A recombinant protein containing influenza viral conserved epitopes and superantigen induces broad-spectrum protection.

Influenza pandemics pose public health threats annually for lacking vaccine that provides cross-protection against novel and emerging influenza viruses. Combining conserved antigens that induce cross-protective antibody responses with epitopes that activate cross-protective T cell responses might be an attractive strategy for developing a universal vaccine. In this study, we constructed a recombinant protein named NMHC that consists of influenza viral conserved epitopes and a superantigen fragment. NMHC promoted the maturation of bone marrow-derived dendritic cells and induced CD4+ T cells to differentiate into Th1, Th2, and Th17 subtypes. Mice vaccinated with NMHC produced high levels of immunoglobulins that cross-bound to HA fragments from six influenza virus subtypes with high antibody titers. Anti-NMHC serum showed potent hemagglutinin inhibition effects to highly divergent group 1 (H1 subtype) and group 2 (H3 subtype) influenza virus strains. Furthermore, purified anti-NMHC antibodies bound to multiple HAs with high affinities. NMHC vaccination effectively protected mice from infection and lung damage when exposed to two subtypes of H1N1 influenza virus. Moreover, NMHC vaccination elicited CD4+ and CD8+ T cell responses that cleared the virus from infected tissues and prevented virus spread. In conclusion, this study provides proof of concept that NMHC vaccination triggers B and T cell immune responses against multiple influenza virus infections. Therefore, NMHC might be a candidate universal broad-spectrum vaccine for the prevention and treatment of multiple influenza viruses.

Staphylococcal enterotoxin C2 stimulated the maturation of bone marrow derived dendritic cells via TLR-NFκB signaling pathway.

As a kind of superantigen, staphylococcal enterotoxin C2 (SEC2) is well known as a powerful immunomodulator. However, most previous studies about SEC2 focus on its T cell activating characters. But the direct effect of SEC2 on antigen-presenting cells (APCs) which are important for the T cell activation is not clearly. In this study, we investigated the effect of SEC2 on murine bone marrow-derived dendritic cells (BMDCs) which are known as the specialized professional APCs. Contrary to its effects on T cells, SEC2 could not induce proliferation or cytotoxicity to BMDCs even in high concentrations. While SEC2 could promote the mature of BMDCs with increased expression of co-stimulatory molecules on cell membrane such as CD80, CD86, and MHC II. The production of pro-inflammatory cytokines such as TNF-α, IFN-γ and IL-6 were also increased in BMDCs treated with SEC2. We also found that SEC2 enhanced the genes expression of pattern recognition receptors including toll-like receptors 2 (TLR2) and TLR4 in BMDCs, and up-regulated the key signal molecule MyD88 in both mRNA and protein levels. In addition, SEC2 also caused IκBα degradating and NFκB p65 translocating from the cytoplasm to the nucleus in BMDCs. The siRNAs for both TLR2 and TLR4, as well as NFκB specific inhibitor BAY 11-7085 could inhibit the co-stimulatory molecules expression and pro-inflammatory cytokines releasing induced by SEC2. Moreover, TLR2/4 specific siRNAs inhibited p65 and MyD88 upregulation induced by SEC2. In summary, all our results indicated that SEC2 could stimulate BMDCs maturation through TLR-NFκB signaling pathways.

Staphylococcal enterotoxin C2 as an adjuvant for rabies vaccine induces specific immune responses in mice.

Rabies vaccine administration is the most effective method to prevent the occurrence of rabies disease. However, administration of rabies vaccine without adjuvant always shows low efficiency. As a member of superantigen, staphylococcal enterotoxin C2 (SEC2) non-specifically activates T-cells at extremely low concentration. It enlightens us that SEC2 may be used as an adjuvant. We carried out the experiment that the mice received twice immunization with rabies vaccine in the presence or absence of SEC2 at 1-week interval. Serum and splenocytes from immunized mice were collected to measure the level of rabies-specific-IgG and the cell that secretes IFN-γ or IL-4. The promotion of antigen-specific splenocytes proliferation was also detected. Besides, a challenge test was performed to evaluate the protective efficiency of SEC2. It was shown that mice immunized with vaccine combined with SEC2 generated more specific anti-rabies-antibodies. The results for production of IFN-γ and IL-4, as well as the proliferation of splenocytes from immunized mice indicated SEC2 promoted the specific immune responses induced by rabies vaccine. Moreover, immunization of mice with vaccine combined with SEC2 provided efficient protection against the lethal rabies exposure. Taken together, our findings indicated that SEC2 can be served as an adjuvant for rabies vaccines.