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Lycium barbarum polysaccharides (LBP) have been shown to play a variety of immune-modulatory functions which include activation of T and B cells. Follicular helper T (Tfh) cells are now recognized as a subset of helper T cells which regulate the multiple stages of B cell maturation and function. In our current study, we found that LBP were able to activate CXCR5+PD-1+ Tfh cells and induce IL-21 secretion. At the same time LBP also promoted the formation of germinal centers (GC) and production of GL-7+B220+GC B cells. LBP as an adjuvant could increase generation of rAd5VP1-induced Tfh cells. Our results indicate that LBP might enhance T cell-dependent Ab responses by acting as an adjuvant for the generation of Tfh cells. Future vaccine designs might therefore be targeted to induce strong antigen-specific Tfh responses in order to boost its protective effects.

IFN-α exhibits either direct antiviral effects or distinct immunomodulatory properties, which was identified as a 'natural immune adjuvant' for both the innate and the adaptive immune responses. Here we have investigated the effects of IFN-α as an adjuvant on the generation of T follicular helper (Tfh) cells and antigen-specific antibody responses. The data showed that adenoviral vectors co-expressing FMDV VP1 proteins and porcine IFN-α potently enhanced the generation of Tfh cells, the secretion of IL-21 protein and the expression of Bcl-6 mRNA, compared with adenoviral vectors sole expressing VP1 alone. Additionally, IFN-α substantial increased the number of germinal-center (GC) B cells and formation of GCs. Furthermore, IFN-α enhanced the antibody response, as shown by increased production of all IgG and subclasses of IgG1 and IgG2a. Thus, our results revealed the potent adjuvant activity of IFN-α which enhanced the generation of Tfh cells and regulated the humoral immunity by promoting germinal-center reactions and antibody responses.

Adjuvants play an important role in the formulation of effective and appropriate vaccines. A series of synthetic bursin and bursin-like peptides was heterologously expressed in Escherichia coli. The use of bursin as an adjuvant enhanced the specific immune responses of mice immunized with a recombinant Japanese encephalitis virus E-binding domain (JEV E-BD) fusion protein. The effect was determined in the form of protective anti-JEV E titers, antibodies (IgG1 and IgG2a), spleen cell lymphocyte proliferation, the levels of interferon-γ and interleukin-4 cytokines, and the T-lymphocyte sub-type composition. The IgG2a titer and interferon-γ level suggested that the E-BD protein potentiates the Th1 immune response. These responses were changed when the immunogen was combined with one of the synthetic peptides as adjuvant. JEV-neutralization assay results show that the presence of bursin significantly enhance the JEV-neutralizing titer. We conclude that bursin as an adjuvant is a potent enhancer of immune response in mice immunized with the JEV subunit vaccine, and represents a promising adjuvant for vaccination.

Mycobacterium tuberculosis heat shock protein70 (HSP70) is a major antigen with both chaperone and cytokine functions. It has been used as an adjuvant to induce or potentiate humoral and cellular immunity, both in the form of a mixture with peptide antigens, and as a fusion protein. We have evaluated the effects of HSP70 on foot and mouth virus (FMDV) subunit vaccines. FMDV VP1, and a synthetic multi-epitope FMDV (EG), and VP1-HSP70 and EG-HSP70 fusion proteins were all heterologously expressed in the yeast Pichia pastoris , and used as antigen in mice . The recombinant VP1 and EG alone was able to induce both humoral and marginal cell-mediated immune responses, while the HSP70 fusions markedly enhanced both the humoral and cell-mediated immune responses. The most prominent immune responses arose from vaccination with the EG-HSP70 fusion product. Both fusion protein-induced Th1-like cytokine (IFN-γ) and Th2-like cytokine (IL-4) were identified.

Vp1 gene of O type foot-and-mouth diseases virus and M. tuberculosis HSP70 were expressed in methylotrophic yeast Pichia pastoris expression system. The results of cellular immune responses and humoral immune response were examined after BALB/c mice were immunized with fusion protein expressed in methylotrophic yeast Pichia pastoris. The genes was cloned into the vector pPICZalpha-A by routine molecular technique. The plasmid fusion (pPICZalphaA-vp1-HSP70) was created that HSP70 located downstream of VP1 gene of O type foot-and-mouth disease virus. Vp1 was expressed by fusing to the amino terminus of M. tuberculosis hsp70 in yeast Pichia pastoris. The recombined fusion plasmid was transformed into methylotrophic yeast Pichia pastoris X-33 by electrophoration. The recombinant transformants were selected by Zeocin and induced by the addition of methanol every 24h. The expressived product analyzed by SDS-PAGE and Western blotting. The result indicated that the fusion protein(vp1-HSP70) has specific antigenicity. Mice were inoculated transcutaneous three times at a two-weeks interval with fusion protein, PBS and conventional inactivated vaccines. To evaluate the prophylaxtic efficacy of fusion protein, Titers of antibodies was detected by ELISA and proliferation of lymphocytes were determined by MTT. The results indicated that fusion protein could elicit specific humoral immune and cellular immune responses. Compared with conventional inactivated vaccines, fusion protein elicited slightly lower FMDV antibody level but stronger T cell proliferation.