Niosome-Based Vaccine Against Experimental Cystic Echinococcosis: Histological and Biochemical Evaluation.

Cystic echinococcosis (CE), a neglected zoonotic disease caused by E. granulosus, imposes significant morbidity and economic burdens worldwide. Nanoparticle-based delivery systems offer a promising strategy to enhance vaccine efficacy. This study evaluated a novel niosomal delivery system for protoscolex antigen (PSAg) against experimental CE. Rabbits (n=5/group) were randomized into two main groups: Group I (controls) consisting of subgroup Ia (non-infected, non-vaccinated negative controls) and Ib (infected, non-vaccinated positive controls); and Group II (vaccinated), comprising subgroup IIa (PSAg alone), IIb (PSAg-loaded niosomes), and IIc (niosomes alone). The animals were challenged intraperitoneally with 3,000 E. granulosus protoscolices after receiving two subcutaneous doses (100 µg) at three weeks apart. Parasitological, histopathological, and immunohistochemical (PCNA) studies, alongside serological profiling (IgG, IFN-γ, IL-10) were used to assess vaccine efficacy. PSAg-loaded niosomes significantly reduced liver/lung hydatid cyst development compared to controls. This protection was associated with improved histopathological scores, decreased PCNA expression, and a polarized Th1 immune response (elevated IgG and IFN- γ; reduced IL-10). These findings suggest that niosomal encapsulation markedly enhances the immunogenicity of PSAg, positioning it as a potent vaccine candidate for CE control.