Peptidoglycan-Free Bacterial Ghosts Confer Enhanced Protection against Yersinia pestis Infection.

Svetlana V Dentovskaya,Tat’Yana V Gapel’Chenkova,Sergei A Ivanov,Alexandra S Trunyakova,Galina M Titareva,Anastasia S Vagaiskaya,Elizaveta M Mazurina,Andrey P Anisimov,Sergei A Kotov,Vladimir N Gerasimov,Mikhail E Platonov,Rima Z Shaikhutdinova,Ekaterina A Krasil’Nikova,Tat’Yana I Kombarova,Vladimir N Uversky

doi:10.3390/vaccines10010051

Abstract

To develop a modern plague vaccine, we used hypo-endotoxic Yersinia pestis bacterial ghosts (BGs) with combinations of genes encoding the bacteriophage ɸX174 lysis-mediating protein E and/or holin-endolysin systems from λ or L-413C phages. Expression of the protein E gene resulted in the BGs that retained the shape of the original bacterium. Co-expression of this gene with genes coding for holin-endolysin system of the phage L-413C caused formation of structures resembling collapsed sacs. Such structures, which have lost their rigidity, were also formed as a result of the expression of only the L-413C holin-endolysin genes. A similar holin-endolysin system from phage λ containing mutated holin gene S and intact genes R-Rz coding for the endolysins caused generation of mixtures of BGs that had (i) practically preserved and (ii) completely lost their original rigidity. The addition of protein E to the work of this system shifted the equilibrium in the mixture towards the collapsed sacs. The collapse of the structure of BGs can be explained by endolysis of peptidoglycan sacculi. Immunizations of laboratory animals with the variants of BGs followed by infection with a wild-type Y. pestis strain showed that bacterial envelopes protected only cavies. BGs with maximally hydrolyzed peptidoglycan had a greater protectivity compared to BGs with a preserved peptidoglycan skeleton.

Highlights

Plague, an infamous zoonotic bacterial infection caused by Yersinia pestis, has claimed more than 200 million human lives
The λ phage holin-endolysin system is composed of S, R, and Rz/Rz1 genes, coding for holin, endolysin and accessory proteins, respectively, which are involved in bacterial cell wall degradation
Unlike the single phage ΦX174 self-sufficient lysis gene E, which product, independently of other genes, discontinues synthesis of the cell wall compartments locally at the site of formation of the transmembrane tunnel, the expression of endolysin is operated by holin, a small hydrophobic protein, which forms in the host cytoplasmic membrane oligomeric pores, allowing endolysin accumulated in the cytoplasm to penetrate through the pores in the inner membrane into the periplasm, where endolysin hydrolyzes all peptidoglycan available to it

Summary

Introduction

An infamous zoonotic bacterial infection caused by Yersinia pestis, has claimed more than 200 million human lives. The killed and live plague vaccines of the first generation were successfully used to save tens of millions of people, but they had a number of shortcomings. Being highly protective for mice infected with Y. pestis typical strains, they are less protective for challenged guinea pigs and monkeys [5]. The water-insoluble “residual” antigen from yersiniae bacterial cell walls initiating a classical T cell-modulated state of cellular immunity reliably protects guinea pigs and monkeys, but is ineffective for mice [5,6,7,8]

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