The unique Legionella longbeachae capsule favors intracellular replication and immune evasion

Schmidt, S.; Mondino, S.; Gomez-Valero, L.; Escoll, P.; Mascarenhas, D. P.; Goncalves, A.; Rusniok, C.; Sachse, M.; Moya-Nilges, M.; Fontaine, T.; Zamboni, D. S.; Buchrieser, C.

doi:10.1101/2023.11.22.568341

bioRxiv · 10.1101/2023.11.22.568341

The unique Legionella longbeachae capsule favors intracellular replication and immune evasion

Schmidt, S.·Mondino, S.·Gomez-Valero, L.·Escoll, P.·Mascarenhas, D. P.·Goncalves, A.·Rusniok, C.·Sachse, M.·Moya-Nilges, M.·Fontaine, T.·Zamboni, D. S.·Buchrieser, C.

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Abstract

Legionella longbeachae and Legionella pneumophila cause Legionnaires disease despite species-specific differences in environmental niches, disease epidemiology, and genomic content. Here, we characterized a new L. longbeachae virulence factor, a capsule that is expressed in post-exponential growth phase as shown by electron microscopy. Analysis of the capsule composition via HLPC revealed the presence of a highly anionic polysaccharide absent in a capsule mutant. The capsule is crucial for replication and virulence in vivo in a mouse model of infection and in the natural host Acanthamoeba castellanii. It has anti-phagocytic function when encountering innate immune cells, it is involved in a low cytokine responses in mice and in human monocyte derived macrophages and helps to dampen the innate immune response. The L. longbeachae capsule is a novel virulence factor, unique among known Legionella species, that aids L. longbeachae to survive in specific niches and partly confers L. longbeachae its unique infection characteristics.

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Schmidt, S., Mondino, S., Gomez-Valero, L., Escoll, P., Mascarenhas, D. P., Goncalves, A., Rusniok, C., Sachse, M., Moya-Nilges, M., Fontaine, T., Zamboni, D. S., Buchrieser, C.. 2023-11-22. The unique Legionella longbeachae capsule favors intracellular replication and immune evasion. https://doi.org/10.1101/2023.11.22.568341

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