Lipidoid Nanoparticles Containing PD-L1 siRNA Delivered In Vivo Enter Kupffer Cells and Enhance NK and CD8+ T Cell-mediated Hepatic Antiviral Immunity

Abstract

Effective clinical application of antiviral immunotherapies necessitates enhancing the functional state of natural killer (NK) and CD8+ T cells. An important mechanism for the establishment of viral persistence in the liver is the activation of the PD-1/PD-L1 inhibitory pathway. To examine the role of hepatic myeloid PD-L1 expression during viral infection, we determined the magnitude and quality of antiviral immune responses by administering PD-L1 short-interfering RNA (siRNA) encapsulated in lipidoid nanoparticles (LNP) in mice. Our studies indicate that Kupffer cells (KC) preferentially engulfed PD-L1 LNP within a short period of time and silenced Pdl1 during adenovirus and MCMV infection leading to enhanced NK and CD8+ T cell intrahepatic accumulation, effector function (interferon (IFN)-γ and granzyme B (GrB) production), CD8+ T cell–mediated viral clearance, and memory. Our results demonstrate that PD-L1 knockdown on KCs is central in determining the outcome of liver viral infections, and they represent a new class of gene therapy.

Combination Immune Therapies to Enhance Anti-Tumor Responses by NK Cells

“…In the case of viral persistence in the liver, the abrogation of PD-L1 by siRNA was shown to enhance the number of intrahepatic NK cells and CTL, thereby increasing cytotoxicity, cytokine production, viral clearance, and memory (148). During HIV infection, PD-1 levels increase on patient NK cells, and this has been shown to diminish NK cell proliferation (145).…”

Delivery strategies and potential targets for siRNA in major cancer types

“…Silencing of Pdl1 effectively enhanced the NK cell and CD8+ T cell intrahepatic accumulation, viral clearance, and CD8+ T cell memory to hepatotropic viral infection. This study demonstrated that transient knockdown of PD-L1 using siRNA directly on the disease-causing cell type might even have benefits when compared to monoclonal antibody usage [158]. …”

Intrahepatic regulation of antiviral T cell responses at initial stages of viral infection

“…Importantly, KCs contribute to liver Treg cell-derived IL-10 production [20], and HBV particles also induce TGF-β production by KCs and probably promote Treg cell differentiation [50]. Beside IL-10 and TGF-β-mediated liver immune tolerance, activated KCs inhibit liver T cell responses through upregulation of co-inhibitory molecules [18]. By delivering the lipidoid nanoparticles carrying PD-L1 siRNA to KCs in vivo, Dolina et al demonstrated that silence of PD-L1 in KCs during Ad and murine cytomegalovirus (MCMV) infection resulted in enhanced hepatic CD8 T cell accumulation, effector cytokine production, and viral clearance [18].…”

“…Beside IL-10 and TGF-β-mediated liver immune tolerance, activated KCs inhibit liver T cell responses through upregulation of co-inhibitory molecules [18]. By delivering the lipidoid nanoparticles carrying PD-L1 siRNA to KCs in vivo, Dolina et al demonstrated that silence of PD-L1 in KCs during Ad and murine cytomegalovirus (MCMV) infection resulted in enhanced hepatic CD8 T cell accumulation, effector cytokine production, and viral clearance [18]. It is also reported that PD-1 expression is associated with CD8 T cell exhaustion in acute HCV infection [51].…”

“…HSCs and KCs can express anti-inflammatory cytokines, such as IL-10 and TGFβ, to inhibit T cell activation and proliferation [12–14]. The co-inhibitory molecules PD-L1 have been detected in several liver cell populations, including hepatocytes, HSCs, KCs and LSECs, contributing to the inhibition of effector T cell functions and T cell exhaustion [15–18]. HSCs and KCs are also reported to support Treg cell differentiation and cytokine production, leading to impaired liver T cell responses [19, 20].…”