Efficacy of a <i>Pseudomonas aeruginosa</i> serogroup O9 vaccine

Abstract

There are currently no approved vaccines against the opportunistic pathogen <i>Pseudomonas aeruginosa</i>. Among vaccine targets, the lipopolysaccharide (LPS) O antigen of <i>P. aeruginosa</i> is the most immunodominant protective candidate. There are 20 different O antigens composed of different repeat sugar structures conferring serogroup specificity, and 10 are found most frequently in infection. Thus, one approach to combat infection by <i>P. aeruginosa</i> could be to generate immunity with a vaccine cocktail that includes all these serogroups. Serogroup O9 is 1 of the 10 serogroups commonly found in infection, but it has never been developed into a vaccine, due in part to the acid-labile nature of the O9 polysaccharide. Our laboratory has previously shown that intranasal administration of an attenuated <i>Salmonella</i> strain expressing the <i>P. aeruginosa</i> serogroup O11 LPS O antigen was effective in clearing bacteria and preventing mortality in mice following intranasal challenge with serogroup O11 <i>P. aeruginosa</i>. Consequently, we set out to develop a <i>P. aeruginosa</i> serogroup O9 vaccine using a similar approach. Here, we show that <i>Salmonella</i> expressing serogroup O9 triggered an antibody-mediated immune response following intranasal administration to mice and that it conferred protection from <i>P. aeruginosa</i> serogroup O9 in a murine model of acute pneumonia.