Introduction on Monoclonal Antibodies

Monoclonal antibodies (mAbs) are a group of antibodies produced by identical clones of B lymphocytes against a particular antigen. mAbs are identical in several properties such as protein sequence, antigen-binding site region, binding affinity for their targets, and identical downstream functional effects. These characteristics of mAbs highlight their differences with the polyclonal antibodies which have heterogenous activities and recognize different epitopes on an antigen. Murine mAbs was the first generation of mAbs developed by hybridoma technology however, because of their murine origin, they can trigger the anti-mouse antibody response in the host which could accelerate mAb clearance and undesirable allergic reactions upon repeated administration. This issue was resolved by developing engineering methods toward producing less immunologic chimeric or humanized antibodies. mAbs applications have become a novel way of targeting antigens in a wide variety of diseases such as autoimmunity, malignancies, and asthma. In addition, high specificity and high affinity binding properties of mAbs make them effective biological reagents in immunodiagnostic assays. They can be used in diagnosis of infectious diseases and detection of certain antigens or in serological assessments for detection of antibodies against a certain antigen. This chapter summarizes the general properties of mAbs, their production processes, and their important diagnostic and therapeutic applications.

Protective Effect of Anti-Phosphatidylserine Antibody in a Guinea Pig Model of Advanced Hemorrhagic Arenavirus Infection

Objective:Host derived markers on virally infected cells or virions may provide targets for the generation of antiviral agents. Recently, we identified phosphatidylserine (PS) as a host marker of virions and virally-infected cells.Methods and Materials:Under normal physiological conditions, PS is maintained on the inner leaflet of the plasma membrane facing the cytosol. Following viral infection, activation or pre-apoptotic changes cause PS to become externalized. We have previously shown that bavituximab, a chimeric human-mouse antibody that binds PS complexed with β2-glycoprotein I (β2GP1), protected rodents against lethal Pichinde virus and cytomegalovirus infections.Results:Here, we determined the antiviral activity of a fully human monoclonal antibody, PGN632, that directly binds to PS. Treatment with PGN632 protected 20% of guinea pigs with advanced infections of the hemorrhagic arenavirus, Pichinde, from death. Combining PGN632 with ribavirin improved the antiviral activity of both agents, such that the combination rescued 50% of animals from death.Conclusion:The major mechanisms of action of PGN632 appear to be opsonization of virus and antibody-dependent cellular cytotoxicity of virally-infected cells. PS-targeting agents may have utility in the treatment of viral diseases.

Evaluation of tumor marker cancer antigen 72-4 (CA 72-4) in the monitoring of metastatic or recurrent tumors of the gastrointestinal tract, lung, breast, and ovaries.

263 Background: In management of metastatic and recurrent cancers, measuring response is a constant challenge. CA72-4 is a tumor marker (TM) that has been found elevated in a variety of human adenocarcinomas, with reported sensitivities of up 50% and overall specificity of over 95%. Using the DRG TM-CA72-4 assay, we quantified the abnormality rate of TM CA72-4 compared with current FDA-approved TM in various cancers. Methods: We conducted a prospective, single center study by enrolling 96 patients between March 2013 and August 2016 with various de novo or previously diagnosed locally advanced, unresectable and/or metastatic cancers known to express CA72-4. Quantification of CA72-4 was performed according to manufacturer’s instructions using the DRG TM-CA72-4 ELISA kit, which was developed by DRG International (Germany) utilizing the CC-49 monoclonal mouse antibody directed against an epitope on the CA72-4 antigen. Positivity was calculated as greater than A) 0.8 U/mL or B) 4.0 U/mL based on systematic review of prior studies. Results: The positivity rates based on different cut-off points (0.8 U/mL vs 4 U/mL) and their corresponding FDA approved tumor markers are shown in the Table. Conclusions: Positivity rates of CA72-4 varied based on different assay cut-off levels with the highest positivity noted in the pancreatic, ovarian and colorectal carcinomas indicating a potential role for disease monitoring. [Table: see text]