Host–pathogen interaction | EPFL Graph Search

The host–pathogen interaction is defined as how microbes or viruses sustain themselves within host organisms on a molecular, cellular, organismal or population level. This term is most commonly used to refer to disease-causing microorganisms although they may not cause illness in all hosts. Because of this, the definition has been expanded to how known pathogens survive within their host, whether they cause disease or not. On the molecular and cellular level, microbes can infect the host and divide rapidly, causing disease by being there and causing a homeostatic imbalance in the body, or by secreting toxins which cause symptoms to appear. Viruses can also infect the host with virulent DNA, which can affect normal cell processes (transcription, translation, etc.), protein folding, or evading the immune response. Pathogenicity Pathogen history One of the first pathogens observed by scientists was Vibrio cholerae, described in detail by Filippo Pacini in 1854.

Quantitative Single-Cell Analysis of Host-Pathogen Interactions

Matthieu Jean-Hubert Delincé

During infection, microbial pathogens encounter phagocytic cells of the host innate immune system, such as macrophages and neutrophils. These encounters typically lead to uptake and killing of the bacteria by the host cell or, conversely, parasitization of the host cell by the bacteria. Microscopic analysis of these host-microbe interactions is complicated by the fact that phagocytic cells are motile and tend to stray out of the field of view. Most host-pathogen studies have therefore been undertaken at the population level. However, the success of many pathogens likely lies in their ability to generate heterogeneity within the population, facilitating adaptation to every host micro-environment and to environmental perturbations (such as application of an antibiotic). We believe that studying host-pathogen interactions at the single-cell level can reveal not only new mechanisms of pathogenesis but also why current treatments are not always successful. This thesis presents a novel microfluidic device for the long-term co-culturing of phagocytic cells and bacteria within spatially confining microchambers. Each device is patterned with thousands of microchambers, permitting high-throughput fluorescence timelapse microscopy of host-microbe interactions at single-cell resolution. We demonstrate the utility of this approach by co-culturing an established host-cell model, Dictyostelium discoideum, with the extracellular pathogen Klebsiella pneumoniae. We observed that K. pneumoniae is readily taken up and killed by D. discoideum but some events can take ten times as long as others. The capsule, a polysaccharide layer present at the surface at the bacterial cell wall, reduces the phagocytosis efficiency by 1.5 fold, but does not influence the killing time. The opportunistic human pathogen Mycobacterium marinum was then used to study intracellular bacterial virulence. As expected, bacteria could infect host cells, replicate inside, and eventually lyse them. However, surprisingly, in the majority of the infections, the bacteria were actually released from the host, with no apparent harm to either the host or the bacteria. Less frequently, bacteria were even seen being killed. The timing of these events was highly heterogeneous, ranging from a couple of hours to several days. In summary, the tools presented in this thesis provide a new and simple approach for following individual host-microbe interactions at high spatiotemporal resolution from the onset to the end of infections. This work unveiled that the timing and outcome of host-microbe interactions are unexpectedly heterogeneous, which may have important consequences for the bacterial pathogenesis and ultimately for the development of future treatment of microbial infections.

EPFL2016

Patchy Amphiphilic Dendrimers Bind Adenovirus and Control Its Host Interactions and in Vivo Distribution

Weina Liu, Francesco Stellacci

The surface of proteins is heterogeneous with sophisticated but precise hydrophobic and hydrophilic patches, which is essential for their diverse biological functions. To emulate such distinct surface patterns on macromolecules, we used rigid spherical synthetic dendrimers (polyphenylene dendrimers) to provide controlled amphiphilic surface patches with molecular precision. We identified an,. I optimal spatial arrangement of these patches on certain dendrimers that enabled their interaction with human adenovirus 5 (Ads). Patchy dendrimers bound to the surface of Ads formed a synthetic polymer corona that greatly altered various host interactions of Ads as well as in vivo distribution. The dendrimer corona (1) improved the ability of Ad5-derived gene transfer vectors to transduce cells deficient for the primary Ad5 cell membrane receptor and (2) modulated the binding of Ads to blood coagulation factor X, one of the most critical virus host interactions in the bloodstream. It significantly enhanced the transduction efficiency of Ad5 while also protecting it from neutralization by natural antibodies and the complement system in human whole blood. Ads with a synthetic dendrimer corona revealed profoundly altered in vivo distribution, improved transduction of heart, and dampened vector sequestration by liver and spleen. We propose the design of bioactive polymers that bind protein surfaces solely based on their amphiphilic surface patches and protect against a naturally occurring protein corona, which is highly attractive to improve Ad5-based in vivo gene therapy applications.

2019

Cecropins contribute to Drosophila host defense against a subset of fungal and Gram-negative bacterial infection

Alexia Laurie Carboni, Mark Austin Hanson, Bruno Lemaitre

Cecropins are small helical secreted peptides with antimicrobial activity that are widely distributed among insects. Genes encoding Cecropins are strongly induced upon infection, pointing to their role in host defense. In Drosophila, four cecropin genes clustered in the genome (CecA1, CecA2, CecB, and CecC) are expressed upon infection downstream of the Toll and Imd pathways. In this study, we generated a short deletion Delta Cec(A-C) removing the whole cecropin locus. Using the Delta Cec(A-C) deficiency alone or in combination with other antimicrobial peptide (AMP) mutations, we addressed the function of Cecropins in the systemic immune response. Delta Cec(A-C) flies were viable and resisted challenge with various microbes as wild-type. However, removing Delta Cec(A-C) in flies already lacking 10 other AMP genes revealed a role for Cecropins in defense against Gram-negative bacteria and fungi. Measurements of pathogen loads confirm that Cecropins contribute to the control of certain Gram-negative bacteria, notably Enterobacter cloacae and Providencia heimbachae. Collectively, our work provides the first genetic demonstration of a role for Cecropins in insect host defense and confirms their in vivo activity primarily against Gram-negative bacteria and fungi. Generation of a fly line (Delta AMP14) that lacks 14 immune inducible AMPs provides a powerful tool to address the function of these immune effectors in host-pathogen interactions and beyond.

OXFORD UNIV PRESS INC2022

Quantitative Single-Cell Analysis of Host-Pathogen Interactions

Matthieu Jean-Hubert Delincé

EPFL2016