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Updated: Sep 1, 2025
A Neonatal Imaging Model of Gram-Negative Bacterial Sepsis
Published on: August 12, 2020
Monoclonal antibodies effectively potentiate complement activation and phagocytosis of Staphylococcus epidermidis in
Lisanne de Vor1, Coco R Beudeker2, Anne Flier1
1Department of Medical Microbiology, University Medical Center Utrecht, Utrecht, Netherlands.
Insights
Monoclonal antibodies targeting Staphylococcus epidermidis show promise in preventing neonatal bloodstream infections. These antibodies, when combined with complement activation, significantly enhance bacterial killing by neutrophils in neonatal plasma.
Area of Science:
- Immunology
- Neonatal Medicine
- Infectious Diseases
Background:
- Central line-associated bloodstream infections (CLABSI) caused by Staphylococcus epidermidis are a significant threat to neonates due to their underdeveloped immune systems.
- Previous attempts using pooled intravenous immunoglobulins (IVIG) for prevention have yielded limited success, highlighting the need for novel therapeutic strategies.
Purpose of the Study:
- To investigate the efficacy of specific monoclonal antibodies (mAbs) against Staphylococcus epidermidis in promoting phagocytic killing by human neutrophils.
- To assess the role of complement activation and potential enhancements through Fc-mutations in mAb-mediated bacterial clearance.
- To evaluate the performance of these mAbs in neonatal plasma conditions.
Main Methods:
- Nine human IgG1 monoclonal antibodies targeting Staphylococcus surface components were generated.
- Binding affinities to Staphylococcus epidermidis strains were assessed.
- Phagocytic killing assays were performed using opsonized bacteria (with or without complement) and human neutrophils, including experiments in neonatal plasma.
Main Results:
- Three mAbs (rF1, CR5133, CR6453) demonstrated strong binding to Staphylococcus epidermidis, with CR5133 and CR6453 effective against most clinical isolates from neonatal sepsis.
- Complement activation was essential for efficient phagocytosis, and Fc-mutations enhanced this process.
- Neonatal plasma exhibited comparable classical pathway complement activity to adult plasma, and mAbs significantly boosted Staphylococcus epidermidis phagocytosis in this setting.
Conclusions:
- Monoclonal antibodies targeting Staphylococcus epidermidis can effectively enhance neutrophil-mediated phagocytosis and killing, particularly when complement is activated.
- Fc-mutations can optimize mAb function for improved therapeutic potential.
- These findings support the development of anti-Staphylococcus epidermidis mAbs as a promising prophylactic strategy against neonatal CLABSI.
Abstract:
Central line associated bloodstream infections (CLABSI) with Staphylococcus epidermidis are a major cause of morbidity in neonates, who have an increased risk of infection because of their immature immune system. As especially preterm neonates suffer from antibody deficiency, clinical studies into preventive therapies have thus far focused on antibody supplementation with pooled intravenous immunoglobulins from healthy donors (IVIG) but with little success. Here we study the potential of monoclonal antibodies (mAbs) against S. epidermidis to induce phagocytic killing by human neutrophils. Nine different mAbs recognizing Staphylococcal surface components were cloned and expressed as human IgG1s. In binding assays, clones rF1, CR5133 and CR6453 showed the strongest binding to S. epidermidis ATCC14990 and CR5133 and CR6453 bound the majority of clinical isolates from neonatal sepsis (19 out of 20). To study the immune-activating potential of rF1, CR5133 and CR6453, bacteria were opsonized with mAbs in the presence or absence of complement. We observed that activation of the complement system is essential to induce efficient phagocytosis of S. epidermidis. Complement activation and phagocytic killing could be enhanced by Fc-mutations that improve IgG1 hexamerization on cellular surfaces. Finally, we studied the ability of the mAbs to activate complement in r-Hirudin neonatal plasma conditions. We show that classical pathway complement activity in plasma isolated from neonatal cord blood is comparable to adult levels. Furthermore, mAbs could greatly enhance phagocytosis of S. epidermidis in neonatal plasma. Altogether, our findings provide insights that are crucial for optimizing anti-S. epidermidis mAbs as prophylactic agents for neonatal CLABSI.
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