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Bispecific monoclonal antibody complexes facilitate erythrocyte binding and liver clearance of a prototype
R P Taylor1, E N Martin, M L Reinagel
1Department of Biochemistry, University of Virginia School of Medicine, Charlottesville 22908, USA.
Abstract:
We used Anger camera imaging in a monkey model to investigate the organ localization of a prototype particulate pathogen, 131I-labeled bacteriophage phi X174, after it was bound to the primate erythrocyte complement receptor and then cleared from the circulation. This 131I-labeled phi X174 was infused into the circulation of an immunized monkey, and the nascently formed immune complexes showed rapid and quantitative binding to erythrocytes via the immune adherence reaction (complement-mediated binding). Alternatively, phi X174 was infused into the circulation of a naive animal, and then cross-linked bispecific mAb complexes (heteropolymers, anti-CR1 x anti-phi X174) were infused into the circulation. The infused heteropolymers also facilitated rapid and quantitative binding of phi X174 to erythrocytes. In both cases, after a short lag period, the erythrocyte-bound phi X174 was rapidly cleared from the circulation, and the vast majority of the radiolabel was cleared to the liver, with a small amount clearing to the spleen. Further liver imaging confirmed that within 24 h most of the bacteriophage previously cleared to the liver via the heteropolymer system was phagocytosed and destroyed. The findings in this model system provide additional evidence for the potential utility of heteropolymers to facilitate the safe and rapid clearance of blood-borne pathogens as a potential treatment for infectious diseases.
Insights
Researchers used a monkey model to track a pathogen cleared by immune complexes. Heteropolymers rapidly cleared the pathogen to the liver for destruction, showing potential for treating blood-borne infections.
Area of Science:
- Immunology
- Virology
- Medical Imaging
Background:
- Blood-borne pathogens pose significant infectious disease threats.
- Current treatments may have limitations in rapid pathogen clearance.
- Immune adherence via complement receptors is a natural clearance mechanism.
Purpose of the Study:
- To investigate the organ localization and clearance of a model pathogen, 131I-labeled bacteriophage phi X174.
- To evaluate the efficacy of heteropolymers in facilitating pathogen binding to erythrocytes and subsequent clearance.
- To assess the role of the erythrocyte complement receptor 1 (CR1) in this process.
Main Methods:
- Utilized Anger camera imaging in a monkey model.
- Administered 131I-labeled bacteriophage phi X174 to immunized and naive monkeys.
- Infused cross-linked bispecific monoclonal antibody (mAb) complexes (heteropolymers) targeting CR1 and phi X174.
- Monitored radiolabel distribution and clearance from circulation.
- Performed liver imaging to confirm pathogen destruction.
Main Results:
- Both immune adherence and heteropolymer systems led to rapid, quantitative binding of phi X174 to erythrocytes.
- Erythrocyte-bound phi X174 was cleared from circulation, with the majority of radiolabel directed to the liver and a smaller portion to the spleen.
- Liver imaging confirmed phagocytosis and destruction of the bacteriophage within 24 hours after heteropolymer administration.
- The primate erythrocyte complement receptor played a crucial role in mediating binding.
Conclusions:
- Heteropolymers effectively facilitate the binding of blood-borne pathogens to erythrocytes via complement receptors.
- This system promotes rapid clearance of pathogens to the liver for subsequent destruction.
- Heteropolymer-mediated clearance represents a promising strategy for the treatment of infectious diseases.