Harnessing SLE Autoantibodies for Intracellular Delivery of Biologic Therapeutics

Antibodies were thought to be unable to penetrate inside the cytosol and intracellular compartments. This concept was challenged by the discovery of naturally occurring systemic lupus erythematosus (SLE) antibodies that localize intracellularly. Understanding the mechanisms of the intracellular localization of these unique molecules is crucial for the engineering of intracellular therapeutic monoclonal antibodies (mAbs), which so far do not exist. Endosomal entrapment and persistence in the cytosol are major challenges facing mAbs inside the cell. SLE antibodies naturally evolved to overcome these challenges. Recent studies shed light on mechanisms of endosomal escape and were used to engineer biologics for intracellular targeting. The introduction of an endosomal escape motif, coupling with DNA, adjusting antibody charge, and disabled tripartite motif-containing 21-mediated antibody degradation offer new insights on antibody engineering for intracellular targeting. Intracellular delivery of therapeutic antibodies is highly desirable but remains a challenge for biomedical research and the pharmaceutical industry. Approximately two-thirds of disease-associated targets are found inside the cell. Difficulty blocking these targets with available drugs creates a need for technology to deliver highly specific therapeutic antibodies intracellularly. Historically, antibodies have not been believed to traverse the cell membrane and neutralize intracellular targets. Emerging evidence has revealed that anti-DNA autoantibodies found in systemic lupus erythematosus (SLE) patients can penetrate inside the cell. Harnessing this technology has the potential to accelerate the development of drugs against intracellular targets. Here, we dissect the mechanisms of the intracellular localization of SLE antibodies and discuss how to apply these insights to engineer successful cell-penetrating antibody drugs. Intracellular delivery of therapeutic antibodies is highly desirable but remains a challenge for biomedical research and the pharmaceutical industry. Approximately two-thirds of disease-associated targets are found inside the cell. Difficulty blocking these targets with available drugs creates a need for technology to deliver highly specific therapeutic antibodies intracellularly. Historically, antibodies have not been believed to traverse the cell membrane and neutralize intracellular targets. Emerging evidence has revealed that anti-DNA autoantibodies found in systemic lupus erythematosus (SLE) patients can penetrate inside the cell. Harnessing this technology has the potential to accelerate the development of drugs against intracellular targets. Here, we dissect the mechanisms of the intracellular localization of SLE antibodies and discuss how to apply these insights to engineer successful cell-penetrating antibody drugs. antibodies produced by individuals’ plasma cells against self-antigens. amino acid sequences on variable chains of antibodies that form an antigen-binding site. There are three CDRs per variable domain in an antibody. an active transport mechanism that brings substances encapsulated in endocytic vesicles inside the cell. There are three main endocytic pathways – phagocytosis (large particle transport), pinocytosis (liquid transport), receptor-mediated endocytosis (clathrin-mediated transport), and caveolae (clathrin-independent transport). release of endocytosed cargo from the endosome mediated by a breach in the endocytic membrane. Endosomal escape is often triggered by reduced pH in the endosome. correlation analysis of fluctuations of the fluorescence intensity. FCS provides concentration fluctuations for fluorescent particles (molecules) in a solution based on the diffusion rate. FCS is used to measure the concentration of fluorescently labeled molecules in the cytoplasm of live cells. a proteoglycan in which two or three heparan sulfate chains are attached to the cell surface or extracellular matrix proteins. HSPG was shown to act as a cellular receptor for various ligands and to function in cellular signaling. a member of the small GTPase Ras family (including HRas, NRas, and KRas). KRas is part of the RAS/MAPK signaling pathway and plays a key role in cell proliferation. KRas is the most common oncogene and is associated with the oncogenesis of many human malignancies including pancreatic, colorectal, lung, and prostate cancers. protein molecules that are produced by identical cells that derive from same parental clone. In the laboratory setting, mAbs are produced by a hybridoma line (fusion of murine B and myeloid cells). mAbs are IgG molecules that bind to monovalent extracellular targets to agonize, antagonize, or deplete them and are widely used to treat cancers and autoimmune and neurologic diseases. a coating of a particle (often a virus or bacterium) with antibodies to mediate phagocytosis by macrophages or dendritic cells. a systemic autoimmune disease mediated by a robust immune response against self-antigens. SLE affects the skin, joints, kidney, brain, and other organs. A high titer of autoantibodies is found in the majority of SLE patients and is associated with inflammation. SLE’s etiology is elusive and all therapies are symptomatic. a cytosolic ubiquitin ligase that belongs to the TRIM family of single-protein RING-finger E3 ubiquitin protein ligases. TRIM21 functions as an antibody Fc receptor that mediates proteasomal degradation and provides protection against opsonized particles that have invaded the cytosol.