Biology subjects

Rooijakkers, S.

Publications and source records attributed to Rooijakkers, S..

6 recordsLinked to original sources

bioRxiv2026

Mycoplasma immunoglobulin binding protein universally binds human antibodies, thereby reducing Fab arm flexibility and displacing antigens in immune complexes

Mycoplasma immunoglobulin binding (MIB) protein plays a key role in immune evasion across several Mycoplasma species. MIB tightly interacts with the Fab domain of immunoglobulin G, inducing conformational changes that disrupt the antigen-binding site. Here, we reveal that MIB binds strongly and universally to all major isotypes and subclasses of human antibodies and can thus serve as a bait protein to efficiently deplete antibodies from serum. Our results demonstrate strong interactions between MIB and a diverse set of both recombinant monoclonal and endogenous polyclonal antibodies, the latter purified from serum or colostrum. All antibodies, including IgG and IgA monomers, J-chain coupled IgA dimers, and IgM pentamers, consistently bind two copies of MIB per antibody protomer. Using cross-linking mass spectrometry, we pinpoint that antibody-MIB interactions involve conserved regions of the variable and constant antibody domains, independent of isotype. Furthermore, we demonstrate that MIB not only disrupts the Fab-antigen interaction but also restricts Fab flexibility, as visualized by atomic force microscopy. Conversely, MIB does not affect Fc-mediated protein interactions, as exemplified by the successful reconstitution of a 36-subunit immune complex, (IgG)6-(MIB)12-C1q.

biochemistry↗

bioRxiv2023

Antibody-drug conjugates to treat bacterial biofilms

Implant-associated infections remain a grand unmet medical need because they involve biofilms that protect bacteria from the immune system and harbour antibiotic-tolerant persister cells. There is an urgent need for new biofilm-targeting therapies with antimicrobials, to treat these infections via a non-surgical way. In this work, we address this urgent medical need and engineer antibody-drug conjugates (ADC) that kill bacteria in suspension and in biofilms, in vitro and in vivo. The ADC contains an anti-neoplastic drug mitomycin C, which is also a potent antimicrobial against biofilms. While most ADCs are clinically validated as anti-cancer therapeutics where the drug is released after internalisation of the ADC in the target cell, the ADCs designed herein release the conjugated drug without cell entry. This is achieved with a novel mechanism of drug, which likely involves an interaction of ADC with thiols on the bacterial cell surface. ADC targeted towards bacteria were superior by the afforded antimicrobial effects compared to the non-specific counterpart, in suspension and within biofilms, in vitro and in vivo. An implant-associated murine osteomyelitis model was then used to demonstrate the ability of the antibody to reach the infection, and the superior antimicrobial efficacy compared to standard antibiotic treatment in vivo. Our results illustrate the development of ADCs into a new area of application with a significant translational potential.

microbiology↗

bioRxiv2022

Polyfunctional pathogen-specific CD4+ T cells reside in the lungs and tumors of NSCLC patients

Local T cell responses are required for optimal protection of the lungs against airborne pathogens. This localized protection is mediated by various immune cells, including resident memory T cells (TRM). While human lung CD8+ TRM line the epithelium and are enriched for recognition of respiratory viruses, we found CD4+ TRM to exhibit more heterogeneous localization patterns, surrounding airways, forming clusters in the lung parenchyma, and lining the epithelium. This heterogeneity was also reflected functionally, as lung CD4+ TRM were enriched for recognition of diverse classes of respiratory pathogens. Upon stimulation, lung CD4+ TRM expressed different polyfunctional cytokine profiles depending on the pathogen recognized. CD4+ TRM responding to respiratory viruses and bacteria were biased for production of IFN-{gamma} and IL-17, respectively. Strikingly, pathogen-specific CD4+ TRM also represent a significant fraction in NSCLC tumors that remained polyfunctional despite high PD-1 expression. These findings are not only important for vaccine design, but also provide a rationale for reinvigorating anti-tumor immunity through triggering of polyfunctional pathogen-specific CD4+ tumor infiltrating lymphocytes.

immunology↗

bioRxiv2022

Promoting Fc-Fc interactions between anti-capsular antibodies provides strong complement-dependent immune protection against Streptococcus pneumoniae

Streptococcus pneumoniae is the leading cause of community-acquired pneumonia and an important cause of childhood mortality. Despite the introduction of successful vaccines, the global spread of both non-vaccine serotypes and antibiotic-resistant strains reinforce the development of alternative therapies against this pathogen. One possible route is the development of monoclonal antibodies (mAbs) that induce killing of bacteria via the immune system. Here we investigate whether mAbs can be used to induce killing of pneumococcal serotypes for which the current vaccines show unsuccessful protection. Our study demonstrates that when human mAbs against pneumococcal capsule polysaccharides (CPS) have a poor capacity to induce complement activation, a critical process for immune protection against pneumococci, their activity can be strongly improved by hexamerization-enhancing mutations. Our data indicate that anti-capsular antibodies may have a low capacity to form higher-order oligomers (IgG hexamers) that are needed to recruit complement component C1. Indeed, specific point mutations in the IgG-Fc domain that strengthen hexamerization strongly enhance C1 recruitment and downstream complement activation on encapsulated pneumococci. Specifically, hexamerization-enhancing mutations E430G or E345K in CPS6-IgG strongly potentiate complement activation on S. pneumoniae strains that express capsular serotype 6 (CPS6), and the highly invasive serotype 19A strain. Furthermore, these mutations improve complement activation via mAbs recognizing CPS3 and CPS8 strains. Importantly, hexamer-enhancing mutations enable mAbs to induce strong phagocytosis and intracellular killing by human neutrophils. Finally, passive immunization with CPS6-IgG1-E345K protected mice from developing severe pneumonia. Altogether, this work provides an important proof-of-concept for future optimization of antibody therapies against encapsulated bacteria.

microbiology↗

bioRxiv2021

Molecular features underlying Pseudomonas aeruginosa persistence in human plasma

Pseudomonas aeruginosa, an opportunistic Gram-negative pathogen, is a leading cause of bacteremia with a high mortality rate. We recently reported that P. aeruginosa forms a persister-like sub-population of evaders in human plasma and blood. However, the molecular mechanisms underlying the formation of evaders remained unknown. Here, using a gain-of-function genetic screen, we examined the molecular determinants of P. aeruginosa persistence in plasma. We found that, among other factors, ATP and biotin availability greatly influence bacterial survival in plasma; mutants in pur and bio genes display higher tolerance and persistence, respectively. Electron microscopy combined with energy-dispersive X-ray spectroscopy (EDX) revealed the formation of polyphosphate granules upon incubation in plasma in several clinical strains, implying the bacterial response to a low-energy stress signal. Indeed, mutants with transposon insertions in ppk genes were eliminated in the plasma. Analysis of several steps of the complement cascade and exposure to an outer-membrane-impermeable drug, nisin, suggested that the mutants impede membrane attack complex (MAC) activity per se. Through this study, we shed light on P. aeruginosa response to the plasma conditions and discovered the multifactorial origin of bacterial resilience to MAC that provides a comprehensive picture of the complex interplay between P. aeruginosa and the human complement system. Author summaryPersistence of bacterial pathogens is a main cause of treatment failure and establishment of chronic bacterial infection. Despite innate immune responses, some bacteria may persist in human blood and plasma. Here we used a genome-wide screen to investigate the molecular determinants influencing Pseudomonas aeruginosa persistence in human plasma facing the complement system. Alongside a multifactorial strategy, we found intracellular levels of ATP and biotin to significantly influence bacterial capacity to deal with membrane attack complex (MAC)-dependent killing. These results underline the need to understand the complex interplay between bacterial pathogens and the human immune system when seeking to develop efficient antibacterial strategies.

microbiology↗

bioRxiv2020

In vitro evolution of colistin resistance in the Klebsiella pneumoniae complex follows multiple evolutionary trajectories with variable effects on fitness and virulence characteristics.

The increasing prevalence of multidrug-resistant Gram-negative opportunistic pathogens, including Klebsiella pneumoniae, has led to a resurgence in the use of colistin as a last-resort drug. Colistin is a cationic lipopeptide antibiotic that selectively acts on Gram-negative bacteria through electrostatic interactions with anionic phosphate groups of the lipid A moiety of lipopolysaccharides (LPS). Colistin resistance in K. pneumoniae is mediated through loss of these phosphate groups, or modification with cationic groups (e.g. 4-amino-4-deoxy-L-arabinose (L-Ara4N), or phosphoethanolamine), but also hydroxylation of acyl-groups of lipid A. Here, we study the in vitro evolutionary trajectories towards colistin resistance in clinical K. pneumoniae complex strains (three K. pneumoniae sensu stricto strains and one K. variicola subsp. variicola strain) and their impact on fitness and virulence characteristics. Through population sequencing during the in vitro evolution experiment, we found that resistance develops through a combination of single nucleotide polymorphisms (SNPs), insertion and deletions (indels), and the integration of insertion sequence (IS) elements, affecting genes associated with LPS biosynthesis and modification, and capsule structures. The development of colistin resistance decreased the maximum growth rate of one K. pneumoniae sensu stricto strain, but not in the other three K. pneumoniae sensu lato strains. Colistin-resistant strains had lipid A modified through hydroxylation, palmitoylation, and L-Ara4N addition. Colistin-resistant K. pneumoniae sensu stricto strains exhibited cross-resistance to LL-37, in contrast to the K. variicola subsp. variicola strain that did not change in susceptibility to LL-37. Virulence, as determined in a Caenorhabditis elegans survival assay, was higher in two colistin-resistant strains. Our study suggests that nosocomial K. pneumoniae complex strains can rapidly develop colistin resistance de novo through diverse evolutionary trajectories upon exposure to colistin. This effectively shortens the lifespan of this last-resort antibiotic for the treatment of infections with multidrug-resistant Klebsiella. Author summaryBacteria that frequently cause infections in hospitalised patients are becoming increasingly resistant to antibiotics. Colistin is a positively charged antibiotic that is used for the treatment of infections with multidrug-resistant Gram-negative bacteria. Colistin acts by specifically interacting with the negatively charged LPS molecule in the outer membrane of Gram-negative bacteria. Colistin resistance is mostly mediated through modification of LPS to reduce its negative charge. Here, we use a laboratory evolution experiment to show that strains belonging to the Klebsiella pneumoniae complex, a common cause of multidrug-resistant hospital-acquired infections, can rapidly accumulate mutations that reduce the negative charge of LPS without an appreciable loss of fitness. Colistin resistance can lead to cross-resistance to an antimicrobial peptide of the human innate immune system, but can increase susceptibility to serum, and virulence in a nematode model. These findings show that extensively resistant K. pneumoniae complex strains may rapidly develop resistance to the last-resort antibiotic colistin via different evolutionary trajectories, while retaining their ability to cause infections.

microbiology↗