Diagnostic Markers for Schistosome-Mediated Liver Disease

Chronic schistosomiasis presents with either a moderate or a severe form, termed intestinal (INT) or hepatosplenic (HS) schistosomiasis, respectively. The Schistosoma mansoni-associated hepatomegaly is estimated in 8.5 million people and ultimately results from liver granulomas induced by trapped parasitic eggs. The CBA/J mouse model replicates these two human disease forms and was used to understand the progressive pathology that leads to HS and to identify potential biomarkers. In this model 20% of infected mice spontaneously develop hypersplenomegaly syndrome (HSS) by 20 weeks of infection while the remaining 80% develop moderate splenomegaly syndrome (MSS). Using this model, we compared the liver protein patterns of control mice and mice infected for 6, 8, 12, or 20 (MSS and HSS) weeks. Two-dimensional differential in gel electrophoresis (2D-DIGE) was used to identify protein pattern variations and protein spots were identified using matrix adsorption laser desorption ionisation-time of flight (MALDI-TOF) mass spectrometry. In the first experiment, we found 124 protein spot unique changes for MSS and HSS compared to control mice of which 80 were identified and 35 changes were specific for HSS. In the second experiment, comparison between various time points with control mice revealed 76 significant protein spot changes of which 44 were identified using MALDI-TOF mass spectrometry. Importantly, we found that the abundance of liver keratin D, transferrin isoforms, collagen isoforms, hydroxyproline and Schistosoma mansoni-phosphoenolpyruvate carboxykinase increased while epoxide hydrolase isoforms, peroxiredoxin 6 and major urinary protein (MUP) isoforms decreased significantly with infection. To verify the changes in the liver 2D-DIGE analysis, candidate liver protein markers were measured in mouse serum using targeted biochemical assays. The mouse serum analysis showed MUP levels were decreased, while transferrin, connective tissue growth factor (CTGF), keratin D, hydroxyproline were increased in HSS mice compared to control mice or MSS mice supporting the liver 2D-DIGE analysis. Using targeted assays, serum samples from INT and HS patients were tested for the candidate liver protein markers: keratin D, CTGF, hydroxyproline and transferrin. The human serum analysis showed keratin D levels increased for HS compared to INT and normal sera. The CTGF levels were high in INT compared to HS and normal sera, while transferrin remained unchanged in INT and HS similar to normal sera. Additionally, in severe HS disease, serum hydroxyproline emerged as a strong indicator of fibrosis. We believe that these findings will have direct value in the development of diagnostic tools for early detection of hepatosplenic schistosomiasis in humans.