Mucosal Vaccination with a Multivalent, Live-Attenuated Vaccine Induces Multifactorial Immunity against Pseudomonas aeruginosa Acute Lung Infection

Abstract

Many animal studies investigating adaptive immune effectors important for protection against Pseudomonas aeruginosa have implicated opsonic antibody to the antigenically variable lipopolysaccharide (LPS) O antigens as a primary effector. However, active and passive vaccination of humans against these antigens has not shown clinical efficacy. We hypothesized that optimal immunity would require inducing multiple immune effectors targeting multiple bacterial antigens. Therefore, we evaluated a multivalent live-attenuated mucosal vaccination strategy in a murine model of acute P. aeruginosa pneumonia to assess the contributions to protective efficacy of various bacterial antigens and host immune effectors. Vaccines combining 3 or 4 attenuated strains having different LPS serogroups were associated with the highest protective efficacy compared to vaccines with fewer components. Levels of opsonophagocytic antibodies, which were directed not only to the LPS O antigens but also to the LPS core and surface proteins, correlated with protective immunity. The multivalent liveattenuated vaccines overcame prior problems involving immunologic interference in the development of O-antigen-specific antibody responses when closely related O antigens were combined in multivalent vaccines. Antibodies to the LPS core were associated with in vitro killing and in vivo protection against strains with O antigens not expressed by the vaccine strains, whereas antibodies to the LPS core and surface proteins augmented the contribution of O-antigen-specific antibodies elicited by vaccine strains containing a homologous O antigen. Local CD4 T cells in the lung also contributed to vaccine-based protection when opsonophagocytic antibodies to the challenge strain were absent. Thus, multivalent live-attenuated vaccines elicit multifactorial protective immunity to P. aeruginosa lung infections.Pseudomonas aeruginosa lung infections cause substantial morbidity and mortality in humans, manifesting as acute lifethreatening infection, often with bacteremia, in hospitalized and/or immunocompromised patients or as chronic localized lung infection in patients with cystic fibrosis (CF). In hospitalacquired lung infections, which are most commonly ventilatorassociated pneumonias, P. aeruginosa is the leading Gramnegative causative bacterial agent (31). In these infections, the crude mortality rate associated with the bacterium is higher than that due to other bacterial etiologies (30). Despite the widespread and significant impact of P. aeruginosa infections, along with the increasing rates of antibiotic treatment failure due to drug resistance (33), vaccines and immunotherapeutic agents for the disease are still in the early stages of preclinical and clinical development (7).In animal studies, lipopolysaccharide (LPS) O antigens of P. aeruginosa induce potent serogroup-specific protection (i.e., protection against P. aeruginosa strains within the same LPS O-antigen serogroup) (23, 24). However, even within a serogroup there are structural, and hence antige...

Pseudomonas aeruginosa Outer Membrane Vesicles Modulate Host Immune Responses by Targeting the Toll-Like Receptor 4 Signaling Pathway

“…Therefore, the activation of the host immune response elicited by P. aeruginosa OMVs is dependent primarily on LPS via the TLR4 signaling pathway but requires an intact membrane struc- Our study provides further evidence that development of a pseudomonal vaccine based on OMVs of P. aeruginosa is a promising approach. Vaccines that effectively prevent P. aeruginosa pulmonary infections could be very useful, and previous studies suggested that LPS is an influential effector in the development of vaccines in mice (20)(21)(22)51). Ramphal et al also showed that Pseudomonas LPS is not a key virulence factor in acute pneumonia and thus can be used as an adjuvant to trigger a prominent proinflammatory response and effectively defend the lung from P. aeruginosa infection (52).…”

Deletion of Braun Lipoprotein and Plasminogen-Activating Protease-Encoding Genes Attenuates Yersinia pestis in Mouse Models of Bubonic and Pneumonic Plague

“…We have shown that the ⌬lpp ⌬msbB mutant was more attenuated than the single mutants (i.e., the ⌬lpp or ⌬msbB mutant) alone in a mouse model of pneumonic plague and that it generated cell-mediated immune responses (43). On the other hand, studies have also implicated opsonic antibodies to the antigenically variable LPS O antigens as primary immune effectors against Pseudomonas aeruginosa-associated acute lung infection (59,60). Therefore, fine-tuning of attenuation and the immunogenicity is a key to the development of a successful live-attenuated vaccine.…”

Vaccine Immunity to Coccidioidomycosis Occurs by Early Activation of Three Signal Pathways of T Helper Cell Response (Th1, Th2, and Th17)

“…Live vaccines typically generate optimal protection against infectious agents by stimulation of multiple immune effectors that target a broad spectrum of antigenic molecules of the pathogen (18). Immunization of C57BL/6 mice with a previously described live, attenuated "⌬T" vaccine strain of Coccidioides has been shown to induce protection against pulmonary coccidioidal infection based on early reduction of parasitic cell number and containment of the organism (43).…”