Human leukocyte extract enhances albendazole efficacy against Echinococcus multilocularis in mice by reducing parasitic microRNAs, myeloid and lymphoid immunosuppressive cells

BACKGROUND: Echinococcus multilocularis induces a serious zoonotic infection in humans and growth of metacestodes is associated with immunosuppression and tolerance. Current treatment relies almost exclusively on albendazole, a parasitostatic drug with variable clinical efficacy. Human low molecular weight leukocyte extract (HLE) has been shown to modulate innate and adaptive immunity at various diseases and can serve as promising and safe adjuvant to chemotherapy. METHODOLOGY: In the present study we investigated the effects of albendazole (ABZ), human leukocyte extract (HLE) and their combination on murine alveolar echinococcosis, developing in the peritoneal cavities, by monitoring cysts weight, levels of circulating parasitic miRNAs, cytokine levels by ELISA and qPCR, the proportions of lymphoid and myeloid cells in spleens and peritoneal cavities by flow cytometry and proliferation of T and B lymphocytes and NO production ex vivo. PRINCIPAL FINDINGS: Albendazole therapy moderately reduced cyst mass, selectively altered circulating parasite-derived miRNA levels in line with moderate decrease of IL-10 and TGF-β and myeloid-derived suppressor cells without the effects on suppressed T and B cells proliferation and high NO production. HLE in combination with ABZ significantly reduced peritoneal cyst growth and these two therapies markedly decreased circulating parasite derived microRNAs and expression of T- and B-regulatory cells lineage-specific transcription factors. These molecular changes were accompanied by a marked restoration of T and B lymphocyte proliferation, significant decline of regulatory IL-10 and TGF-β cytokines and immunosuppressive myeloid cells and MHC IIlow (M2) macrophages in spleens and peritoneal cavities, where HLE and ABZ + HLE interventions suppressed NO production and altered cytokine expression. The effect probably involved NF-κB downregulation, preventing excessive inflammation while enhancing ABZ efficacy. CONCLUSIONS: HLE as adjuvant enhanced albendazole efficacy against Echinococcus multilocularis infection in mice via reduction of T regulatoty type of response and MDSC expansion and shift of systemic and local immunity toward balanced Th1/Th2- biased profiles. The marked reduction in circulating parasite-derived miRNAs identifies a previously unrecognised mechanism that may contribute to the immunomodulatory effects of HLE and highlights these molecules as potential biomarkers of therapeutic response. Collectively, these results propose HLE as a promising adjunct immunotherapeutic candidate capable of counteracting parasite-induced immunosuppression and potentiating benzimidazole chemotherapy.