Salmonella Typhimurium strain expressing OprF‐OprI protects mice against fatal infection by Pseudomonas aeruginosa

Abstract

Pseudomonas aeruginosa poses a major threat to human health and to the mink industry. Thus, development of vaccines that elicit robust humoral and cellular immunity against P. aeruginosa is greatly needed. In this study, a recombinant attenuated Salmonella vaccine (RASV) that expresses the outer membrane proteins fusion OprF 190-342 -OprI 21-83 (F1I2) from P. aeruginosa was constructed and the potency of this vaccine candidate assessed by measuring F1I2-specific humoral immune responses upon vaccination through s.c. or oral routes. S.C. administration achieved higher serum IgG titers and IgA titers in the intestine and induced stronger F1I2-specific IgG and IgA titers in lung homogenate than did oral administration, which resulted in low IgG titers and no local IgA production. High titers of IFN-g, IL-4, and T-lymphocyte subsets induced a mixed Th1/Th2 response in mice immunized s.c., indicating elicitation of cellular immunity. Importantly, when immunized mice were challenged with P. aeruginosa by the intranasal route 30 days after the initial immunization, s.c. vaccination achieved 77.78% protection, in contrast to 41.18% via oral administration and 66.67% via Escherichia coli-expressed F1I2 (His-F1I2) vaccination. These results indicate that s.c. vaccination provides a better protective response against P. aeruginosa infection than do oral administration and the His-F1I2 vaccine.Key words outer membrane protein, Pseudomonas aeruginosa, Salmonella Typhimurium, subcutaneous vaccination.Pseudomonas aeruginosa is a major cause of pulmonary infection, causing cystic fibrosis-and non-cystic fibrosisrelated bronchiectasis and chronic obstructive pulmonary disease. It is also a common pathogen responsible for hospital-acquired infections in burn, transplant, cancer and intensive care unit patients (1). Various animals, including dogs, dairy cows, horses, mink and foxes, are believed to be susceptible to P. aeruginosa (2). In particular, P. aeruginosa has been a major cause of hemorrhagic pneumonia in mink for the last 50 years, resulting in serious losses in the Chinese mink industry (2, 3). Although there have been considerable advances in antimicrobial therapy for the treatment and control of P. aeruginosa infection, undesirable adverse effects remain a persistent problem, primarily because of the natural resistance of this pathogen and its formidable ability to acquire resistance to multiple antimicrobial agents by various mechanisms. Therefore, measures to effectively contain P. aeruginosa infection are urgently needed. List of Abbreviations: APC, antigen-presenting cell; DAP, 2,6-diaminopimelic acid; DTH, delayed-type hypersensitivity; F1, part of outer membrane proteins F ) of Pseudomonas aeruginosa; I2, part of outer membrane proteins I (OprI 21-83 ) of Pseudomonas aeruginosa; PQ, Salmonella Typhimurium LH430 with asd deleted; RASV, recombinant attenuated Salmonella vaccine.

Understanding Pseudomonas aeruginosa–Host Interactions: The Ongoing Quest for an Efficacious Vaccine

“…Preclinical studies [330,331] and a phase I-II clinical trial [332] involving Salmonella species for the nasal or oral delivery of Pseudomonas OprF or OprI, induced IgG and IgA antibodies. In contrast, in murine models, subcutaneous vaccination with an S. Typhimurium LH430 expressing OprF-OprI achieved the highest levels of protection and specific immunoglobulin titres than oral immunisation [333]. Importantly, a recent study, where an attenuated S. Typhimurium expressing S. enterica type III secretion effector protein, SseJ, and the P. aeruginosa PcrV elicited detectable levels of antigen-specific IgG in all mice, reduced bacterial loads in the spleens and lungs and the levels of proinflammatory cytokines (TNF-α and IL-6) and most of the vaccinated mice survived.…”

Pushing beyond the Envelope: the Potential Roles of OprF in Pseudomonas aeruginosa Biofilm Formation and Pathogenicity

“…Due to the highly immunogenic nature of OprF, numerous studies have utilized the porin in pursuit of a P. aeruginosa vaccine (85,86). Many recent publications involving the administration of chimeric OprF fusion proteins have demonstrated acquired immunity to P. aeruginosa can be achieved in mammals (87)(88)(89)(90)(91). Hassan et al demonstrated that a recombinant trivalent OprF-OprI-flagellin vaccine significantly reduced mortality resulting from acute pneumonia in mice infected with mucoid and nonmucoid strains of P. aeruginosa (89).…”

Pseudomonas aeruginosa: Recent Advances in Vaccine Development

“…One clinical study in healthy volunteers found oral or intranasal administration of live attenuated Salmonella expressing OprF-OprI antigens led to a significant rise in specific IgA and IgG in the lower airways [ 111 ]. Consequently, further preclinical studies in mice using OprF-OprI [ 112 ] and one study using components of the T3SS [ 113 ] enhanced survival, reduced bacterial growth, and led to overall lower levels of pro-inflammatory cytokines.…”