Structure, Immunoreactivity, and In Silico Epitope Determination of SmSPI <i>S. mansoni</i> Serpin for Immunodiagnostic Application

• Main Authors: Stefano De Benedetti, Flavio Di Pisa, Enrico Mario Alessandro Fassi, Marina Cretich, Angelo Musicò, Roberto Frigerio, Alessandro Mussida, Mauro Bombaci, Renata Grifantini, Giorgio Colombo, Martino Bolognesi, Romualdo Grande, Nadia Zanchetta, Maria Rita Gismondo, Davide Mileto, Alessandro Mancon, Louise Jane Gourlay
• Format: Article
• Language: English
• Published: MDPI AG 2021-04-01
• Series: Vaccines
• Subjects: Neglected Tropical Disease; circulating antigen; crystal structure; in silico epitope predictions; schistosomiasis; Serine protease inhibitor
• Online Access: https://www.mdpi.com/2076-393X/9/4/322

The human parasitic disease Schistosomiasis is caused by the <i>Schistosoma</i> trematode flatworm that infects freshwaters in tropical regions of the world, particularly in Sub-Saharan Africa, South America, and the Far-East. It has also been observed as an emerging disease in Europe, due to increased immigration. In addition to improved therapeutic strategies, it is imperative to develop novel, rapid, and sensitive diagnostic tests that can detect the <i>Schistosoma</i> parasite, allowing timely treatment. Present diagnosis is difficult and involves microscopy-based detection of Schistosoma eggs in the feces. In this context, we present the 3.22 Å resolution crystal structure of the circulating antigen Serine protease inhibitor from <i>S. mansoni</i> (SmSPI), and we describe it as a potential serodiagnostic marker. Moreover, we identify three potential immunoreactive epitopes using in silico-based epitope mapping methods. Here, we confirm effective immune sera reactivity of the recombinant antigen, suggesting the further investigation of the protein and/or its predicted epitopes as serodiagnostic Schistosomiasis biomarkers.