Abstract
We characterized Schistosoma japonicum HSP40 (Sjp40) and HSP90α (Sjp90α) in this study. Western blot analysis revealed both are present in soluble egg antigens and egg secretory proteins, implicating them in triggering the host immune response after secretion from eggs into host tissues. These observations were confirmed by immunolocalization showing both HSPs are located in the Reynolds’ layer within mature eggs, suggesting they are secreted by miracidia and accumulate between the envelope and the eggshell. Both HSPs are present in the musculature and parenchyma of adult males and in the vitelline cells of females; only Sjp90α is present on the tegument of adults. Sjp40 was able to enhance the expression of macrophages, dendritic cells, and eosinophilic cells in mouse liver non-parenchymal cells, whereas rSjp90α only stimulated the expression of dendritic cells. T helper 1 (Th1), Th2, and Th17 responses were increased upon rSjp40 stimulation in vitro, but rSjp90 only stimulated an increased Th17 response. Sjp40 has an important role in reducing the expression of fibrogenic gene markers in hepatic stellate cells in vitro. Overall, these findings provide new information on HSPs in S. japonicum, improving our understanding of the pathological roles they play in their interaction with host immune cells.
Highlights
Schistosomiasis, caused by Schistosoma japonicum, is still a major public health problem that threatens many millions of people in the People’s Republic of China [1,2]
Multiple alignments showed that Schistosoma japonicum HSP40 (Sjp40) shares 69% amino acid sequence identity with Schistosoma mansoni HSP40 (Smp_302290), 64% amino acid sequence identity with S. haematobium, and 31% amino acid identity with Homo sapiens
For the Sjp40 structure, we found a protein homolog with an alignment length of 338 amino acids and corresponding PDB ID: 2bol.1.A, and this is shown in Figure 1a,b; the Sjp40 protein and this homolog showed 32.69% identity, with 88% coverage
Summary
Schistosomiasis, caused by Schistosoma japonicum, is still a major public health problem that threatens many millions of people in the People’s Republic of China [1,2]. The pathological mechanism of hepatic granuloma formation is a soluble egg antigen (SEA) and egg secretory protein (ESP)-induced complex immune response that results in the accumulation of macrophages, eosinophils, dendritic cells, CD4+ T cells and other immune cells [4]. Determining how these various immune cells are activated and recruited within the liver environment will provide new avenues to further understanding the process of immunopathology in schistosomiasis. One of the most abundant egg proteins from S. japonicum is the egg-derived heat shock protein 40 (HSP40, Sjp40), which is able to restrain the activation of hepatic stellate cells (HSCs) through the STAT3/p53/p21 pathway [9]. The peptides p6 (51–70), p25 (241–260), and p30 (291–310) derived from Sjp were able to inhibit allergic asthmatic reactions through inducing IFN-γ production [12], indicating a novel form of immune protection through helminth infection
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