Outer Membrane Protein X (Ail) Contributes to Yersinia pestis Virulence in Pneumonic Plague and Its Activity Is Dependent on the Lipopolysaccharide Core Length

Abstract

Yersinia pestis, the causative agent of plague, is one of the most virulent microorganisms known. The outer membrane protein X (OmpX) in Y. pestis KIM is required for efficient bacterial adherence to and internalization by cultured HEp-2 cells and confers resistance to human serum. Here, we tested the contribution of OmpX to disease progression in the fully virulent Y. pestis CO92 strain by engineering a deletion mutant and comparing its ability in mediating pneumonic plague to that of the wild type in two animal models. The deletion of OmpX delayed the time to death up to 48 h in a mouse model and completely attenuated virulence in a rat model of disease. All rats challenged with 1 ؋ 10 8 CFU of the ompX mutant survived, compared to the 50% lethal dose (LD 50 ) of 1.2 ؋ 10 3 CFU for the wild-type strain. Because murine serum is not bactericidal for the ompX mutant, the mechanism underlying the delay in time to death in mice was attributed to loss of adhesion/internalization properties but not serum resistance. The rat model, which is most similar to humans, highlighted the critical role of serum resistance in disease. To resolve conflicting evidence for the role of Y. pestis lipopolysaccharide (LPS) and OmpX in serum resistance, ompX was cloned into Escherichia coli D21 and three isogenic derivatives engineered to have progressively truncated LPS core saccharides. OmpX-mediated serum resistance, adhesiveness, and invasiveness, although dependent on LPS core length, displayed these functions in E. coli, independently of other Yersinia proteins and/or LPS. Also, autoaggregation was required for efficient OmpX-mediated adhesiveness and internalization but not serum resistance.

Absence of YbeY RNase compromises the growth and enhances the virulence plasmid gene expression of Yersinia enterocolitica O:3

“…RNA-sequencing, quantitative proteomics and RT-qPCR revealed unanimously a reduction in the level of Ail in the mutant strain, which could explain the observed impairment in adhesion. This is in accordance with previous findings showing an ail mutant leads to a severe reduction in adhesion (Felek & Krukonis, 2009;Kolodziejek et al, 2010). In spite of the decrease in adhesion, the ybeY bacteria that had adhered were still able to enter the cells at the WT level, suggesting that the process of invasion itself was not affected.…”

Outer Membrane Proteins Ail and OmpF of Yersinia pestis Are Involved in the Adsorption of T7-Related Bacteriophage Yep-phi

“…For example, a drastic decrease of the concentration of OmpF has been observed in E. coli LPS mutants (45). Ail-mediated resistance to human serum depends on the LPS core (39), and changes in the LPS structure may influence the Ail conformation and specific activity (38). However, whether the receptor functions of Ail and OmpF are related to the LPS core remains unknown.…”

“…OmpF is often regarded as a classical porin, which is present in large quan- tities, and is also required as a receptor by several phages of E. coli (31,36,37). Ail protein is essential for Y. pestis to resist complement-mediated killing, and Ail-mediated resistance to human serum depends on the LPS core (38,39). However, the function of Ail in phage receptors has yet to be fully explained.…”

Recent Advancement in the Development of Vaccines Against Y. pestis - A Potential Agent of Bioterrorism

“…This capsule enhances resistance to engulfment by both macrophages and neutrophils, probably by preventing interactions of receptors that could facilitate uptake of the pathogen (Du et al, 2002). It was also observed that Y. pestis produces a less-acylated (tetra-acylated) lipid A at 37 °C, which results in poor induction of host tolllike receptor (TLR) 4-mediated innate immune responses and ultimately poor activation of human macrophages (Kawahara et al, 2002;Kolodziejek et al, 2010). When Y. pestis KIM1001, which expresses a poorly TLR4-stimulating LPS, was modified to strongly induce TLR4, it became avirulent (Montminy et al, 2006).…”

“…Genes for additonal virulence proteins such as, Ail (attachment invasion locus, also designated as OmpX), plasminogen activator protease (Pla), and pH 6 antigen (Psa) have been deleted in an effort to generate effective live attenuated vaccine strains (Felek et al, 2010). In a pneumonic plague model, animals infected with a ompX mutant of Y. pestis CO92 survived for two days longer than those infected with the parent strain (Kolodziejek et al, 2010). Moreover, Δcaf1 mutants and ΔpsaA mutants exhibited decreased virulence in a murine infection model (Weening et al, 2011).…”