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. 2019 Jan 25;15(1):38.
doi: 10.1186/s12917-019-1782-3.

Oral pre-administration of Purslane polysaccharides enhance immune responses to inactivated foot-and-mouth disease vaccine in mice

Rui Zhao  1 , Xiangyu Meng  2 , Guiyan Jia  3 , Yongzhong Yu  3 , Bocui Song  3
Affiliations

Oral pre-administration of Purslane polysaccharides enhance immune responses to inactivated foot-and-mouth disease vaccine in mice

Rui Zhao et al. BMC Vet Res. .

Abstract

Background: Foot-and-mouth disease (FMD) is one of the greatest disease threats to animal husbandry worldwide. Though various vaccines against foot-and-mouth disease virus (FMDV) have been developed, vaccine effectiveness is still not satisfactory. In this work, we studied the potential ability of Purslane polysaccharide (POL-P3b) as a nutrient food additive to enhance immune responses to FMD vaccination in mice.

Results: Our results demonstrated that oral administration of POL-P3b at mid- and high-doses significantly enhanced the FMDV-specific cellular and humoral immune responses in mice and increased the concentration of Ca2+ in lymphocytes. Importantly, POL-P3b could promote intestinal DC maturation and stimulate the secretion of intestinal SIgA in a dose-dependent manner. Moreover, the acute toxicity study showed that POL-P3b was non-toxic and safe in mice.

Conclusion: Our findings provided solid evidence that POL-P3b might be a novel immunostimulator and a boosting agent for increasing the efficacy of FMD vaccination, and the mechanism was related to stimulating the intestinal mucosal immune function that subsequently enhanced the efficacy of FMD vaccination through pre-administration of oral POL-P3b.

Keywords: Foot-and-mouth disease vaccine; Immune; Immunostimulator; Purslane polysaccharide.

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Conflict of interest statement

Ethics approval

All investigations were carried out in accordance with the “Guide to the Care and Use of Experimental Animals” and their experimental use was approved by the Animal Care and Use Committee of the Heilongjiang August First Land Reclamation University.

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

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Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Figures

Fig. 1
Fig. 1
Protection against FMDV in challenged mice. Mice (n = 20) were immunized twice with FMDV, and then challenged 21 days post first immunization with 105.0 TCID50/ 0.1 mL infectious FMDV O1C serotype by the i.p. route
Fig. 2
Fig. 2
Effects of POL-P3b on IgG and isotype in mice immunized with O type FMD inactivated vaccine. a Effects of POL-P3b on IgG. b Effects of POL-P3b on IgG isotypes. Data were expressed as mean ± SD (n = 10). ●P < 0.01, compared with control; ▲P < 0.05, ★P < 0.01, compared with FMDV
Fig. 3
Fig. 3
Effects of POL-P3b on cytokines in mice immunized with O type FMD inactivated vaccine. The concentrations of IFN-γ, IL-2, IL-4 and IL-6 were measured using commercially available ELISA-kits according to the manufacturer’s protocol. Data were expressed as mean ± SD (n = 10). ○P < 0.05, ●P < 0.01, compared with control; ▲P < 0.05, ★P < 0.01, compared with FMDV. The detection limits of these assays were 2 pg/mL (IL-2, IL-4 and IL-6) and 7 pg/mL (IFN-γ), respectively
Fig. 4
Fig. 4
Effects of POL-P3b on Ca2+ of lymphocyte in mice immunized with O type FMD inactivated vaccine. a Lymphocyte Ca2+ was analyzed using flow cytometry instrument. Data were also collected in FSC (forward scatter) and SSC (side scatter) and a total of 10,000 events were collected for each sample. A Control group; B FMDV group; C FMDV+ POL-P3b (L) group; D FMDV+ POL-P3b (M) group; E FMDV+ POL-P3b (H) group b The level of lymphocyte Ca2+ was indicated with fluorescence intensity (I). The computation formula is as follows: I = Log (x-mode) × 340. Data were expressed as mean ± S.D. (n = 10). ○P < 0.05, ●P < 0.01, compared with control; ▲P < 0.05, ★P < 0.01, compared with FMDV
Fig. 5
Fig. 5
Proportion of positive cells of phenotype expression of intestinal DCs in the immunized mice treated with POL-P3b a. Statistical bar graph of the protein expression b. The quantitated values represent the mean ± S.D.Compared with FMDV, *P < 0.05;**P < 0.01
Fig. 6
Fig. 6
Effects of POL-P3b on intestinal mucosa SIgA in mice immunized with O type FMD inactivated vaccine. ○P < 0.05, ●P < 0.01, compared with control; ▲P < 0.05, ★P < 0.01, compared with FMDV
Fig. 7
Fig. 7
Histology of hematoxylin- and eosin-stained sections of kidney and liver in mice treated by oral administration with POL-P3b (40 × 10). a kidney and b liver. Compared to mice in control group, mice treated with POL-P3b had normal kidney structure, and renal tubular and glomerular structures were clear. Mice treated with POL-P3b had normal liver structure, with clear hepatic vein in the middle and without visible degeneration, necrosis and inflammatory cells infiltration. Glomerular was indicated with the arrow; Central vein was indicated with the arrow. Scale bars, 100 μm
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