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Generation of Discriminative Human Monoclonal Antibodies from Rare Antigen-specific B Cells Circulating in Blood
Published on: February 6, 2018
Isolation of highly active monoclonal antibodies against multiresistant gram-positive bacteria
Friederike S Rossmann1, Diana Laverde2, Andrea Kropec2
1Department of Medicine, Division of Infectious Diseases, University Hospital, Freiburg, Germany; Faculty of Biology, Albert-Ludwigs-University, Freiburg, Germany; Department of Pediatrics, Dr. von Hauner Children's Hospital, Ludwig-Maximilians University, Munich, Germany; German Center of Infection Research (DZIF), Partnersite Munich, Germany.
Abstract:
Multiresistant nosocomial pathogens often cause life-threatening infections that are sometimes untreatable with currently available antibiotics. Staphylococci and enterococci are the predominant Gram-positive species associated with hospital-acquired infections. These infections often lead to extended hospital stay and excess mortality. In this study, a panel of fully human monoclonal antibodies was isolated from a healthy individual by selection of B-cells producing antibodies with high opsonic killing against E. faecalis 12030. Variable domains (VH and VL) of these immunoglobulin genes were amplified by PCR and cloned into an eukaryotic expression vector containing the constant domains of a human IgG1 molecule and the human lambda constant domain. These constructs were transfected into CHO cells and culture supernatants were collected and tested by opsonophagocytic assay against E. faecalis and S. aureus strains (including MRSA). At concentrations of 600 pg/ml, opsonic killing was between 40% and 70% against all strains tested. Monoclonal antibodies were also evaluated in a mouse sepsis model (using S. aureus LAC and E. faecium), a mouse peritonitis model (using S. aureus Newman and LAC) and a rat endocarditis model (using E. faecalis 12030) and were shown to provide protection in all models at a concentration of 4 μg/kg per animal. Here we present a method to produce fully human IgG1 monoclonal antibodies that are opsonic in vitro and protective in vivo against several multiresistant Gram-positive bacteria. The monoclonal antibodies presented in this study are significantly more effective compared to another monoclonal antibody currently in clinical trials.
Insights
Fully human monoclonal antibodies show significant opsonic killing and in vivo protection against multiresistant Gram-positive bacteria, offering a promising new therapeutic strategy for hospital-acquired infections.
Area of Science:
- Immunology
- Infectious Diseases
- Biotechnology
Background:
- Multiresistant nosocomial pathogens, particularly Gram-positive bacteria like Staphylococci and Enterococci, cause severe hospital-acquired infections.
- These infections are often untreatable with current antibiotics, leading to increased mortality and prolonged hospital stays.
- There is a critical need for novel therapeutic strategies to combat these resistant infections.
Purpose of the Study:
- To develop fully human monoclonal antibodies with potent opsonic and protective activity against multiresistant Gram-positive bacteria.
- To establish a method for producing these therapeutic antibodies for potential clinical use.
- To compare the efficacy of these novel antibodies against existing clinical candidates.
Main Methods:
- Isolation of B-cells producing high-opsonic killing antibodies against *E. faecalis*.
- Amplification and cloning of antibody variable domains (VH and VL) into an IgG1 expression vector.
- Transfection into CHO cells, followed by supernatant collection and testing via opsonophagocytic assays and in vivo animal models (sepsis, peritonitis, endocarditis).
Main Results:
- Monoclonal antibodies demonstrated 40-70% opsonic killing against *E. faecalis* and *S. aureus* (including MRSA) at 600 pg/ml.
- Significant protection was observed in mouse sepsis and peritonitis models, and a rat endocarditis model at 4 μg/kg.
- The developed antibodies showed superior efficacy compared to a monoclonal antibody currently in clinical trials.
Conclusions:
- A novel method for producing fully human IgG1 monoclonal antibodies with in vitro and in vivo efficacy against multiresistant Gram-positive bacteria has been established.
- These antibodies represent a promising therapeutic approach for life-threatening hospital-acquired infections.
- The developed monoclonal antibodies exhibit enhanced effectiveness compared to existing therapeutic options in clinical development.
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