Jeremy Ma

Measurement of bactericidal/permeability-increasing protein in human body fluids by sandwich ELISA.

A sensitive sandwich ELISA has been developed to measure levels of native bactericidal/permeability-increasing protein (BPI) as well as two recombinant forms of BPI (rBPI and rBPI23) in human body fluids. The linear range for the rBPI and rBPI23 standard curves were 100-6000 pg/ml and 25-800 pg/ml respectively. Recovery of different concentrations of rBPI spiked into pooled human plasma samples averaged 83% and ranged from 65% at 300 ng/ml to 97% at 3 ng/ml. Recovery of rBPI23 averaged 56% and ranged from 30% at 0.5 ng/ml to 90% at 50,000 ng/ml. Because LBP is present in normal human plasma and shares sequence homology with BPI, the effects of rLBP on the BPI ELISA were also evaluated. Under standard assay conditions, rLBP caused minimal interference with BPI detection. At 100 micrograms/ml, rLBP generated a signal equivalent to 3 ng/ml of rBPI and 0.6 ng/ml of rBPI23. Matched serum and plasma samples were collected from 20 healthy adults to measure endogenous levels of BPI. The range of BPI concentrations was < 0.2-2.1 ng/ml in plasma and 4.9-72.1 ng/ml in serum. Western blot analysis indicated that the BPI ELISA immunoreactivity in plasma and serum correlated with the presence of a protein doublet (M(r) approximately 60,000), which comigrated with native BPI extracted from human neutrophils. These data demonstrate that low levels of holo-BPI are present in plasma, and suggest that additional quantities of BPI were released from neutrophils during the process of coagulation.

Development of XPA067.06, a potent high affinity human anti-gastrin monoclonal antibody

The peptide hormone gastrin is a key factor in regulation of gastric acid secretion. It has also been implicated in the development or maintenance of various types of cancer, such as pancreatic and stomach carcinoma. Inhibition of gastrin activity has potential for therapeutic use as a suppressor of acid secretion as well as an inhibitor of gastrin-responsive tumors. XPA067.06 is an affinity matured, 30 pM fully human anti-gastrin monoclonal antibody that was generated. The antibody was tested in a mouse gastric pH model to determine its effect on acid secretion. In this model, animals were treated with human gastrin, XPA067.06, and H2R or M1 receptor antagonists. Gastric fluid was collected and acid output was measured as a function of pH. XPA067.06 was shown to significantly inhibit gastrin-17-stimulated acid output for at least 48h. These results demonstrate that XPA067.06 effectively binds and neutralizes human gastrin-17 in vivo with rapid onset and prolonged duration of efficacy.