ten years of intervention. The E. multilocularis antigen (EmAg) inducible cellular productions of MCP1(CCL13), TARC(CCL17) and PARC(CCL18) were lowest in patients with cured AE and infection-free controls, while the EmAg inducible cellular production of IFN-γ increased after cure. Significant positive cytokine and chemokine correlations were observed in AE patients for IL-9, IL-10, CCL13(MCP-4), CCL17(TARC) and CCL20(LARC)(for all p<0.001). E. multilocularis specific IgG4 response correlated positively with TARC (p<0.001). Both markers enhanced over time in progressive disease and decreased after cure. The levels of IL-8, IL-10, MCP4 and LARC enhanced with AE regression.

Conclusions/Significance

Repeated biomarker surveys are advisable to evaluate progression or regression of disease during longitudinal follow-up and such analyses can support imaging techniques and improve staging of AE patients.

Alveolar echinococcosis (AE) is a severe disease caused by Echinococcus multilocularis, the fox tapeworm. Humans exposed to E. multilocularis may develop severe AE with progressive tissue and organ infiltrating growth of the larval stage. The E. multilocularis larvae appear to have developed effective immune evasion mechanisms which facilitate an asymptomatic incubation and an extended host and parasite coexistence for decades. Over a 10-year follow-up, this investigation aimed to gain a better understanding of the immunological process associated with an active and progressive, a stable or a regressive course of AE. In summary, the rapid decrease of antibodies against the E. multilocularis specific antigen Em2+, especially in cured patients, makes them a significant predictor for cured AE. The positive relation of E. multilocularis specific IgG4 responses and chemokine levels of TARC can indicate AE progression when both enhance over time. Enhanced levels of cytokines IL-8, IL-10, and chemokines MCP4 and LARC may predict AE regression. Repeated biomarker surveys are advisable to evaluate progression or regression of AE during longitudinal follow up, and such analyses can support imaging techniques and improve staging of AE patients.

The effects of taxanes, vorinostat and doxorubicin on growth and proliferation of Echinococcus multilocularis metacestodes assessed with magnetic resonance imaging and simultaneous positron emission tomography

Cytostatic drugs used in cancer therapy were evaluated for their capacity to inhibit Echinococcus multilocularis metacestode growth and proliferation. Metacestode tissues were exposed in vitro to docetaxel, doxorubicin, navelbine, paclitaxel, and vorinostat for 1 week, then incubated in drug-free culture, and thereafter metacestodes were injected into the peritoneum of Meriones unguiculatus. Magnetic resonance imaging (MRI) and simultaneous positron emission tomography (PET) were applied to monitor in vivo growth of drug-exposed E. multilocularis in Meriones. At 3 month p.i., docetaxel (at 10 μM, 5 μM and 2 μM) inhibited in vivo growth and proliferation of E. multilocularis, and at 5 months p.i., only in the 2 μM docetaxel exposure group 0.3 cm ³ of parasite tissue was found. With paclitaxel and navelbine the in vivo growth of metacestodes was suppressed until 3 months p.i., thereafter, parasite tissues enlarged up to 3 cm ³ in both groups. E. multilocularis tissues of more than 10 g developed in Meriones injected with metacestodes which were previously exposed in vitro to doxorubicin, navelbine, paclitaxel or vorinostat. In Meriones infected with metacestodes previously exposed to docetaxel, the in vivo grown parasite tissues weighted 0.2 g. In vitro cultured E. multilocularis metacestodes exposed to docetaxel did not produce vesicles until 7 weeks post drug exposure, while metacestodes exposed to doxorubicin, navelbine and vorinostat proliferated continuously. In summary, docetaxel, and less efficaciously paclitaxel, inhibited in vivo and in vitro parasite growth and proliferation, and these observations suggest further experimental studies with selected drug combinations which may translate into new treatment options against alveolar echinococcosis.