Abstract
BackgroundPasteurella pneumotropica is a ubiquitous bacterium that is frequently isolated from laboratory rodents and causes various clinical symptoms in immunodeficient animals. Currently two RTX toxins, PnxIA and PnxIIA, which are similar to hemolysin-like high-molecular-weight exoproteins are known in this species. In this study, we identified and analyzed a further RTX toxin named PnxIIIA and the corresponding type I secretion system.ResultsThe RTX exoprotein, PnxIIIA, contains only a few copies of the RTX repeat-like sequence and 3 large repeat sequences that are partially similar to the outer membrane protein found in several prokaryotes. Recombinant PnxIIIA protein (rPnxIIIA) was cytotoxic toward J774A.1 mouse macrophage cells, whereas cytotoxicity was attenuated by the addition of anti-CD11a monoclonal antibody. rPnxIIIA could bind to extracellular matrices (ECMs) and cause hemagglutination of sheep erythrocytes. Binding was dependent on the 3 large repeat sequences in PnxIIIA. Protein interaction analyses indicated that PnxIIIA is mainly localized in the outer membrane of P. pneumotropica ATCC 35149 in a self-assembled oligomeric form. PnxIIIA is less cytotoxic to J774A.1 cells than PnxIA and PnxIIA.ConclusionsThe results implicate that PnxIIIA is located on the cell surface and participates in adhesion to ECMs and enhanced hemagglutination in the rodent pathogen P. pneumotropica.
Highlights
Pasteurella pneumotropica is a ubiquitous bacterium that is frequently isolated from laboratory rodents and causes various clinical symptoms in immunodeficient animals
Identification of the third gene encoding an repeat in structural toxin (RTX) protein A previous study revealed that P. pneumotropica carries 2 genes encoding hemolysin-like proteins that are similar to the RTX toxins PnxIA and PnxIIA [13]
The sequence of the inserts was similar to that of the glycine-rich regions in pnxIIA; the detailed sequence indicated the existence of an additional gene that encodes a protein similar to the RTX toxin
Summary
Pasteurella pneumotropica is a ubiquitous bacterium that is frequently isolated from laboratory rodents and causes various clinical symptoms in immunodeficient animals. Pasteurella pneumotropica is a Gram-negative rod-shaped bacterium that is frequently isolated from the upper respiratory tract of laboratory rodents. This bacterium is a major causative agent of opportunistic infection in rodents, and almost all infected immunocompetent rodents exhibit unapparent infection. An earlier study reported that coinfection by P. pneumotropica and Mycoplasma pulmonis causes pneumonia in specific pathogenfree mice [1]. A recent study reported that P. pneumotropica infection disturbs the inflammation responses in immunocompetent mice [2]. P. pneumotropica infection leads to various serious diseases such as lethal pneumonia and sepsis. It is it is important to clarify the virulence factors and pathogenicity of P. pneumotropica
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