Ultrastructural changes of adult Schistosoma mansoni worms recovered from C57BL/6 mice passively immunized with normal and vaccinated rabbit sera in vivo

Abstract

The purpose of the study is to explore the role of humoral immunity against Schistosoma mansoni infection in C57BL/6 mice using highly resistant rabbits that had been exposed to three separate immunizations with ultraviolet (UV)-irradiated cercariae (8,000 attenuated cercariae/rabbit in each immunization), and their sera were tested for their ability to transfer protection against S. mansoni challenge. The present study showed the reduction in challenge worm burden had reached 32.76-43.64% when compared with recipients of normal serum or no serum. The surface topography of the worms collected from immunized mice with either normal rabbit sera (NRS) or vaccinated rabbit sera (VRS) revealed severe tegumental alterations, especially in the VRS group. Worms collected from groups that were immunized by NRS or VRS postinfection (200 normal cercariae/mouse) by day 42. Worms from group immunized with NRS showed damage in the tegument, characterized by severe swelling or erosion of tegumental folds, accompanied by changes in tubercles, swelling, shortening, and loss of spines in male worms. The alteration in female tegument was characterized by swelling of tegumental folds, atrophy of ventral sucker, damage of sensory papillae along all the body, severe peeling in some regions, and appearance of few small blebs. VRS induced more severe tegumental damage than NRS in both male and female worms. Severe shrunken vesicles were protruded from the surface between the two suckers. The tegument of the male showed a collapse of tubercles followed by the appearance of vesicles on their surfaces, fusion, erosion, and superficial focal peeling of tegumental folds. In the female worms, severe damage to the oral sucker, the surface between the two suckers, extensive peeling, severe swelling of the tegument, and damage of sensory papillae. In conclusion, the present study support the hypothesis that high levels of antibodies were developed in rabbit sera after multiple exposures to attenuated cercariae of S. mansoni. Furthermore, immunization might have transferred protection against the infection, indicated by severe morphological alterations, a sign of elimination of the worms. Further investigation is being carried out to reveal the molecular mechanisms underlying the transfer of protection.

Structural changes of Schistosoma mansoni adult worms recovered from C57BL/6 mice treated with radiation-attenuated vaccine and/or praziquantel against infection

“…This result in comparing with that results obtained by Abdeen et al (2011). As RA vaccine generate high level of protection against subsequent challenge is not acceptable for use in human, reaching to vaccine depends on attenuated cercariae with indirect way as further target.…”

“…The data generated from our recent study (Abdeen et al 2011) suggest that high levels of antibodies were developed in the vaccinated rabbit sera after multiple exposures to UVattenuated cercariae of S. mansoni; this might explain a passive transfer of protection from the infection and elimination of the worms. Therefore, as a continuation of our recent study, the present study aims to compare vaccine efficacy of single or multiple vaccination strategy, subcurative dose (20 mg/kg) of PZQ, and a combination of single vaccination with subcurative dose of PZQ on the surface topography of adult S. mansoni.…”

Extracellular Vesicle Biogenesis in Helminths: More than One Route to the Surface?

“…Complementary transmission electron microscopy studies have confirmed that the blebs pinch directly from the tegumental surface and are released into the extracellular environment ( Figure 2) [55,[57][58][59]. It has been suggested that blebbing is an attempt by helminths to replenish tegument that has been lost or damaged due to drug action [60] or humoral immune challenge [61]. Given the abundance of pumps such as P-glycoprotein 1 in the parasite EV membrane [47] it is possible that blebs sequester anthelmintics before their release; thus, reducing their effective local concentration in the parasite tissues.…”

Transmission electron microscopic observations on ultrastructural alterations in Schistosoma mansoni adult worms recovered from C57BL/6 mice treated with radiation-attenuated vaccine and/or praziquantel in addition to passive immunization with normal and vaccinated rabbit sera against infection

“…The data generated from Abdeen et al (2012) has suggested that high levels of antibodies were developed in the vaccinated rabbit sera after multiple exposures to UV-attenuated cercariae of S. mansoni, explaining a passive transfer of protection from the infection and elimination of the worms. Reda et al (2012) compared vaccine efficacy of a single or multiple vaccination strategy, subcurative dose (20 mg/kg) of praziquantel (PZQ), and a combination of single vaccination with subcurative dose of PZQ on the surface topography of adult S. mansoni.…”