Destruction of Schistosoma mansoni sporocysts in Biomphalaria glabrata after phytochemical exposure.

Gabriela Friani,Marcela Figueiredo,Clélia Christina Mello-Silva,Patrícia S Gôlo,Ester Mota,Marta Júlia Faro,Samaly Souza,Valdir A Costa

doi:10.1590/0001-3765202220200620

Abstract

Schistosomiasis is a neglected tropical disease and affects over 200 million people worldwide. The snail Biomphalaria glabrata is one of the intermediate hosts of S. mansoni. The aim of this work was to verify the action of Euphorbia milii var. hislopii latex in the hemocytes profile and histopathology of B. glabrata infected by S. mansoni. Uninfected and infected snails were exposed to sublethal concentration of E. milii latex for 24 hours (1.0 mg/L). The survival rate was 88.5% for the uninfected snails and 66.6% for the infected and exposed snails. In the snails infected by S. mansoni, the exposure to E. milii latex promoted proliferation of hemocytes in the tentacles, mantle, digestive gland and kidney. In the digestive gland and the kidney, granulomatous reactions occurred around the sporocysts and caused their destruction. The number of circulating hemocytes from the group infected and exposed to E. milii latex was significantly higher than in the other groups. Three types of hemocytes were found: hyalinocytes, granulocytes and blast-like cells. We conclude that the E. milii latex influenced the cellular immune response of the susceptible B. glabrata strain to infection by S. mansoni, promoting the destruction of parasites.

Highlights

Biomphalaria glabrata is the main intermediate host of Schistosoma mansoni (Colley et al 2014, Lu et al 2018), the causative agent of Schistosomiasis mansoni, affecting around 200 million people worldwide and causing up to 260,000 deaths per year (WHO 2017, 2019)
It is worth mentioning that this is the first report on the effect of phytochemical products from E. milii could change the profile of hemocytes and influence the host’s immune response to the parasite
The E. milii latex exposure in B. glabrata infected stimulated hemocytes proliferation in the tissue after 24 hours and because of this was observed the presence of a granulomatous structure that caused the death of parasites

Summary

Introduction

Biomphalaria glabrata is the main intermediate host of Schistosoma mansoni (Colley et al 2014, Lu et al 2018), the causative agent of Schistosomiasis mansoni, affecting around 200 million people worldwide and causing up to 260,000 deaths per year (WHO 2017, 2019). In Brazil, intestinal schistosomiasis is largely associated with environmental variables and/or social determinants, infecting approximately 8 to 10 million people every year, while 25 million who live in endemic areas are at risk of infection (Scholte et al 2012). The interaction between S. mansoni and B. glabrata starts when the free-living forms (miracidia) infect the snails and become sporocysts, the longer-term asexual parasitic stage. The miracidia must be recognized as self, so that the carbohydrates present on their tegument bind to the lectins on the surface of the hemocytes or vice versa, and/ or free lectins in the hemolymph form bridges with the carbohydrates present on the surface. If the larvae are recognized as non-self, several mechanisms of the snail’s humoral and cellular responses work together to neutralize the non-self particles, especially pathogenic microorganisms (Zänker 2010, Pinaud et al 2019)

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