Enervated Reside Yersinia Pestis Conservation Vaccine Shear Against Fatal Y. pestis Inflammation

Christopher Bozue^*
*Correspondence: Christopher Bozue, Department of Bacteriology, United States Army Medical Research Institute of Infectious Diseases, Fort Detrick, MD 21702, USA, Email:

Introduction

The first plague vaccines were developed in the late nineteenth century and consisted of killed whole Yersinia pestis cells. Later, an immunogenic and less reactogenic vaccine containing a formalin-killed suspension of virulent plague bacilli was developed and licenced (Plague Vaccine U.S.P., also known as the Cutter vaccine). It was routinely administered to military personnel stationed in Vietnam as well as other individuals, such as field personnel working in plagueendemic areas who were exposed to rats and fleas, and laboratory personnel working with Y. pestis. Although it was effective in preventing or alleviating bubonic disease, as evidenced by the low incidence of plague among military personnel serving in Vietnam, animal data suggested that it may not protect against pneumonic plague. Moreover, The F1 capsular antigen was the only major protective antigen in these vaccines. Such vaccines are ineffective against genetically engineered or naturally occurring F1-negative strains, which frequently retain virulence despite capsule loss [1].

F1-V, a fusion protein of F1 and LcrV, the low calcium response virulence protein (V), a key immunogen and anti-host factor, is a human plague vaccine candidate currently in clinical trials. V is required for the immunomodulatory Yersinia outer proteins (Yops), effector proteins translocated into host cells by the type three secretion system (T3SS), and it stimulates the production of immunosuppressive cytokines. The F1-V vaccine has been shown to be effective in mice and some nonhuman primate species, but not all. As a result, a more potent plague In large animal models, a vaccine that can induce an enhanced antibody and cell-mediated immune response may be required. Furthermore, F1-V's protection against virulent F1-negative strains is entirely dependent on the V antigen component. Because there is evidence of V heterogeneity within Yersinia species, naturally occurring or engineered strains harbouring altered V antigens have the potential to overcome F1-V induced immunity. They were transferred to wire mesh cages and placed in a wholebody aerosol chamber inside a BSL-3 laboratory's class three biological safety cabinet. Mice were exposed to Y. pestis strain CO92 aerosols generated by a three-jet collison nebulizer. Samples were collected from the all-glass impinger (AGI) vessel and analysed using CFU calculations to determine the Y. pestis inhaled dose [2].

Description

Mice were given aerosolized (pneumonic) or SC (bubonic) challenge doses of virulent Y. pestis prepared as previously described. Bacteria were isolated from tryptose blood agar (TBA) slants for the bubonic plague challenge. Mice exposed via SC were inoculated with 0.2 mL volumes of the suspension in Kphos. Colonies from freshly inoculated TBA slants were suspended in HIBX and incubated for approximately 24 hours at 28-30°C. For the pneumonic plague challenge, the cultures were centrifuged and suspended in HIB medium (no xylose) to the concentration yielding the number of LD₅₀ doses indicated in the tables. Aerosolized bacteria were exposed to as previously described. In brief, mice were Semi-quantitative endpoint ELISA was used to determine immunoglobulin (Ig) IgG, IgG1, and IgG2a antibody responses to the live vaccines using sera from vaccinated BALB/c mice, as previously described [3].

The sera were collected as terminal blood collections from axillary vessels and titrated against several capture antigens: F1 protein, V protein, the F1-V recombinant fusion protein, and -radiation inactivated whole cells of Y. pestis strains CO92 and C12 grown at 30°C (24 h) or 30°C for 21 h followed by a switch to 37°C and incubation for an additional three The F1 and V antigens, as well as the F1-V fusion protein vaccine construct (BEI resources; Manassas, VA, USA), were diluted in 0.1 M carbonate buffer, pH 7. 9.5, to a concentration of 2 g/mL, while inactivated Y. pestis CO92 or C12 whole cells were plated on 96- well Immulon 2HB plates at a concentration of 10 g/mL. (ThermoFisher, Grand Island, NY, USA). Plates were stored at 4°C overnight before being washed, blocked, and processed as previously described. The serum was diluted twice in triplicate, and the results are reported as the geometric mean (Geo Mean) and geometric standard error (GSE) of the reciprocal of the highest dilution yielding a mean OD of at least 0.1 1 SD at 450 nm with a reference filter [4].

Antibody titers less than 50 were considered negative. In addition to live plague vaccines derived from Y. pestis, candidate vaccines have included recombinant and attenuated strains of Salmonella, Yersinia pseudotuberculosis, and other bacteria. Recently, Y. pseudotuberculosis strains modified to express the Y. pestis F1 capsule have been developed and tested. Although Y. pseudotuberculosis is genetically very similar to Y. pestis, only vaccines derived from Y. pestis would be guaranteed to contain the full complement of genetically identical antigens. Y. pseudotuberculosis vaccines also do not produce plasmid encoded proteins and virulence factors such as plasminogen activator (pla) and mouse toxin phospholipase D (ymt); and some Y. pseudotuberculosis strains differ from Y. pestis in their T3SS and encoded effector proteins.

Moreover, Y. Pseudotuberculosis vaccines are frequently administered intragastrically to animals, which increases the possibility of an incorrect or harmful delivery (when compared to a parental route). Our goal is to create next-generation live vaccines that address the potential threat posed by emerging and genetically engineered Y. pestis strains. The initial focus has been on confirming and optimising some of the most promising existing vaccine candidates in terms of safety, immunogenicity, and efficacy. In mouse models of bubonic and pneumonic plague, we tested a panel of Y. pestis vaccine strains for the down-selection of a potential candidate vaccine(s) [5].

Conclusion

In conclusion, our findings support the feasibility of live plague vaccines. Novel candidate attenuated strains of Y. pestis with full protection against bubonic and pneumonic plague caused by the virulent CO92 strain of Y. pestis were identified. The findings of this study encourage further research into developing live vaccines that are optimally protective against lethal plague caused by a wide variety of virulent strains of Y. pestis.

References

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