Antagonism of the Platelet-Activating Factor Pathway Mitigates Inflammatory Adverse Events Driven by Anti-erythrocyte Antibody Therapy in Mice.

Immune thrombocytopenia (ITP) is an autoimmune disease characterized by low platelet counts primarily due to antiplatelet autoantibodies. Anti-D is a donor-derived polyclonal Ab against the rhesus D Ag on erythrocytes used to treat ITP. Unfortunately, adverse inflammatory/hypersensitivity reactions and a Food and Drug Administration-issued black box warning have limited its clinical use.

Human Fc gamma receptor IIIA blockade inhibits platelet destruction in a humanized murine model of ITP.

Fc gamma receptor (FcγR) IIIA is an important receptor for immunoglobulin G (IgG) and is involved in immune defense mechanisms as well as tissue destruction in some autoimmune diseases including immune thrombocytopenia (ITP). FcγRIIIA on macrophages can trigger phagocytosis of IgG-sensitized platelets, and prior pilot studies observed blockade of FcγRIIIA increased platelet counts in patients with ITP. Unfortunately, although blockade of FcγRIIIA in patients with ITP increased platelet counts, its engagement by the blocking antibody drove serious adverse inflammatory reactions.

Unveiling Sticholysin II and plasmid DNA interaction: Implications for developing non-viral vectors.

Non-viral gene delivery systems offer significant potential for gene therapy due to their versatility, safety, and cost advantages over viral vectors. However, their effectiveness can be hindered by the challenge of efficiently releasing the genetic cargo from endosomes to prevent degradation in lysosomes. To overcome this obstacle, functional components can be incorporated into these systems.

Trogocytosis drives red blood cell antigen loss in association with antibody-mediated immune suppression.

Red blood cell (RBC) alloimmunization to paternal antigens during pregnancy can cause hemolytic disease of the fetus and newborn (HDFN). This severe and potentially fatal neonatal disorder can be prevented by the administration of polyclonal anti-D through a mechanism referred to as antibody-mediated immune suppression (AMIS). Although anti-D prophylaxis effectively prevents HDFN, a lack of mechanistic clarity has hampered its replacement with recombinant agents.

Antigen copy number and antibody dose can determine the outcome of erythrocyte alloimmunization inducing either antibody-mediated immune suppression or enhancement in a murine model.

Background: The administration of anti-D for the prevention of hemolytic disease of the fetus and newborn is one of the most successful clinical uses of the phenomenon of antibody-mediated immune suppression (AMIS). However, despite adequate prophylaxis, failures can still occur in the clinic and are poorly understood. Recently, the copy number of red blood cell (RBC) antigens has been shown to influence immunogenicity in the context of RBC alloimmunization; however, its influence on AMIS remains unexplored.

Antigen-specific IgG subclass composition in recipient mice can indicate the degree of red blood cell alloimmunization as well as discern between primary and secondary immunization.

Background: Despite the vast antigen disparity between donor and recipient red blood cells (RBCs), only 2%-6% of transfusion patients mount an alloantibody response. Recently, RBC antigen density has been proposed as one of the factors that can influence alloimmunization, however, there has been no characterization of the role of antigen density along with RBC dose in primary and secondary immunization.

Study Design And Methods: To generate RBCs that express distinct antigen copy numbers, different quantities of hen egg lysozyme (HEL) were coupled to murine RBCs.

THP-1 cells transduced with CD16A utilize Fcγ receptor I and III in the phagocytosis of IgG-sensitized human erythrocytes and platelets.

Fc gamma receptors (FcγRs) are critical effector receptors for immunoglobulin G (IgG) antibodies. On macrophages, FcγRs mediate multiple effector functions, including phagocytosis, but the individual contribution of specific FcγRs to phagocytosis has not been fully characterized. Primary human macrophage populations, such as splenic macrophages, can express FcγRI, FcγRIIA, and FcγRIIIA.

Sticholysins, pore-forming proteins from a marine anemone can induce maturation of dendritic cells through a TLR4 dependent-pathway.

Sticholysins (Sts) I and II (StI and StII) are pore-forming proteins (PFPs), purified from the Caribbean Sea anemone Stichodactyla helianthus. StII encapsulated into liposomes induces a robust antigen-specific cytotoxic CD8 T lymphocytes (CTL) response and in its free form the maturation of bone marrow-derived dendritic cells (BM-DCs). It is probable that the latter is partially supporting in part the immunomodulatory effect on the CTL response induced by StII-containing liposomes.

Treating murine inflammatory diseases with an anti-erythrocyte antibody.

Treatment of autoimmune and inflammatory diseases typically involves immune suppression. In an opposite strategy, we show that administration of the highly inflammatory erythrocyte-specific antibody Ter119 into mice remodels the monocyte cellular landscape, leading to resolution of inflammatory disease. Ter119 with intact Fc function was unexpectedly therapeutic in the K/BxN serum transfer model of arthritis.

The Vacuolar Pathway in Macrophages Plays a Major Role in Antigen Cross-Presentation Induced by the Pore-Forming Protein Sticholysin II Encapsulated Into Liposomes.

Cross-presentation is an important mechanism for the differentiation of effector cytotoxic T lymphocytes (CTL) from naïve CD8 T-cells, a key response for the clearance of intracellular pathogens and tumors. The liposomal co-encapsulation of the pore-forming protein sticholysin II (StII) with ovalbumin (OVA) (Lp/OVA/StII) induces a powerful OVA-specific CTL activation and an anti-tumor response . However, the pathway through which the StII contained in this preparation is able to induce antigen cross-presentation and the type of professional antigen presenting cells (APCs) involved have not been elucidated.

Erythrocyte Saturation with IgG Is Required for Inducing Antibody-Mediated Immune Suppression and Impacts Both Erythrocyte Clearance and Antigen-Modulation Mechanisms.

Anti-D prevents hemolytic disease of the fetus and newborn, and this mechanism has been referred to as Ab-mediated immune suppression (AMIS). Anti-D, as well as other polyclonal AMIS-inducing Abs, most often induce both epitope masking and erythrocyte clearance mechanisms. We have previously observed that some Abs that successfully induce AMIS effects could be split into those that mediate epitope masking versus those that induce erythrocyte clearance, allowing the ability to analyze these mechanisms separately.

Prevention of hemolytic disease of the fetus and newborn: what have we learned from animal models?

Purpose Of Review: This review aims to highlight recent advances in our understanding of how anti-red blood cell (RBC) antibodies prevent erythrocyte immunization with an emphasis on new murine models.

Recent Findings: New murine models with clinically relevant human erythrocyte antigens have been used to understand the alloimmunization process and its inhibition. The search to elucidate the mechanism of action of IgG-mediated inhibition of erythrocyte alloimmunization has provided new evidence in support of a potential role for epitope masking, immune deviation and/or antigen modulation in this process.

Phosphocholine-Specific Antibodies Improve T-Dependent Antibody Responses against OVA Encapsulated into Phosphatidylcholine-Containing Liposomes.

Liposomes containing phosphatidylcholine have been widely used as adjuvants. Recently, we demonstrated that B-1 cells produce dipalmitoyl-phosphatidylcholine (DPPC)-specific IgM upon immunization of BALB/c mice with DPPC-liposomes encapsulating ovalbumin (OVA). Although this preparation enhanced the OVA-specific humoral response, the contribution of anti-DPPC antibodies to this effect was unclear.

Role of B-1 cells in the immune response against an antigen encapsulated into phosphatidylcholine-containing liposomes.

B-1 lymphocytes comprise a unique subset of B cells that differ phenotypically, ontogenetically and functionally from conventional B-2 cells. A frequent specificity of the antibody repertoire of peritoneal B-1 cells is phosphatidylcholine. Liposomes containing phosphatidylcholine have been studied as adjuvants and their interaction with dendritic cells and macrophages has been demonstrated.

Liposomes of phosphatidylcholine and cholesterol induce an M2-like macrophage phenotype reprogrammable to M1 pattern with the involvement of B-1 cells.

Macrophages respond to endogenous and non-self stimuli acquiring the M1 or M2 phenotypes, corresponding to classical or alternative activation, respectively. The role of B-1 cells in the regulation of macrophage polarization through the secretion of interleukin (IL)-10 has been demonstrated. However, the influence of B-1 cells on macrophage phenotype induction by an immunogen that suppress their ability to secrete IL-10 has not been explored.

Study of various presentation forms for a peptide mimetic of Neisseria meningitidis serogroup B capsular polysaccharide.

The formulation of a broadly protective vaccine to prevent the serogroup B Neisseria meningitidis (MenB) disease is still an unmet medical need. We have previously reported the induction of bactericidal and protective antibodies against MenB after immunization of mice with a phage-displayed peptide named 4 L-5. This peptide mimics a capsular polysaccharide (CPS) epitope in MenB.

Identification and characterization of phage-displayed peptide mimetics of Neisseria meningitidis serogroup B capsular polysaccharide.

Neisseria meningitidis causes meningitis and septicemia. There is no single vaccine against all serogroup B meningococcal (MenB) strains up to now. Their capsular polysaccharide (MenB CPS) bears epitopes both cross-reacting and non-cross-reactive with human polysialic acid.

Purified capsular polysaccharide of Neisseria meningitidis serogroup A as immune potentiator for antibody production.

The development of new immune potentiators for human vaccines is an important and expanding field of research. In the present study, the ability of the capsular polysaccharide from Neisseria meningitidis serogroup A (CPS-A), a mannose-containing carbohydrate, to enhance the antibody production against a co-administered model vaccine antigen, is examined. A protein-meningococcal serogroup C capsular polysaccharide (CPS-C) conjugate was selected as the model antigen for this study.

Enzyme-linked immunosorbent assay for quantitative determination of capsular polysaccharide production in Streptococcus pneumoniae clinical isolates.

A simple, specific, sensitive and reproducible ELISA has been developed to quantify the level of CPS (capsular polysaccharide) production in supernatants of Streptococcus pneumoniae cell cultures. CPSs from Strep. pneumoniae have been widely used as vaccine antigens.