The efficacy of cercarial antigen loaded on nanoparticles as a potential vaccine candidate in Schistosoma mansoni-infected mice

Abstract

Schistosomiasis is one of the most common causes of morbidity and mortality from parasitic diseases. Mass treatment has proven to be insufficient because of repeated infection after treatment and the appearance of strains resistant to drug therapy. Hence, immunization is a new approach to control the disease and limit the pathological consequences of schistosomiasis. To evaluate the prophylactic effect of Cercarial antigen (CAP) loaded on chitosan nanoparticles (CSNPs) as a potential vaccine against Schistosoma mansoni-infected mice. 130 mice divided into 2 groups were used: Group I: Control groups (50 mice) subdivided into subgroup Ia (10 mice): Non-infected mice (normal control), subgroup Ib (20 mice): Schistosoma infected mice (infected control) and subgroup Ic (20 mice): Non-infected mice receiving NPs only. Group II: Vaccinated group (80 mice) subdivided equally into subgroup IIa (CAP): Received cercarial antigen and subgroup IIb (CAP + CSNP): Received cercarial antigen loaded on chitosan NPs then both vaccinated groups were infected with S. mansoni 3 weeks following the initial vaccination dose. CAP + CSNP and CAP groups showed significant reduction in adult worms count, hepatic egg count, hepatic granulomas number and size in comparison to the infected control group. Elevation of serum IgG and IgM levels, CD4⁺ and CD8⁺ T cell frequencies, IL-4, IL-10 and INF-γ levels was more significant in CAP + CSNP group than CAP group. CAP + CSNP is a promising new preparation of Schistosomal antigens that gave better results than immunization with CAP alone. CSNPs enhanced the immune and protective effect of CAP as validated by parasitological, histopathological and immunohistochemical studies.

Keywords: CAP; Chitosan nanoparticles; Flow cytometry; Immunization; Schistosomiasis mansoni.

Fig. 1

A photomicrograph of liver sections of mice (H&E × 200). A Normal control group (GIa) B Chitosan group (GIc) show normal liver architecture. C Infected control group at 6 weeks P.I.: multiple large schistosomal granulomas around viable ova. D Infected control group at 8 weeks P.I.: multiple granulomas mainly fibrocellular and fibrous surrounding schistosomal ova. E Infected control group at 10 weeks P.I.: multiple schistosomal granulomas mainly fibrocellular and fibrous coalescent with each other around multiple ova. F Infected control group at 12 weeks P.I.: multiple granulomas mainly fibrous coalescent with each other surrounding schistosomal ova

Fig. 2

A photomicrograph of liver sections of mice of the CAP vaccinated group (GIIa) at different durations (H&E × 200): A 6 weeks P.I.: a granuloma surrounding a schistosome ovum B 8 weeks P.I.: fibrocellular granulomas surrounding schistosomal eggs. C 10 weeks P.I.: a small fibrocellular schistosomal granuloma around multiple ova. D 12 weeks P.I.: a reduction in the size of the cellular schistosomal granuloma

Fig. 3

A photomicrograph of liver sections of mice of the CAP + CSNP vaccinated group (GIIb) at different durations (H&E × 200): A 6 weeks P.I.: a small granuloma surrounding a schistosomal ovum. B 8 weeks P.I.: a very small fibrocellular granuloma surrounding a schistosomal ovum. C 10 weeks P.I.: a small fibrocellular schistosomal granuloma. D 12 weeks P.I.: a marked reduction in the size of the cellular schistosomal granulomas

Fig. 4

A photomicrograph of liver sections obtained from Schistosoma mansoni-infected mice (GIb) (Masson trichrome stain × 200): A 6 weeks P.I.: the granuloma was many cellular. B 8 weeks P.I. and C 10 weeks P.I.; the granuloma was fibrocellular. D 12 weeks P.I.: the granulomas were mainly fibrous with marked increase in the fibrous content

Fig. 5

A photomicrograph of liver sections obtained from mice of CAP group (GIIa) at different durations (Masson trichrome stain × 200): A 6 weeks P.I.: the Schistosome granuloma was mainly cellular. B 8 weeks P.I. and C 10 weeks P.I.: a reduction in the fibrous content of the schistosome granulomas. D 12 weeks P.I.: more reduction in the fibrous content of the schistosome granulomas

Fig. 6

A photomicrograph of liver sections obtained from mice of CAP + CSNP group (GIIb) at different duartions (Masson trichrome stain × 200): A 6 weeks P.I.: the granuloma was mainly cellular. B 8 weeks P.I. and C 10 weeks P.I.: a reduction in the fibrous content of the granulomas. D 12 weeks P.I.: marked reduction in the fibrous content of the granulomas

Fig. 7

The relation between IgM and IgG serum levels (mg/ml) in the studied groups at different durations P.I

Fig. 8

The relation between CD4⁺ T and CD8⁺ T cells levels in the studied groups at different durations P.I

Fig. 9

The relation between IL-4, IL-10 and IFN-γ serum levels (pg/ml) in the studied groups at different durations P.I