Abstract
The aim of this study was to investigate the biological characteristics and functions of a Trichinella spiralis serine proteinase (TsSerp) during larval invasion and development in the host. The full-length TsSerp cDNA sequence was cloned and expressed in Escherichia coli BL21. The results of RT-PCR, IFA and western blotting analyses showed that TsSerp was a secretory protein that was highly expressed at the T. spiralis intestinal infective larva and muscle larva stages and primarily located at the cuticle, stichosome and intrauterine embryos of the parasite. rTsSerp promoted the larval invasion of intestinal epithelial cells (IECs) and the enteric mucosa, whereas an anti-rTsSerp antibody impeded larval invasion; the promotion and obstruction roles were dose-dependently related to rTsSerp and the anti-rTsSerp antibodies, respectively. Vaccination of mice with rTsSerp elicited a remarkable humoral immune response (high levels of serum IgG, IgG1/IgG2a, IgE and IgM), and it also triggered both systemic (spleen) and local intestinal mucosal mesenteric lymph node (MLN) cellular immune responses, as demonstrated by a significant elevation in Th1 cytokines (IFN-γ) and Th2 cytokines (IL-4) after the spleen and MLN cells from vaccinated mice were stimulated with rTsSerp. Anti-TsSerp antibodies participated in the killing and destruction of newborn larvae via ADCC. The mice vaccinated with rTsSerp exhibited a 48.7% reduction in intestinal adult worms and a 52.5% reduction in muscle larvae. These results indicated that TsSerp participates in T. spiralis invasion and development in the host and might be considered a potential candidate target antigen to develop oral polyvalent preventive vaccines against Trichinella infection.
Highlights
The genus Trichinella, including 10 species and 3 genotypes, is distributed in more than 150 domestic and wild mammals, and some species of the genus may cause the meat-borne zoonosis trichinellosis [1]
Our results demonstrated that rTsSerp vaccination triggered mixed Th1/Th2 responses on the basis of specific IgG subclass responses and cytokine generation, suggesting that subcutaneous vaccination with rTsSerp triggered both systemic and local intestinal mucosal (MLN) cellular immune responses
Previous studies have shown that Trichuris muris serine proteinase can disrupt the integrity of intestinal epithelial cell membranes, which is due to hydrolysis of the mucus barrier of the host intestinal surface [58]
Summary
The genus Trichinella, including 10 species and 3 genotypes, is distributed in more than 150 domestic and wild mammals, and some species of the genus may cause the meat-borne zoonosis trichinellosis [1]. From 2004 to 2009, 12 trichinellosis outbreaks due Following ingestion, encapsulated muscle larvae (MLs) of T. spiralis are liberated from their collagen capsules. In the process of the T. spiralis lifecycle, the excretory/secretory (ES) antigens of MLs and IILs are first exposed to host intestinal epithelium cells (IECs), and they might exert an important role in larval invasion and trigger the early immune response [11]. Serine proteases are a family of proteolytic enzymes that have multiple biological roles during parasite infection, and they are involved in worm invasion, migration and proteolysis of the host’s various tissues [15, 16]. Serine proteases might participate in T. spiralis larval invasion of IECs [17], and they might be important antigenic molecular targets for anti-Trichinella vaccines [18, 19]
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