GNUV201, a novel human/mouse cross-reactive and low pH-selective anti-PD-1 monoclonal antibody for cancer immunotherapy.

BACKGROUND: Several PD-1 antibodies approved as anti-cancer therapies work by blocking the interaction of PD-1 with its ligand PD-L1, thus restoring anti-cancer T cell activities. These PD-1 antibodies lack inter-species cross-reactivity, necessitating surrogate antibodies for preclinical studies, which may limit the predictability and translatability of the studies. RESULTS: To overcome this limitation, we have developed an inter-species cross-reactive PD-1 antibody, GNUV201, by utilizing an enhanced diversity mouse platform (SHINE MOUSE™). GNUV201 equally binds to human PD-1 and mouse PD-1, equally inhibits the binding of human PD-1/PD-L1 and mouse PD-1/PD-L1, and effectively suppresses tumor growth in syngeneic mouse models. The epitope of GNUV201 mapped to the "FG loop" of hPD-1, distinct from those of Keytruda® ("C'D loop") and Opdivo® (N-term). Notably, the structural feature where the protruding epitope loop fits into GNUV201's binding pocket supports the enhanced binding affinity due to slower dissociation (8.7 times slower than Keytruda®). Furthermore, GNUV201 shows a stronger binding affinity at pH 6.0 (5.6 times strong than at pH 7.4), which mimics the hypoxic and acidic tumor microenvironment (TME). This phenomenon is not observed with marketed antibodies (Keytruda®, Opdivo®), implying that GNUV201 achieves more selective binding to and better occupancy on PD-1 in the TME. CONCLUSIONS: In summary, GNUV201 exhibited enhanced affinity for PD-1 with slow dissociation and preferential binding in TME-mimicking low pH. Human/monkey/mouse inter-species cross-reactivity of GNUV201 could enable more predictable and translatable efficacy and toxicity preclinical studies. These results suggest that GNUV201 could be an ideal antibody candidate for anti-cancer drug development.

Aminoacyl transfer ribonucleic acid synthetase complex-interacting multifunctional protein 1 induces microglial activation and M1 polarization via the mitogen-activated protein kinase/nuclear factor-kappa B signaling pathway.

Activation of microglia, which is the primary immune cell of the central nervous system, plays an important role in neuroinflammation associated with several neuronal diseases. Aminoacyl tRNA synthetase (ARS) complex-interacting multifunctional protein 1 (AIMP1), a structural component of the multienzyme ARS complex, is secreted to trigger a pro-inflammatory function and has been associated with several inflammatory diseases. However, the effect of AIMP1 on microglial activation remains unknown. AIMP1 elevated the expression levels of activation-related cell surface markers and pro-inflammatory cytokines in primary and BV-2 microglial cells. In addition to the AIMP1-mediated increase in the expression levels of M1 markers [interleukin (IL)-6, tumor necrosis factor-α, and IL-1ß], the expression levels of CD68, an M1 cell surface molecule, were also increased in AIMP-1-treated microglial cells, while those of CD206, an M2 cell surface molecule, were not, indicating that AIMP1 triggers the polarization of microglial cells into the M1 state but not the M2 state. AIMP1 treatment induced the phosphorylation of mitogen-activated protein kinases (MAPKs), while MAPK inhibitors suppressed the AIMP1-induced microglial cell activation. AIMP1 also induced the phosphorylation of the nuclear factor-kappa B (NF-κB) components and nuclear translocation of the NF-κB p65 subunit in microglial cells. Furthermore, c-Jun N-terminal kinase (JNK) and p38 inhibitors markedly suppressed the AIMP1-induced phosphorylation of NF-κB components as well as the nuclear translocation of NF-κB p65 subunit, suggesting the involvement of JNK and p38 as upstream regulators of NF-κB in AIMP1-induced microglial cell activation. The NF-κB inhibitor suppressed the AIMP1-induced M1 polarization of the microglial cells. Taken together, AIMP1 effectively induces M1 microglial activation via the JNK and p38/NF-κB-dependent pathways. These results suggest that AIMP1 released under stress conditions may be a pathological factor that induces neuroinflammation.

Threonyl-tRNA Synthetase Promotes T Helper Type 1 Cell Responses by Inducing Dendritic Cell Maturation and IL-12 Production via an NF-κB Pathway.

Threonyl-tRNA synthetase (TRS) is an aminoacyl-tRNA synthetase that catalyzes the aminoacylation of tRNA by transferring threonine. In addition to an essential role in translation, TRS was extracellularly detected in autoimmune diseases and also exhibited pro-angiogenetic activity. TRS is reported to be secreted into the extracellular space when vascular endothelial cells encounter tumor necrosis factor-α. As T helper (Th) type 1 response and IFN-γ levels are associated with autoimmunity and angiogenesis, in this study, we investigated the effects of TRS on dendritic cell (DC) activation and CD4 T cell polarization. TRS-treated DCs exhibited up-regulated expression of activation-related cell-surface molecules, including CD40, CD80, CD86, and MHC class II. Treatment of DCs with TRS resulted in a significant increase of IL-12 production. TRS triggered nuclear translocation of the NF-κB p65 subunit along with the degradation of IκB proteins and the phosphorylation of MAPKs in DCs. Additionally, MAPK inhibitors markedly recovered the degradation of IκB proteins and the increased IL-12 production in TRS-treated DCs, suggesting the involvement of MAPKs as the upstream regulators of NF-κB in TRS-induced DC maturation and activation. Importantly, TRS-stimulated DCs significantly increased the populations of IFN-γ+CD4 T cells, and the levels of IFN-γ when co-cultured with CD4+ T cells. The addition of a neutralizing anti-IL-12 mAb to the cell cultures of TRS-treated DCs and CD4+ T cells resulted in decreased IFN-γ production, indicating that TRS-stimulated DCs may enhance the Th1 response through DC-derived IL-12. Injection of OT-II mice with OVA-pulsed, TRS-treated DCs also enhanced Ag-specific Th1 responses in vivo. Importantly, injection with TRS-treated DC exhibited increased populations of IFN-γ+-CD4+ and -CD8+ T cells as well as secretion level of IFN-γ, resulting in viral clearance and increased survival periods in mice infected with influenza A virus (IAV), as the Th1 response is associated with the enhanced cellular immunity, including anti-viral activity. Taken together, these results indicate that TRS promotes the maturation and activation of DCs, DC-mediated Th1 responses, and anti-viral effect on IAV infection.

IL-33 changes CD25hi Tregs to Th17 cells through a dendritic cell-mediated pathway.

Interleukin (IL)-33 is an alarmin factor that is highly secreted in a variety of autoimmune diseases, induces maturation of dendritic cells (DCs) and differentiation of T helper 17 (Th17) cells. As the balance between Th17 cells and regulatory T cells (Tregs) is important to maintain immune homeostasis, in this study, we investigated the effects of IL-33 on Treg cell response. We observed that direct treatment with IL-33 had no effect on Treg differentiation, whereas IL-33-matured DCs (IL33-matDCs) inhibited the differentiation of CD4+ T cells to Tregs by decreasing the expression of Foxp3. Furthermore, co-culture with IL-33-matDCs changed stable Tregs (CD25hiCD4+ Tregs) to IL-17-producing cells, whereas IL-33-matDCs had little effects on unstable Tregs (CD25loCD4+ Tregs). The stable Tregs were demonstrated to express high levels of IL-6 receptors. Blocking of IL-6 secreted from IL-33-matDCs suppressed the conversion of Tregs to Th17 cells, indicating the greater propensity to convert stable Tregs to Th17 cells is due to IL-6 signaling. Taken together, these results demonstrate that IL-33 inhibits Treg differentiation and the conversion of stable Tregs to Th17 cells via DCs.

Mst1-Deficiency Induces Hyperactivation of Monocyte-Derived Dendritic Cells via Akt1/c-myc Pathway.

Mst1 is a multifunctional serine/threonine kinase that is highly expressed in several immune organs. The role of Mst1 in the activation of dendritic cells (DCs), a key player of adaptive immunity, is poorly understood. In this study, we investigated the role of Mst1 in GM-CSF-induced bone marrow-derived DCs and the underlying mechanisms. Mst1-/- DCs in response to GM-CSF expressed higher levels of activation/maturation-related cell surface molecules, such as B7 and MHC class II than Mst1+/+ DCs. Furthermore, the expression of proinflammatory cytokines, such as IL-23, TNF-α, and IL-12p40, was increased in Mst1-/- DCs, indicating that Mst1-deficiency may induce the hyperactivation of DCs. Additionally, Mst1-/- DCs exhibited a stronger capacity to activate allogeneic T cells than Mst1+/+ DCs. Silencing of Mst1 in DCs promoted their hyperactivation, similar to the phenotypes of Mst1-/- DCs. Mst1-/- DCs exhibited an increase in Akt1 phosphorylation and c-myc protein levels. In addition, treatment with an Akt1 inhibitor downregulated the protein level of c-myc increased in Mst1-deficient DCs, indicating that Akt1 acts as an upstream inducer of the de novo synthesis of c-myc. Finally, Akt1 and c-myc inhibitors downregulated the increased expression of IL-23p19 observed in Mst1-knockdown DCs. Taken together, these data demonstrate that Mst1 negatively regulates the hyperactivation of DCs through downregulation of the Akt1/c-myc axis in response to GM-CSF, and suggest that Mst1 is one of the endogenous factors that determine the activation status of GM-CSF-stimulated inflammatory DCs.

Atializumab, a humanized anti-aminoacyl-tRNA synthetase-interacting multifunctional protein-1 (AIMP1) antibody significantly improves nephritis in (NZB/NZW) F1 mice.

Aminoacyl-tRNA synthetase (ARS)-interacting multifunctional protein 1 (AIMP1) enhances the expression of proinflammatory cytokines. In our previous study, we have shown that serum AIMP1 in patients with SLE was significantly higher than that of healthy controls. To address whether neutralization of AIMP1 could ameliorate nephritis in lupus-prone mice, we generated atializumab, a humanized antibody against AIMP1 and investigated its therapeutic efficacy. ELISA showed that serum AIMP1 at 23 weeks old was significantly higher than that at 13 weeks old in lupus-prone mice. Therefore, lupus-prone mice were randomly assigned to 5 groups (vehicle, methylprednisolone and 0.5, 2, and 5 mg/kg atializumab). After treatment, disease severity was assessed using a variety of phenotypes, including proteinuria, histological damages, renal deposition of immune-complex. In addition, serum cytokines, anti-dsDNA and IgG subclasses were determined. T cell subsets were analyzed using a fluorescence-activated cell sorter. Atializumab significantly diminished proteinuria, improved glomerular and tubular damages and reduced the renal deposition of immune-complexes. Moreover, atializumab significantly decreased serum interferon (IFN)-γ, interleukin (IL)-17A, and IL-6, whereas it increased serum IL-10. Similarly, atializumab reduced the numbers of TH1, TH2 and TH17 cells in a dose-dependent manner, while atializumab enhanced the number of regulatory T (Treg) cells. Furthermore, atializumab decreased not only splenic plasma cells and serum anti-dsDNA but also pathogenic IgG subclasses for nephritis. It suppressed NF-κB activation by inhibiting IκBα degradation in a dose-dependent manner in vitro. Atializumab alleviated nephritis by inhibiting autoreactive T, B, and plasma cells and decreasing NF-κB-related proinflammatory cytokines in lupus-prone mice. These results suggest that treatment targeting AIMP1 could be a novel and highly immune-modulating therapeutic strategy in lupus nephritis.

Lysyl-Transfer RNA Synthetase Induces the Maturation of Dendritic Cells through MAPK and NF-κB Pathways, Strongly Contributing to Enhanced Th1 Cell Responses.

In addition to essential roles in protein synthesis, lysyl-tRNA synthetase (KRS) is secreted to trigger a proinflammatory function that induces macrophage activation and TNF-α secretion. KRS has been associated with autoimmune diseases such as polymyositis and dermatomyositis. In this study, we investigated the immunomodulatory effects of KRS on bone marrow-derived dendritic cells (DCs) of C57BL/6 mice and subsequent polarization of Th cells and analyzed the underlying mechanisms. KRS-treated DCs increased the expression of cell surface molecules and proinflammatory cytokines associated with DC maturation and activation. Especially, KRS treatment significantly increased production of IL-12, a Th1-polarizing cytokine, in DCs. KRS triggered the nuclear translocation of the NF-κB p65 subunit along with the degradation of IκB proteins and the phosphorylation of MAPKs in DCs. Additionally, JNK, p38, and ERK inhibitors markedly recovered the degradation of IκB proteins, suggesting the involvement of MAPKs as the upstream regulators of NF-κB in the KRS-induced DC maturation and activation. Importantly, KRS-treated DCs strongly increased the differentiation of Th1 cells when cocultured with CD4+ T cells. The addition of anti-IL-12-neutralizing Ab abolished the secretion of IFN-γ in the coculture, indicating that KRS induces Th1 cell response via DC-derived IL-12. Moreover, KRS enhanced the OVA-specific Th1 cell polarization in vivo following the adoptive transfer of OVA-pulsed DCs. Taken together, these results indicated that KRS effectively induced the maturation and activation of DCs through MAPKs/NF-κB-signaling pathways and favored DC-mediated Th1 cell response.