Evaluation and characteristics of immunological adjuvant activity of purified fraction of Albizia julibrissin saponins

ABSTRACT

Purpose: The purified fraction of Albizia julibrissin saponins (AJSAF) was evaluated and characterized for the adjuvant activity on porcine reproductive and respiratory syndrome virus (PRRSV) vaccine.

Methods: The effects of AJSAF on serum PRRSV N protein-specific antibody titers, splenocyte proliferation, natural killer (NK) cell activity, mRNA expression of cytokines and transcription factors, secretion of cytokines, T cells response in splenocytes, as well as delayed type hypersensitivity (DTH) in the mice immunized PRRSV vaccine were determined by ELISA, MTT assay, flow cytometry and quantitative real-time PCR (qRT-PCR).

Results: AJSAF not only significantly enhanced the serum PRRSV N protein-specific IgG, IgG1, IgG2a and IgG2b antibody titers in the mice immunized with PRRSV CH-1R modified live vaccine (CH-1R MLV), inactivated vaccine (CH-1R IAV), and highly pathogenic JXA1-R modified live vaccine (JXA1-R MLV), but promoted the concanavalin A (Con A)-, lipopolysaccharide (LPS)- and PRRSV N protein-stimulated splenocyte proliferation, the activities of NK cells and delayed type hypersensitivity (DTH) in the mice immunized CH-1R MLV. AJSAF also remarkably induced the production of both Th1 (IFN-γ) and Th2 (IL-10) cytokines, and up-regulated the mRNA expression levels of Th1 cytokines (IFN-γ and IL-2) and transcription factors (T-bet and STAT4) as well as Th2 cytokines (IL-4 and IL-10) and transcription factors (GATA-3 and STAT6) in splenocytes from the CH-1R MLV-immunized mice. Furthermore, AJSAF markedly increased the frequencies of PRRSV N protein-specific Th1 (INF-γ⁺ and IL-2⁺) and Th2 (IL-4+ and IL-10⁺) CD4 T cells as well as Tc1 (INF-γ⁺ and IL-2⁺) and Tc2 (IL-4⁺ and IL-10⁺) CD8 T cells in splenocytes from the CH-1R MLV-immunized mice.

Conclusions: Our results demonstrated that AJSAF had a potential to enhance and improve immune responses and elicit both Th1/Th2 and Tc1/Tc2 response to PRRSV vaccine, and that AJSAF would be a promising adjuvant candidate for PRRSV vaccine.

KEYWORDS:

• Adjuvant
• Albizia julibrissin saponin
• immune response
• PRRSV vaccine
• purified active fraction
• T cells response

Author’s Contribution

ZBN, TYH, XYG, MHS, and HXS conducted all experiments and collected the data. ZBN analyzed the data and wrote the manuscript. HXS designed the study and revised the manuscript. All authors read and approved the final manuscript.

Disclosure Statement

The authors report no conflicts of interest.

Supplementary material

Supplemental data for this article can be accessed here.

Additional information

Funding

This work was supported by the National Key R&D Program of China under [Grant no. 2017YFD0501505]; the National Natural Science Foundation of China under [Grant nos. 31272597, 31472229 and 3172783]; and the Zhejiang Provincial Natural Science Foundation of China under [Grant no. LZ13C180001].