Karina Ray
Po-Jui Chen
Susan Yun
Diane G. Elliott
Carla M. Conway
Michael Culcutt
Maureen K. Purcell
Timothy J Welch
John Patrick Bellah
Ellie Maureen Dalsky
Justin Blaine Greer
Esteban Soto
John D. Hansen
2021
<div id="abstracts"><div class="core-container"><div>Several<span> </span><i>Francisella</i><span> </span>spp. including<span> </span><i>F. noatunensis</i><span> </span>are regarded as important emerging pathogens of wild and farmed fish. However, very few studies have investigated the virulence factors that allow these bacterial species to be pathogenic in fish. The Francisella Pathogenicity Island (FPI) is a well-described, gene-dense region encoding major virulence factors for the genus<span> </span><i>Francisella.</i><span> </span>PdpA is a member of the pathogenicity determining protein genes encoded by the FPI that are implicated in the ability of the mammalian pathogen,<span> </span><i>F. tularensis</i>, to escape and replicate in infected host cells. Using a<span> </span><i>sacB</i><span> </span>suicide approach, we generated<span> </span><i>pdpA</i><span> </span>knockouts to address the role of PdpA as a virulence factor for<span> </span><i>F. noatunensis</i>. Because polarity can be an issue in gene-dense regions, we generated two different marker-based mutants in opposing polarity (<i>Fno</i>Δ<i>pdpA1</i><span> </span>and Δ<i>pdpA2</i>). Both mutants were attenuated (p<0.0001) in zebrafish challenges and displayed impaired intracellular replication (p<0.05) and cytotoxicity (p<0.05), all of which could be restored to wild-type (WT) levels by complementation for<span> </span><i>Fno</i>Δ<i>pdpA</i>1. Importantly, differences were found for bacterial burden and induction of acute phase and pro-inflammatory genes for<span> </span><i>Fno</i>Δ<i>pdpA</i>1 and Δ<i>pdpA</i>2 compared to WT during acute infection. In addition, neither mutant resulted in significant histopathological changes. Finally, immunization with<span> </span><i>Fno</i>Δ<i>pdpA1</i><span> </span>led to protection (p<0.012) against an acute lethal-dose 40 challenge with WT<span> </span><i>Fno</i><span> </span>in the zebrafish model of infection. Taken together, this study further demonstrates physiological similarities within the genus<span> </span><i>Francisella</i><span> </span>relative to their phylogenetic relationships and the utility of zebrafish for addressing virulence factors for the genus.</div></div></div>
application/pdf
10.1128/IAI.00220-21
en
American Society for Microbiology
Disruption of the Francisella noatunensis orientalis pdpA gene results in virulence attenuation and protection in zebrafish
article