Biology subjects

Boucontet, L.

Publications and source records attributed to Boucontet, L..

3 recordsLinked to original sources

bioRxiv2021

Zebrafish larvae as a powerful model to dissect protective innate immunity in response to Legionella pneumophila infection

The zebrafish has become a powerful model organism to study host-pathogen interactions. Here, we developed a zebrafish model of Legionella pneumophila infection to dissect innate immune responses. We show that L. pneumophila cause zebrafish larvae death in a dose dependent manner, and that macrophages are the first line of defence, with neutrophils cooperating to clear the infection. When either macrophages or neutrophils are depleted, these "immunocompromised" larvae become lethally sensitive to L. pneumophila similar to what is known for humans that develop pneumonia. Also as observed in human infections, the adaptor signalling molecule Myd88 is not required to control disease in the larvae. Furthermore, proinflammatory cytokine genes il1{beta} and tnf were upregulated during infection, recapitulating key immune responses seen in human infection. Strikingly, we uncovered a previously undescribed infection phenotype in zebrafish larvae, whereby bloodborne, wild type L. pneumophila invade and grow in the larval yolk region, a phenotype not observed with a type IV secretion system deficient mutant that cannot translocate effectors into its host cell. Thus, zebrafish larva represents an innovative L. pneumophila infection model that that on one hand mimics important aspects of the human immune response to L. pneumophila infection and that on the other hand will allow to elucidate the mechanisms by which type IV secretion effectors allow L. pneumophila to cross membranes and to obtain nutrients from nutrient rich environments.

microbiology↗

bioRxiv2021

NAD kinase controls antibiotic susceptibility and pathogenic potential in Staphylococcus aureus

Nicotinamide adenine dinucleotide phosphate (NADPH) is the primary electron donor for reductive reactions that are essential for the biosynthesis of major cell components in all organisms. Nicotinamide adenine dinucleotide kinase (NADK) is the only enzyme that catalyzes synthesis of NADP(H) from NAD(H). While the enzymatic properties and physiological functions of NADK have been thoroughly studied, the role of NADK in bacterial pathogenesis remains unknown. Here, we used CRISPR interference to knockdown NADK gene expression to address the role of this enzyme in Staphylococcus aureus pathogenic potential. We find that NADK inhibition drastically decreases mortality of zebrafish infected with S. aureus. Further, we show that NADK promotes S. aureus survival in infected macrophages by protecting bacteria from antimicrobial defense mechanisms. Proteome-wide data analysis revealed that production of major virulence associated factors is sustained by NADK. We demonstrate that NADK is required for expression of the quorum-sensing response regulator AgrA, which controls critical S. aureus virulence determinants. These findings support a key role for NADK in bacteria survival within innate immune cells and the host during infection.

microbiology↗

bioRxiv2021

Exploring zebrafish larvae as a COVID-19 model: probable SARS-COV-2 replication in the swim bladder

Animal models are essential to understand COVID-19 pathophysiology and for pre-clinical assessment of drugs and other therapeutic or prophylactic interventions. We explored the small, cheap and transparent zebrafish larva as a potential host for SARS-CoV-2. Bath exposure, as well as microinjection in the coelom, pericardium, brain ventricle, bloodstream, or yolk, did not result in detectable SARS-CoV-2 replication in wild-type larvae. However, when the virus was inoculated in the swim bladder, a modest increase in viral RNA was observed after 24 hours, suggesting a successful infection in some animals. This was confirmed by immunohistochemistry, with cells positive for SARS-CoV-2 nucleoprotein observed in the swim bladder. Several variants of concern were also tested with no evidence of increased infectivity in our model. Low infectivity of SARS-CoV-2 in zebrafish larvae was not due to the host type I interferon response, as comparable viral loads were detected in type I interferon-deficient animals. Mosaic overexpression of human ACE2 was not sufficient to increase SARS-CoV-2 infectivity in zebrafish embryos or in fish cells in vitro. In conclusion, wild-type zebrafish larvae appear mostly non-permissive to SARS-CoV-2, except in the swim bladder, an aerial organ sharing similarities with the mammalian lung.

microbiology↗