Construction of a Live-Attenuated Vaccine Strain of Yersinia pestis EV76-B-SHUΔpla and Evaluation of Its Protection Efficacy in a Mouse Model by Aerosolized Intratracheal Inoculation

Abstract

Plague, which is caused by Yersinia pestis, is one of the most dangerous infectious diseases. No FDA-approved vaccine against plague is available for human use at present. To improve the immune safety of Y. pestis EV76 based live attenuated vaccine and to explore the feasibility of aerosolized intratracheal inoculation (i.t.) route for vaccine delivery, a plasminogen activator protease (pla) gene deletion mutant of the attenuated Y. pestis strain EV76-B-SHU was constructed, and its residual virulence and protective efficacy were evaluated in a mouse model via aerosolized intratracheal inoculation (i.t.) or via subcutaneous injection (s.c.). The residual virulence of EV76-B-SHU pla was significantly reduced compared to that of the parental strain EV76-B-SHU following i.t. and s.c. infection. The EV76-B-SHU pla induced higher levels of mucosal antibody sIgA in the bronchoalveolar lavage fluid of mice immunized by i.t. but not by s.c.. Moreover, after lethal challenge with Y. pestis biovar Microtus strain 201 (avirulent in humans), the protective efficacy and bacterial clearance ability of the EV76-B-SHU pla-i.t. group were comparable to those of the EV76-B-SHU pla-s.c. and EV76-B-SHU immunized groups. Thus, the EV76-B-SHU pla represents an excellent live-attenuated vaccine candidate against pneumonic plague and aerosolized i.t. represents a promising immunization route in mouse model.

Complete Protection Against Yersinia pestis in BALB/c Mouse Model Elicited by Immunization With Inhalable Formulations of rF1-V10 Fusion Protein via Aerosolized Intratracheal Inoculation

“…We recently demonstrated the liquid formulation of EV76-B-SHUΔ pla delivered by i.t. route represents an excellent live-attenuated vaccine candidate against pneumonic plague ( 54 ), but it is likely unsuitable for preparation of powder by SFD, which will affect survivability and overall fitness of the live bacteria. In the current study, we evaluated the protection efficacy of three subunit vaccines administrated with three different formulations via i.t.…”

“…The i.t. immunization was performed using a Dry Powder Insufflator for powder inoculation and a MicroSprayer Aerosolizer for reconstituted powder or liquid inoculation following previously described methods ( 54 ). Group details are shown in Table 1 (five experimental groups per protein, five negative controls, and two blank controls).…”

“…The lungs, spleens, and livers of these mice were harvested individually and approximately 100 mg of each organ homogenized in 800 µl PBS. Samples of 50 µl of homogenate were diluted serially in PBS, and 10 µl dilutions were plated onto blood agar plates for bacterial counting as previously described ( 54 ).…”

Intratracheal inoculation of AHc vaccine induces protection against aerosolized botulinum neurotoxin A challenge in mice

“…immunization with AHc vaccines against aerosolized BoNT/A intoxication, the three AHc vaccine formulations were used to immunize mice via the i.t. or the s.c. route for three times at 3-week intervals 29,36 as previously described. The immunization scheme and groups are shown in Fig.…”

Yersinia Outer Membrane Vesicles as Potential Vaccine Candidates in Protecting against Plague

“…As for the two immunodominant antigens of Y. pestis , subunit vaccines based on F1 (Caf1), the fraction 1 pilus antigen, and V (LcrV), a protein at the tip of type III secretion needles, have shown promising results in several animal models [ 3 , 4 , 5 ]. However, they mainly induce an immune response, which, as a rule, in the majority of animal models is significantly inferior in protective potency and duration of post-infectious immunity (in surviving animals) and even post-vaccination immunity induced by live attenuated bacteria in different mammalian species [ 6 , 7 , 8 , 9 , 10 ]. Only in mice subunit preparations containing F1 antigen can induce a degree of protection no less than that induced by the live plague vaccine.…”