Characterisation of tetraspanins from Schistosoma haematobium and evaluation of their potential as novel diagnostic markers.

Gebeyaw G Mekonnen,Mark S Pearson,Matt Field,Alex Loukas,Francisca Mutapi,Javier Sotillo,Paul L A M Corstjens,Bemnet A Tedla,Luke Becker,Govert Van Dam,Abena S Amoah,Takafira Mduluza

doi:10.1371/journal.pntd.0010151

Abstract

Schistosoma haematobium is the leading cause of urogenital schistosomiasis and it is recognised as a class 1 carcinogen due to the robust association of infection with bladder cancer. In schistosomes, tetraspanins (TSPs) are abundantly present in different parasite proteomes and could be potential diagnostic candidates due to their accessibility to the host immune system. The large extracellular loops of six TSPs from the secretome (including the soluble excretory/secretory products, tegument and extracellular vesicles) of S. haematobium (Sh-TSP-2, Sh-TSP-4, Sh-TSP-5, Sh-TSP-6, Sh-TSP-18 and Sh-TSP-23) were expressed in a bacterial expression system and polyclonal antibodies were raised to the recombinant proteins to confirm the anatomical sites of expression within the parasite. Sh-TSP-2, and Sh-TSP-18 were identified on the tegument, whereas Sh-TSP-4, Sh-TSP-5, Sh-TSP-6 and Sh-TSP-23 were identified both on the tegument and internal tissues of adult parasites. The mRNAs encoding these TSPs were differentially expressed throughout all schistosome developmental stages tested. The potential diagnostic value of three of these Sh-TSPs was assessed using the urine of individuals (stratified by infection intensity) from an endemic area of Zimbabwe. The three Sh-TSPs were the targets of urine IgG responses in all cohorts, including individuals with very low levels of infection (those positive for circulating anodic antigen but negative for eggs by microscopy). This study provides new antigen candidates to immunologically diagnose S. haematobium infection, and the work presented here provides compelling evidence for the use of a biomarker signature to enhance the diagnostic capability of these tetraspanins.

Highlights

Schistosomiasis is a parasitic disease caused by blood dwelling trematodes from the genus Schistosoma and it is the second most important parasitic disease next to malaria in terms of social, economic and public health impact [1]
Schistosoma haematobium, the leading cause of urogenital schistosomiasis, affects millions of people worldwide. Infection with this parasite is associated with different clinical complications such as squamous cell carcinoma and genital malignancy in women
We have characterised six molecules belonging to the tetraspanin family of membrane proteins, providing details about their relative expression during parasite’s development and their localization in adult forms of S. haematobium

Summary

Introduction

Schistosomiasis is a parasitic disease caused by blood dwelling trematodes from the genus Schistosoma and it is the second most important parasitic disease next to malaria in terms of social, economic and public health impact [1]. Over 250 million people are affected and 700 million people live in areas at risk [2]. Pathogenesis associated with urogenital schistosomiasis is mainly caused by eggs trapped in tissues, in the bladder [9]. Some of the eggs penetrate the bladder wall and get excreted through urine; half of the produced eggs are carried away with the bloodstream and trapped in the tissues of different urogenital organs [10]. The eggs trapped in the capillary beds of the bladder stimulate an immune response [9], affecting the bladder wall, leading to general urinary dysfunction and progressing to obstructive renal pathology [11, 12]. Urogenital schistosomiasis may increase the risk of acquiring HIV infection [16]

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Conclusion