Follicular Helper T (TFH) Cell Targeting by TLR8 Signaling For Improving HBsAg-Specific B Cell Response In Chronic Hepatitis B Patients

Abstract

Identifying signaling pathways that induce B cell response can aid functional cure strategies for chronic hepatitis B infection (CHB). TLR8 activation with ssRNA was shown to enhance follicular helper T cell (TFH) function leading to improved B cell responses in vitro. We investigated whether this mechanism can rescue an exhausted immune response in CHB infection. Effect of TLR8 agonism on supporting cytokines and TFH and B cells were evaluated using ex vivo and in vitro assays. The ability of an oral TLR8 agonist to promote TFH and B cell response was tested in samples from phase 1b clinical trial. TLR8 agonism induced TFH polarizing cytokine IL-12 in monocytes. Treatment of peripheral blood mononuclear cells (PBMCs) from CHB patients with TLR8 agonists induced cytokine IL-21 by TFH cells with enhanced IL-21+BCL-6+ and ICOS+BCL-6+ co-expression. Mechanistically, incubation of isolated naïve CD4+ T cells with TLR8 triggered monocytes resulted in their differentiation into IL-21+ICOS+BCL-6+ TFH in an IL-12 dependent manner. Furthermore, co-culture of these IL-21 producing TFH with autologous naïve B cells led to enhanced memory (CD19+CD27+) and plasma B cell generation (CD19+CD27++CD38+) and IgG production. Importantly, in TFH from CHB patients treated with an oral TLR8 agonist, HBsAg-specific BCL-6, ICOS, IL-21 and CD40L expression and rescue of defective activation induced marker (AIM) response along with partial restoration of HBsAg-specific B cell ELISPOT response was evident. TLR8 agonism can thus enhance HBV-specific B cell responses in CHB patients by improving monocyte-mediated TFH function and may play a role in achieving HBV functional cure.

Immune Mechanisms Underlying Hepatitis B Surface Antigen Seroclearance in Chronic Hepatitis B Patients With Viral Coinfection

“…The phenotypic and functional differences between HBsAg and hepatitis B core antigen (HBcAg) specific B cells in a same patient suggest that high levels of HBsAg may lead to programming obstacles of HBsAg specific B cells through continuous stimulation. Follicular helper T cell can improving HBsAg-specific B cell response in chronic hepatitis B patients targeting by TLR8 signaling ( 40 ).…”

Research Progress on the Mechanism of Persistent Low-Level HBsAg Expression in the Serum of Patients with Chronic HBV Infection

“…At the same time, it has been reported that NK cells in patients with chronic HBV infection can mediate immune tolerance or immune injury [ 93 ]. Other studies have shown that HBsAg can interfere with toll-like receptors (TLRs) in the monocyte/macrophage signaling pathway to inhibit the release of cytokines, which may help to establish a chronic infection [ 94 , 95 ]. However, Kim et al [ 86 ] have shown that there is no significant difference in the composition of immune cells between monocytes and NK cells in the serum low-level HBsAg group and serum high-level HBsAg group.…”

Oral Selective TLR8 Agonist Selgantolimod Induces Multiple Immune Cell Responses in Humans

“…To investigate immunophenotyping by flow cytometry [8], PBMCs from BL and 8 h post-selgantolimod treatment were thawed, and after washing, 0.5-1 × 10 6 cells/panel were labeled with antibodies (flow panels listed in Table S1) at 4 • C for 30 min. After staining, cells were washed twice with FACS buffer (1× PBS/2% FBS), followed by fixation with 2% paraformaldehyde.…”

“…Preclinical and clinical studies have shown that downstream inflammatory immune mediators from TLR8 signaling result in preliminary efficacy for the treatment of cancer and viral infections [7]. Recently, we reported that in CHB patients, TLR8 signaling upregulated the follicular helper T (T FH ) cell functions and rescued the exhausted phenotypes in an IL-12-dependent manner [8].…”

“…Selgantolimod (SLGN), previously known as GS-9688, is a novel and potent selective small-molecule TLR8 agonist developed for potential use in chronic HBV therapy [15]. SLGN oral treatment improved HBsAg-specific B cell responses by enhancing the follicular helper T (T FH ) cell functions via IL-12-dependent manner in a subset of CHB patients [8]. In a woodchuck model of CHB, SLGN administration induced pro-inflammatory cytokines IL-12p40, IL-18, IL-6, IL-1RA as well as antiviral cytokines TNFα and IFNγ and had an antiviral effect [16].…”