Lentinan improved the efficacy of vaccine against Trichinella spiralis in an NLRP3 dependent manner

Abstract

There is an urgent need for the development of new, improved vaccine adjuvants against T. spiralis infection. Polysaccharides are effective, safe, and biodegradable as adjuvant. In our study, we first observed the protective efficacy of lentinan as adjuvant against helminth T. spiralis infection. Recombinant T. spiralis Serpin (rTs-Serpin) immunoscreened from a cDNA library of T. spiralis, as a vaccine, protect host against Trichinella infection. The reduction rate of helminth burden of rTs-Serpin+lentinan-immunized mice was significantly increased compared with rTs-Serpin+FCA-immunized mice. rTs-Serpin+lentinan induced IgG1-dominant immune response and higher levels of IFN-γ and IL-4. rTs-Serpin+lentinan displayed a lower reduction rate of parasite burden in NLRP3-/mice than that in WT mice and lower level of IgG1 than that in WT mice. The level of IL-4, but not IFN-γ, from NLRP3-/mice immunized by rTs-Serpin+lentinan was significantly lower than that from WT mice, suggesting that NLRP3 is associated with rTs-Serpin+lentinan-triggering Th2 protective immunity against T. spiralis infection. In summary, we revealed that lentinan was a novel adjuvant against T. spiralis infection via NLRP3. NLRP3 therefore represents an important target for adjuvant discovery and the control of T. spiralis infection.

Adjuvanticity of β -Glucan for Vaccine Against Trichinella spiralis

“…The T. spiralis isolate (ISS534), genotyped and proved by OIE Collaborating Center on Foodborne Parasites in Asian-Pacific Region, was preserved by serial passages in Wistar rats as described previously (Jin et al, 2020b). Briefly, Wistar rats were orally infected with 3000 infective larvae, and T. spiralis muscle larvae were recovered at 35 days post infection (dpi) via artificial digestion with pepsin-HCl (1% pepsin and 1% HCl at 37 • C for 2 h).…”

“…Recombinant Ts-Serpin (rTs-Serpin) was expressed in Escherichia coli (BL21) and purified as previously described (Xu et al, 2017;Jin et al, 2020b). The contaminated endotoxin was effectively removed by ToxOut High Capacity Endotoxin Removal Kit (Biovision, United States), approximately equivalent to 20 pg/mg endotoxin in rTs-Serpin (Jin et al, 2020b).…”

“…Blood was collected from mice at 2, 4, and 6 wpv. The titers of anti-rTs-Serpin IgG, IgG1, IgG2a subclasses, and IgE were measured using an indirect enzymelinked immunosorbent assay (ELISA) as described previously (Jin et al, 2020b).…”

“…Cytokine production from splenocyte culture supernatants was tested as described previously (Jin et al, 2020b). Briefly, 1 week after the final immunization, CD4 + T cells in spleens derived from mice were purified using anti-CD4 magnetic beads (Miltenyi Biotec).…”

“…More importantly, many natural polysaccharides are safe with no tissue deposition in the host (Sun et al, 2018). Previously, we showed that lentinan derived from mushrooms can improve the protective immunity of the vaccine on T. spiralis infection (Jin et al, 2020b). β-glucans is also present in mushrooms, yeast, oats, barley, seaweed and many other organism species, but does not exist in mammals.…”