Background: Survivin is a member of the inhibitor-of-apoptosis (IAP) family which is widely expressed by many different cancers. Overexpression of survivin is associated with drug resistance in cancer cells, and reduced patient survival after chemotherapy and radiotherapy. Agents that antagonize the function of survivin hold promise for treating many forms of cancer. The purpose of this study was to investigate whether a cell-permeable dominant-negative survivin protein would demonstrate bioactivity against prostate and cervical cancer cells grown in three dimensional culture. Results: A dominant-negative survivin (C84A) protein fused to the cell penetrating peptide poly-arginine (R9) was expressed in E. coli and purified by affinity chromatography. Western blot analysis revealed that dNSurR9-C84A penetrated into 3D-cultured HeLa and DU145 cancer cells, and a cell viability assay revealed it induced cancer cell death. It increased the activities of caspase-9 and caspase-3, and rendered DU145 cells sensitive to TNF-α via by a mechanism involving activation of caspase-8. Conclusions: The results demonstrate that antagonism of survivin function triggers the apoptosis of prostate and cervical cancer cells grown in 3D culture. It renders cancer cells sensitive to the proapoptotic affects of TNF-α, suggesting that survivin blocks the extrinsic pathway of apoptosis. Combination of the biologically active dNSurR9-C84A protein or other survivin antagonists with TNF-α therapy warrants consideration as an approach to cancer therapy.

Streptococcus suis (S. suis) causes arthritis, meningitis, septicemia, and sudden death in pigs and is also an zoonotic agent for humans. The present study demonstrated that immunization with recombinant Sao-L (surface antigen one-L, rSao-L) protein from a strain of S. suis serotype 2 in pigs was able to increase cross-serotype protection against S. suis serotype 1 and 2 challenge. Since weaning piglets are more susceptible to S. suis infections due to the stresses associated with weaning, prepartum immunization in sows may convey passive immunity to piglets and provide protection. Pregnant sows were immunized with a vaccine containing inactivated S. suis serotype 2 plus rSao as the antigens. Blood samples were collected from their piglets after birth for analysis of antigen-specific antibody titers and levels of various cytokines. Results demonstrated that the titers of S. suis and rSao-specific antibodies were significantly (p < 0.05) higher in the vaccinated piglets in comparison with that of piglets in the control group. The serum levels of interferon (IFN)-γ, interleukin (IL)-4, IL-6, and IL-12 were significantly (p < 0.05) increased in piglets born from vaccinated sows when compared to piglets from unvaccinated sows. In addition, piglets were challenged by heterologous and homologous S. suis. All piglets from unvaccinated sows developed severe symptoms of bacteremia, fever, anorexia, depression, and arthritis. On the other hand, piglets from vaccinated sows had significantly (p < 0.05) reduced clinical symptoms and lesion score (by 75 and 81%). Our results revealed that immunizing pregnant sows with the vaccine containing inactivated S. suis bacterin plus rSao as the antigens is able to enhance passive immunity against heterologous and homologous S. suis challenge in their piglets.

Flagellin stimulates Toll-like receptor 5 (TLR5), triggering both innate and adaptive immune responses, making it a potential vaccine adjuvant. On mucosal surfaces, flagellin induces a strong release of cytokines, chemokines, and immunoglobulins. When used in its free monomeric form, flagellin has been shown to enhance immune responses when combined with vaccine antigens. Further research demonstrated that genetically linking flagellin to the antigen provides a more consistent immune boost. However, the bulky structure of flagellin presents challenges in designing the antigen-adjuvant construct, leading to ongoing research to determine the minimal flagellin domain necessary for its adjuvant effect. Early findings suggest that only the D0 and D1 domains are required for immune enhancement. Functional analysis revealed that the TLR5-binding region is located in the D1 domain, while TLR5 dimerization and signaling require the presence of D0. Further reductions in the size of the D0 and D1 domains may be possible as deeper studies aim to identify the key residues responsible for TLR5 activation and immune enhancement. Additionally, flagellin is being tested as a hapten carrier alongside its established adjuvant role. Recently, significant advancements in flagellin application have been observed as it progresses through clinical studies as an adjuvant, anti-radiation, and anti-cancer agent.

Flagellin from bacteria elicits a proinflammatory immune response and may act as a vaccine adjuvant. In this study, we evaluated the adjuvant effect of the N-terminus of flagellin (residues 1–99) when linked to an antigen (a truncated, conserved domain of lipoprotein E of Pasteurella multocida). Immunization of chickens with the antigen-adjuvant chimeric protein showed that the N-terminus of flagellin accelerated the antibody response and enhanced the cellular immunity (CD8⁺ T cell expansion). Stimulation of peripheral blood mononuclear cells from vaccinated chickens showed both T_H1 (IFN-γ and IL-12) and T_H2 (IL-4)-type cytokine gene expressions. In a challenge test, the N-terminus of flagellin increased the survival rate to 75%, compared to 25% in the antigen-only group. In conclusion, our study found that the N-terminus of flagellin can increase the immune response and enhance vaccine protection.

In this study, we sought to develop a subunit vaccine against the increasingly prevalent Duck hepatitis A virus serotype 3 (DHAV-3). The VP1 protein of DHAV-3 and a truncated version containing the C-terminal region of VP1, termed VP1-C, were expressed recombinantly in Escherichia coli as vaccine antigens. For enhanced immune response, a truncated version of flagellin, nFliC, was included as vaccine adjuvant. Ducklings were vaccinated once for immune response analysis and challenge test. Results showed that VP1-C elicited a higher level of virus-specific antibody response and neutralization titer than VP1. The addition of nFliC further enhanced the antibody response. In terms of cellular immune response, the VP1-C + nFliC vaccine elicited the highest level of T cell proliferation among the vaccine formulations tested. Examination of the cytokine expression profile showed that peripheral blood mononuclear cells from the VP1-C + nFliC vaccine group expressed the highest levels of pro-inflammatory (IL-6) and TH-1 type (IL-12 and IFN-γ) cytokines. Finally, in a DHAV-3 challenge test, the VP1-C + nFliC vaccine provided a 75% protection rate (n = 8), in contrast to 25% for the VP1 vaccine. In conclusion, E. coli-expressed VP1-C has been shown to be a promising antigen when combined with nFliC and may be further developed as a single-dose subunit vaccine against DHAV-3.