Submitted to: PLoS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/26/2016
Publication Date: 3/1/2016
Citation: McCaig, W.D., Loving, C.L., Hughes, H.R., Brockmeier, S. 2016. Characterization and vaccine potential of outer membrane vesicles produced by Haemophilus parasuis. PLoS One. 11(3):e0149132.
Interpretive Summary: Haemophilus parasuis is a bacterium that can cause disease and death in pigs, and causes major financial losses to the swine industry. There are hundreds of different types of this bacterium, some of which cause disease and others which do not. There are commercial vaccines that can be given to pigs to protect against the types of Haemophilus that cause disease, but they do not work against every type of Haemophilus that a pig may be exposed to. As bacteria replicate they naturally produce vesicles which are small round objects that have a number of functions and contain pieces of the bacteria. These vesicles have been examined in numerous other bacteria to determine what components are in them and how they contribute to disease. Researchers have taken vesicles from disease causing bacteria and used them as a vaccine to protect against those same bacteria. In this study we have examined vesicles from two different types of Haemophilus, one which causes disease and one which does not. We have determined which components are present in them and compared them in an attempt to highlight the important parts of both the bacteria and the vesicles they create. We have taken cells from pigs and exposed them to these vesicles to determine how the cells will respond to them. Finally, we injected these vesicles into pigs as a vaccine and found that the animals were able to survive infection with a dose of bacteria that would normally kill them. This is the first examination of vesicles produced by this bacterium and highlights their potential use as a vaccine and the important role that they play in causing disease.
Technical Abstract: Haemophilus parasuis is a Gram-negative bacterium that colonizes the upper respiratory tract of swine and is capable of causing a systemic infection, resulting in high morbidity and mortality. H. parasuis isolates display a wide range of virulence and virulence factors are largely unknown. A commercial bacterin is often used to vaccinate swine against H. parasuis, though strain variability and lack of cross-reactivity can make this an ineffective means of protection. Outer membrane vesicles (OMV) are spherical structures naturally released from the membrane of bacteria and OMV are often enriched in toxins, signaling molecules and other bacterial components. Examination of OMV structures has led to identification of virulence factors in a number of bacteria and they have been successfully used as subunit vaccines. We have isolated OMV from both virulent and avirulent strains of H. parasuis, have examined their protein content and assessed their ability to induce an immune response in the host. Vaccination with purified OMV derived from the virulent H. parasuis Nagasaki strain provided protection against challenge with a lethal dose of the bacteria.