A novel TLR7 agonist as adjuvant to stimulate high quality HBsAg-specific immune responses in an HBV mouse model

Abstract

Background: The global burden of hepatitis B virus (HBV) infection in terms of morbidity and mortality is immense. Novel treatments that can induce a protective immune response are urgently needed to effectively control the HBV epidemic and eventually eradicate chronic HBV infection. Methods:We designed and evaluated an HBV therapeutic vaccine consisting of a novel Toll-like receptor 7 (TLR7) agonist T7-EA, an Alum adjuvant and a recombinant HBsAg protein. We used RNA-seq, ELISA and hTLR7/8 reporting assays to characterize T7-EA in vitro and real-time PCR to evaluate the tissue-retention characteristics in vivo. To evaluate the adjuvant potential, we administrated T7-EA intraperitoneally in a formulation with an Alum adjuvant and HBsAg in normal and HBV mice, then, we evaluated the HBsAg-specific immune responses by ELISA and Elispot assays.Results: T7-EA acted as an hTLR7-specific agonist and induced a similar gene expression pattern as an unmodified TLR7 ligand when Raw 264.7 cells were exposed to T7-EA; however, T7-EA was more potent than the unmodified TLR7 ligand. In vivo studies showed that T7-EA had tissue-retaining activity with stimulating local cytokine and chemokine expression for up to 7 days. T7-EA could induce Th1-type immune responses, as evidenced by an increased HBsAgspecific IgG2a titer and a T-cell response in normal mice compared to mice received traditional Alum-adjuvant HBV vaccine. Importantly, T7-EA could break immune tolerance and induce persistent HBsAg-specific antibody and T-cell responses in an HBV mouse model. Conclusions:T7-EA might be a candidate adjuvant in a prophylactic and therapeutic HBV vaccine.

TLR Agonists as Mediators of Trained Immunity: Mechanistic Insight and Immunotherapeutic Potential to Combat Infection

“…Additionally, several TLR7 agonists have been shown to improve immunity of hepatitis B-infected hosts and are implicated as potential HBV vaccine adjuvants. When administered together with an alum adjuvant and recombinant hepatitis B surface antigen (HBsAg) protein, the novel TLR7 agonist T7-EA induced HBsAg-specific antibody and restored T-cell responses in a murine model ( 133 ). Similar improvement of HBsAg-specific T-cell function was observed by immunizing HBV-transgenic mice with a TLR7/TLR8 agonist (CL097)-conjugated HBV protein ( 134 ).…”

Toward a new era of hepatitis B virus therapeutics: The pursuit of a functional cure

“…Interestingly, a novel TLR-7 agonist (T7-EA) has been developed as a component of a therapeutic vaccine that is under investigation. T7-EA has demonstrated the ability to reverse immune tolerance to the HBV by inducing HBsAg-specific antibody production and Th1-type immune responses in healthy and HBV-infected mice[ 118 ].…”

The Status and Prospects of Epstein–Barr Virus Prophylactic Vaccine Development

“…Since the licensed VZV vaccine took the first step in clinical herpes virus immunization, it has brought home the lesson that appropriate adjuvants used in vaccine formulation can greatly enhance the immunization efficacy. Additionally, the rising application of specific toll-like receptor (TLR) agonists (134)(135)(136) provides additional alternatives in the selection of adjuvants to achieve specific immunization responses.…”