Adjuvant PIKA protects hepatoma cells from dengue virus infection by promoting a TBK-1-dependent innate immune response.

Our study presents a first investigation of the effect of the adjuvant PIKA on dengue virus (DENV) replication. PIKA pretreatment decreased the levels of DENV serotype 2 (DENV2) mRNA, protein and viral particles in the hepatoma cell line HepG2. Treatment with PIKA simultaneously with DENV2 infection, but not after infection, resulted in a protective effect. Significant induction of type I and type III interferons (IFNs), as well as interferon-stimulated genes was detected in PIKA-pretreated cells. Neutralization of IFN-ß partially restored the replication levels of DENV2 in PIKA-pretreated cells, suggesting that IFN-ß is one of the mediators involved in the antiviral action of PIKA. Additionally, blockade of TBK-1 signaling largely restored the IFN induction and viral suppression effects mediated by PIKA, further illustrating that PIKA plays its anti-DENV role by promoting innate immunity. These findings suggest that PIKA is an attractive agent to be used in the prevention of DENV diseases.

PIKA as an adjuvant enhances specific humoral and cellular immune responses following the vaccination of mice with HBsAg plus PIKA.

An adjuvant is usually used to enhance the immune response induced by vaccines. The choice of adjuvant or immune enhancer determines the effectiveness of the immune response. Currently, aluminium (Alum, a generic term for salts of aluminium) is the only FDA-approved adjuvant. Alum predominantly induces the differentiation of Th2 cells and thus mediates an antibody immune response. Therefore, there is an urgent need for new adjuvants that enhance not only humoral but also cellular immune responses. In the present study, we demonstrates that PIKA (a stabilized dsRNA) as an adjuvant directly induces the activation and the proliferation of both B and NK cells in vitro. Injection of PIKA into mice results in the production of cytokines in vivo. In addition, the study demonstrates that PIKA promotes the maturation of bone marrow-derived dendritic cells (BMDCs) including up-regulation of the co-stimulatory molecules CD80, CD86 and CD40, and the induction of cytokines such as IL-12p70, IL-12p40 and IL-6. Importantly, after immunization of mice with HBsAg plus PIKA, the presence of PIKA enhances the titers of HBsAg-specific IgG and HBsAg-specific IFN-gamma production. These results demonstrate that PIKA as an adjuvant can promote both humoral and cellular immune responses. These might have an implication in applying PIKA as an adjuvant to be used in the design and development of both therapeutic and preventive vaccines, and used in the clinical study.

Targeted Therapy of Hepatitis B Virus-Related Hepatocellular Carcinoma: Present and Future.

Cancer immunotherapy using a patient's own T cells redirected to recognize and kill tumor cells has achieved promising results in metastatic melanoma and leukemia. This technique involves harnessing a patient's T cells and then delivering a gene that encodes a new T cell receptor (TCR) or a chimeric antigen receptor (CAR) that allow the cells to recognize specific cancer antigens. The prospect of using engineered T cell therapy for persistent viral infections like hepatitis B virus (HBV) and their associated malignancies is promising. We recently tested in a first-in-man clinical trial, the ability of HBV-specific TCR-redirected T cells to target HBsAg-productive hepatocellular carcinoma (HCC) and demonstrated that these redirected T cells recognized HCC cells with HBV-DNA integration [1] We discuss here the possibility to use HBV-specific TCR-redirected T cells targeting hepatitis B viral antigens as a tumor specific antigen in patients with HBV-related HCC, and the potential challenges facing the development of this new immunotherapeutic strategy.

A novel rabies vaccine based-on toll-like receptor 3 (TLR3) agonist PIKA adjuvant exhibiting excellent safety and efficacy in animal studies.

Vaccination alone is not sufficiently effective to protect human from post-exposure rabies virus infection due to delayed generation of rabies virus neutralizing antibodies and weak cellular immunity. Therefore, it is vital to develop safer and more efficacious vaccine against rabies. PIKA, a stabilized chemical analog of double-stranded RNA that interacts with TLR3, was employed as adjuvant of rabies vaccine. The efficacy and safety of PIKA rabies vaccine were evaluated. The results showed that PIKA rabies vaccine enhanced both humoral and cellular immunity. After viral challenge, PIKA rabies vaccine protected 70-80% of animals, while the survival rate of non-adjuvant vaccine group (control) was 20-30%. According to the results of toxicity tests, PIKA and PIKA rabies vaccine are shown to be well tolerated in mice. Thus, this study indicates that PIKA rabies vaccine is an effective and safe vaccine which has the potential to develop next-generation rabies vaccine and encourage the start of clinical studies.

Ineffectiveness of rabies vaccination alone for post-exposure protection against rabies infection in animal models.

Most reported vaccination failures among rabies-exposed patients were due to fail to timely co-administer rabies immunoglobulin (RIG). Considering that such protection failure might be caused by low antigen titers in the vaccine, scientists improved antigen titers to 4.0 IU or even higher, yet the failure remained. Therefore, it becomes vital to develop more efficacious vaccine against rabies. In our evaluation of a novel PIKA rabies vaccine, we used multiple animal models (beagles, golden hamsters and Kunming mice) to mimic post-exposure scenarios. All animals were challenged with wild-type rabies virus, followed by vaccination with either rabies vaccines commercially available or PIKA rabies vaccines. As 100% of animals survived after administration of traditional rabies vaccines and rabies immunoglobulin, 80% of animals survived with rabies immunoglobulin alone. Strikingly, animals receiving traditional rabies vaccines alone showed extremely low survival rates, indicating insignificant benefit for exposed animals (p > 0.05, compared to unvaccinated control groups). To the contrary, 40-80% of animals receiving the experimental PIKA rabies vaccines were protected (p < 0.05, compared to unvaccinated control groups). If the above results are fully confirmed, we may conclude that currently as high as 99% of post-exposure patients who are seeking protection against rabies, but only receiving rabies vaccination, could be meaningless.