InVivoPlus human IgG1 isotype control

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) evolution reduces the efficacy of prophylactic vaccines and monoclonal antibody (mAb) therapies. To evaluate potency and breadth, receptor binding domain (RBD)-targeting neutralizing mAbs were identified from patient B cells using an Omicron KP3.1.1 Spike (S) protein bait. MAbs exhibiting the greatest neutralization potency (1332D4 and 1332E5) and binding breadth (1324A10 and 1316C10) were evaluated in greater detail. Cryo-electron microscopy (Cryo-EM) studies revealed 1332D4 and 1332E5 target RBD residue segments 439-446 and 498-506 of KP3.1.1 S, respectively. 1332E5 is a knob498-506-targeting class-1/4 mAb that exhibits pan-Omicron specificity but does not bind or neutralize ancestral Wuhan-1. Further analysis suggests mAbs generically defined as class 1/4 mAbs may be separated into two classes. Class 1/4 mAbs, like 1332E5, and class 4/1 mAbs that make extensive interactions with the class-4 epitope and limited contacts with the class-1 knob498-596. Despite these differences, the specificity of both mAb classes can be altered by mutations in knob498-506.

Cytokine Release Syndrome (CRS) is a life-threatening complication of T-cell-engaging immunotherapies, causing vascular leakage and multi-organ dysfunction. Standard Interleukin-6 (IL-6) blockade often fails in severe cases by leaving the upstream initiator, Tumor Necrosis Factor-α (TNF-α), unchecked. TNF-α drives early macrophage activation and endothelial injury, whereas IL-6 amplifies systemic inflammation. To decisively interrupt this inflammatory feedback loop, we developed IDC007, a novel bispecific antibody simultaneously neutralizing TNF-α and IL-6 receptor (IL-6R).

Programmed cell death-1 (PD-1) is a co-inhibitory receptor expressed on T cells that dampens TCR and CD28 signaling in the immunological synapse. PD-1 is significantly upregulated on T cells in the tumor microenvironment, where it promotes exhaustion in the context of chronic antigen restimulation. Exhaustion renders T cells hyporesponsive and ineffectual, but potentially resistant to restimulation-induced cell death (RICD). Restimulation-induced cell death (RICD) is a critical propriocidal apoptosis program triggered in activated T cells upon robust TCR re-engagement, which serves to constrain effector T cell expansion and longevity to prevent collateral tissue damage. While the checkpoint function of PD-1 has profound implications for cancer immunotherapy, the role of PD-1 in regulating newly activated T cells remains unclear. We hypothesized that PD-1 attenuates RICD sensitivity in human effector T cells by modulating TCR signal strength. Here we show that transient upregulation of PD-1 helps to protect clonally expanding human CD4+ and CD8 + T cells from premature RICD, with only moderate protection noted in terminally-differentiated, PD-1lo effector CD8 + T cells. Restimulation of T cells with beads containing PD-L1 results in significant apoptosis resistance, dependent on PD-L1 dosage and the proximity of PD-L1 to the TCR and CD28. Interestingly, PD-L1 demonstrated a more significant RICD rescue with CD28 co-ligation as opposed to TCR engagement alone, suggesting PD-1 signaling targets both signaling pathways in this context. Furthermore, biochemical/proteomic data suggest PD-1 modulates proximal signaling downstream of both TCR and CD28 and influences the expression of specific pro/anti-apoptotic proteins that govern RICD sensitivity. Despite the original assumption of PD-1 as a programmed death-inducing protein, our research reveals that homeostatic expression of PD-1 in clonally expanding T cells confers RICD resistance that promotes T cell survival and persistence. These findings present significant implications for understanding how blocking or engaging the PD-L1:PD-1 signaling axis may influence apoptosis sensitivity in both normal and exhausted T cells to alter adaptive immune responses.