Protective Monoclonal Antibodies Against Pseudomonas aeruginosa Derived from B Cells of Cystic Fibrosis Patients

Core Concepts

Monoclonal antibodies derived from PcrV-specific B cells of cystic fibrosis patients exhibit potent anti-Pseudomonas aeruginosa activity in a mouse pneumonia model.

Abstract

The content describes the discovery and characterization of novel monoclonal antibodies (mAbs) targeting the Pseudomonas aeruginosa (PA) virulence factor PcrV, which were derived from B cells of cystic fibrosis (CF) patients.

Key highlights:

• PcrV-specific B cells are enriched in the peripheral blood of CF individuals compared to non-CF controls.
• Single-cell sequencing of PcrV-specific B cells from CF donors enabled the rapid identification of multiple high-affinity anti-PcrV mAbs.
• Several mAbs derived from both naïve and memory B cells of CF donors exhibited robust protection against PA infection in a mouse pneumonia model, matching or exceeding the activity of a previously engineered anti-PcrV mAb.
• This human B cell-derived approach avoids the need for extensive antibody engineering and optimization required for mAbs generated from animal immunization.
• The findings provide new insights into the PA-specific humoral immune response in CF and yield promising therapeutic candidates for treating multidrug-resistant PA infections.

Stats

PcrV-specific B cells made up ≥ 5% of total B cells in 10 out of 14 (71%) CF donors, compared to non-CF controls.
Mice treated with a single, 20 µg intranasal dose of anti-PcrV IgG mAbs from CF donors exhibited an ∼2 log reduction in PA lung burden at 24 hours compared to control.
All 5 anti-PcrV mAbs tested, including 3 derived from memory B cells, achieved significant reductions in PA lung burden in the mouse pneumonia model.

Quotes

"Strikingly, all three CF MBC-derived mAbs including 437 (originally derived from an IgG MBC), 439 (derived from an IgA MBC), and 442 (derived from an IgM MBC) achieved significant reductions in bacterial burden at 24 h when compared to an off-target control mAb or saline alone."
"Our findings employing BCR sequences from multiple isotypes are consistent with contemporaneous work by Simonis et al showing protection in neutropenic mice by 3 anti-PcrV mAbs discovered by single-cell BCR sequencing of IgG-expressing B cells from two CF donors."

Key Insights Distilled From

Monoclonal antibodies derived from B cells in subjects with cystic fibrosis reduce Pseudomonas aeruginosa burden in mice

by Hale,M., Tak... at www.biorxiv.org 04-12-2024

https://www.biorxiv.org/content/10.1101/2024.04.08.588618v1

Deeper Inquiries

What are the potential advantages of using human B cell-derived mAbs over previously developed anti-PcrV antibody candidates for clinical application?

Human B cell-derived monoclonal antibodies (mAbs) present several significant advantages over previously developed anti-PcrV antibody candidates, particularly those derived from murine models. Firstly, human-derived mAbs are less likely to elicit an immune response in patients, reducing the risk of immunogenicity that can lead to adverse effects or diminished therapeutic efficacy. This is crucial for patients with cystic fibrosis (CF), who may already have compromised immune systems. Secondly, the antibodies generated from human B cells are the product of natural immune responses, which means they are more likely to possess optimal binding affinities and functional characteristics tailored to effectively neutralize Pseudomonas aeruginosa (PA). The study highlighted that the mAbs derived from CF patients exhibited robust anti-PA activity, demonstrating their potential for clinical application. Additionally, human mAbs can retain full effector functions, such as complement activation and antibody-dependent cellular cytotoxicity, which are often diminished in engineered murine antibodies. Lastly, the rapid discovery process employed in this study, which utilized single-cell sequencing of B cell receptors (BCRs) from CF patients, allows for the efficient identification of high-affinity mAbs, potentially accelerating the development of effective therapies against multidrug-resistant PA infections.

How might the dynamics and functional characteristics of PcrV-specific B cells in CF patients differ from the general population, and what implications could this have for understanding the endogenous anti-PA immune response?

The dynamics and functional characteristics of PcrV-specific B cells in people with cystic fibrosis (pwCF) are likely distinct from those in the general population due to the chronic nature of PA infections in this group. The study found that pwCF have a higher frequency of PcrV-specific B cells compared to non-CF controls, indicating an enhanced immune response to PA. This expansion of PcrV-specific B cells suggests that pwCF may have a more robust memory B cell (MBC) repertoire, which could be a result of repeated exposure to PA over time. Furthermore, the presence of class-switched antibodies in CF serum and sputum at higher concentrations than in the general population indicates that pwCF are capable of generating effective humoral responses despite the chronic infections. These dynamics imply that the endogenous anti-PA immune response in pwCF is shaped by ongoing antigen exposure, leading to a unique B cell repertoire that may be more adept at producing protective antibodies. Understanding these differences is crucial for developing targeted therapies, as it may reveal specific B cell subsets or antibody characteristics that are particularly effective against PA, informing future vaccine strategies or therapeutic interventions.

Given the diverse PcrV-specific BCR repertoire observed in CF donors, could this approach be leveraged to develop mAb cocktails or bispecific antibodies targeting multiple PA virulence factors to enhance therapeutic breadth and potency?

Yes, the diverse PcrV-specific B cell receptor (BCR) repertoire observed in cystic fibrosis (CF) donors can indeed be leveraged to develop monoclonal antibody (mAb) cocktails or bispecific antibodies targeting multiple virulence factors of Pseudomonas aeruginosa (PA). The study demonstrated that multiple high-affinity anti-PcrV mAbs could be derived from the BCR sequences of CF patients, indicating a rich source of potential therapeutic candidates. By combining different mAbs that target various PA virulence factors, it is possible to create a cocktail that enhances therapeutic breadth and potency, potentially overcoming the challenges posed by PA's intrinsic and acquired antibiotic resistance. Bispecific antibodies could also be engineered to simultaneously bind to PcrV and other critical virulence factors, such as the polysaccharide Psl or other components of the type III secretion system, thereby providing a multifaceted approach to neutralizing PA's pathogenicity. This strategy could improve treatment outcomes by reducing bacterial load more effectively and preventing the emergence of resistant strains, ultimately leading to better management of PA infections in patients with cystic fibrosis.