2001

2001. When combined, the antibodies Mouse monoclonal to TrkA had additive neutralization efficacy. IQNPA binds to domain IV of PA containing the host cell receptor binding site, while IQNLF recognizes domain I containing the PA binding region in LF. A single 180-g dose of either antibody given to A/J mice 2.5 h before challenge conferred 100% protection against a lethal intraperitoneal spore challenge with 24 50% lethal doses [LD50s] of Sterne and against rechallenge on day 20 with a more aggressive challenge dose of 41 LD50s. Mice treated with either antibody and infected with Sterne developed detectable murine anti-PA and anti-LF immunoglobulin G antibody responses by day 17 that were dependent on which antibody the mice had received. Based on these results, IQNPA and IQNLF act independently during prophylactic anthrax treatment and do not interfere with the establishment of endogenous immunity. is the secretion of a tripartite exotoxin consisting of two enzymatically active subunits: lethal factor (LF) and edema factor Herbacetin (EF). These proteins bind to protective antigen (PA), the cell-binding component, to form lethal toxin (LeTx) and edema toxin, respectively (53). The biological activities of LeTx and edema toxin are analogous to those of other A-B toxin systems (14). PA initially binds to a cell surface receptor, including human capillary morphogenesis protein 2 and tumor endothelial marker 8 (4, 45), and undergoes furin-like mediated cleavage of the N-terminal domain. This event yields an amino-terminal 20-kDa fragment and a carboxyl-terminal 63-kDa activated PA63 protein with exposed LF/EF binding domains. The PA63 conformer assembles to form a ring-shaped heptamer with the capacity to bind up to three copies of LF or EF (22, 31, 32). At this point the toxin Herbacetin complex is endocytosed. Subsequent acidification of the endosome causes the PA63 heptamer to insert into the membrane, forming a transmembrane channel that traffics LF and EF to the cytosol (29). LF endopeptidase activity with the MEK family of signal transduction proteins down-regulates both the innate and acquired immune responses by inhibiting cytokine responses, dendritic cell responses, and B- and T-cell immunity (1, 30). EF, an adenylate Herbacetin cyclase, incapacitates phagocytes and cytokine pathways through cyclic AMP induction and up-regulates the PA63 receptor on target cells (17, 36). Given the central role of the toxins in anthrax pathology, Herbacetin the ability to neutralize their effects is of value at all stages of infection. The credentials of as an aerosolized bioterror agent were confirmed by the 2001 postal attacks in the United States, which resulted in five deaths (20). These events underscored the need for postexposure medical countermeasures that are effective, particularly during middle to advanced stages of infection, when bacteremia and toxemia ensue. Animal studies have previously suggested that early treatment of anthrax is essential since the disease reaches a point when antibiotics are no longer effective due to the accumulation of a lethal level of toxin (48, 49, 56). In order to counteract the limitations of antibiotics, several groups have been pursuing various therapeutic strategies that evoke rapid protection against anthrax by targeting PA, LF, or capsular antigen (7, 18, 21, 23, 28, 33, 35, 37, 46, 59, 63). The most promising approach has been administration of antitoxin antibodies to generate a state of immediate passive immunity. This therapy involves the transfer of serum from an immunized donor or monoclonal antibodies (MAbs) to an exposed or at risk recipient. The efficacy of this treatment has been demonstrated in an anthrax guinea pig challenge model using polyclonal anti-PA serum from immunized guinea pigs (26). A murine MAb specific for LF has also exhibited protective efficacy during experimental LeTx challenge of athymic nude mice (63). One of the major concerns with this therapeutic agent is the immunogenicity of the antibody as a foreign protein. This concern has been partially circumvented by the generation of an affinity-enhanced, humanized, anti-PA MAb that was developed from a murine immunoglobulin G (IgG) (33). More recently, human peripheral blood lymphocytes from immunized humans have been used in Herbacetin hybridomas as progenitors of prophylactic anti-PA antibodies (44, 58). The use of human being IgG eliminates the risk of adverse reactions associated with nonhuman serum and antibodies while the immune system recall response is utilized to create high-affinity toxin-neutralizing antibodies. Here we statement the isolation and.