Oral immunization of mice with recombinant Lactobacillus plantarum expressing a Trichinella spiralis galectin induces an immune protection against larval challenge

Abstract

Background Trichinella spiralis is an important foodborne parasite that presents a severe threat to food safety. The development of an anti-Trichinella vaccine is an important step towards controlling Trichinella infection in food animals and thus ensure meat safety. Trichinella spiralis galectin (Tsgal) is a novel protein that has been identified on the surface of this nematode. Recombinant Tsgal (rTsgal) was found to participate in larval invasion of intestinal epithelium cells (IECs), whereas anti-rTsgal antibodies impeded the invasion. Methods The rTsgal/pSIP409- pgsA′ plasmid was constructed and transferred into Lactobacillus plantarum strain NC8, following which the in vitro biological properties of rTsgal/NC8 were determined. Five groups of mice were orally immunized three times, with a 2-week interval between immunizations, with recombinant NC8-Tsgal, recombinant NC8-Tsgal + α-lactose, empty NC8, α-lactose only or phosphate-buffered saline (PBS), respectively. The vaccinated mice were infected orally with T. spiralis larvae 2 weeks following the last vaccination. Systemic and intestinal local mucosal immune responses and protection were also assessed, as were pathological changes in murine intestine and skeletal muscle. Results rTsgal was expressed on the surface of NC8-Tsgal. Oral immunization of mice with rTsgal vaccine induced specific forms of serum immunoglobulin G (IgG), namely IgG1/IgG2a, as well as IgA and gut mucosal secretion IgA (sIgA). The levels of interferon gamma and interleukin-4 secreted by cells of the spleen, mesenteric lymph nodes, Peyer's patches and intestinal lamina propria were significantly elevated at 2–6 weeks after immunization, and continued to rise following challenge. Immunization of mice with the oral rTsgal vaccine produced a significant immune protection against T. spiralis challenge, as demonstrated by a 57.28% reduction in the intestinal adult worm burden and a 53.30% reduction in muscle larval burden, compared to the PBS control group. Immunization with oral rTsgal vaccine also ameliorated intestinal inflammation, as demonstrated by a distinct reduction in the number of gut epithelial goblet cells and mucin 2 expression level in T. spiralis-infected mice. Oral administration of lactose alone also reduced adult worm and larval burdens and relieved partially inflammation of intestine and muscles. Conclusions Immunization with oral rTsgal vaccine triggered an obvious gut local mucosal sIgA response and specific systemic Th1/Th2 immune response, as well as an evident protective immunity against T. spiralis challenge. Oral rTsgal vaccine provided a prospective approach for control of T. spiralis infection. Graphical Abstract

Binding of Trichinella spiralis C-type lectin with syndecan-1 on intestinal epithelial cells mediates larval invasion of intestinal epithelium

“…Each group of mice was injected subcutaneously with 20 µg rTsCTL or GST tag protein emulsified with complete Freund’s adjuvant, and followed by two boost immunizations with 20 µg rTsCTL or GST tag emulsified with incomplete Freund’s adjuvant at a 2-week-interval [ 32 ]. At 2 weeks after the third injection, the tail blood from all immunized mice was recovered to prepare anti-rTsCTL serum or anti-GST serum; pre-immune serum was also obtained to use as a negative serum control [ 33 , 34 ].…”

A novel trypsin of Trichinella spiralis mediates larval invasion of gut epithelium via binding to PAR2 and activating ERK1/2 pathway

“…Goat anti-mouse IgG-Alexa Fluor 488 conjugate (1:100; Servicebio, Wuhan China) was used as the secondary antibody. After washing again, the cells were examined under fluorescence microscopy and confocal microscopy (Olympus, Japan) [4].…”

“…Finally, the color of the strips was developed using an enhanced chemiluminescence kit (CWBIO, Beijing, China). The results for the above proteins were normalized using GAPDH as a loading control [4,18].…”

“…Trichinella infection is not only a major public health issue but also a risk to meat safety. Nevertheless, it is difficult to eliminate Trichinella infection in animals because Trichinella has a diverse range of natural hosts and commercial veterinary anti-Trichinella vaccines are no available up to now [4]. Therefore, novel Trichinella invasion-related proteins with strong immunogenicity need to be identified, and preventive anti-Trichinella vaccines with high protection are necessary to be developed to eliminate Trichinella infection in food animals [5,6].…”

How to train your myeloid cells: a way forward for helminth vaccines?

“…Similarly, vaccination against O. volvulus ASP-1 has been shown to induce a dominant interferon-gamma (IFN-γ) response, which is likely linked to the abundance of activated NK cells and neutrophils ( 189 ). Finally, a recent vaccine against T. spiralis based on a recombinant galectin was shown to be protective and cause high levels of intestinal histamine release ( 190 ).…”