Antigenic and phenotypic modifications of Yersinia pestis under calcium and glucose concentrations simulating the mammalian bloodstream environment

Abstract

To study the possible mechanism of extracellular resistance to phagocytes developed by Yersinia pestis in the early stage of plague infection, the behaviour of two Y. pestis strains, the vaccine EV-76 and fully virulent 231 (LD 50 , 10 c.f.u.), was studied in-depth after cultivation in vitro at the host temperature in conditions simulating the bloodstream environment of mammals. For this, two standard basal media supplemented with calcium and glucose in appropriate concentrations were employed: Hottinger broth, routinely used for growth of Y. pestis in vitro, and RPMI 1640, simulating human extracellular fluid. Although both media permitted Y. pestis to achieve the resistant state, RPMI enabled significantly higher bacterial proliferation and increased modifications in the production of the principal surface antigens that affect the relevant phenotype characteristics. In general, our results indicate that the Y. pestis bacteria in the resistant state do not produce speciesspecific antigens, i.e. fraction 1 or F1, 'murine' toxin or Ymt, plasminogen activator (Pla) and any surface-specific polysaccharides, resulting in unmasking of the cross-reactive epitopes of lipid A in reduced Y. pestis lipopolysaccharide. This may produce mimicry by Y. pestis of some human tissue and blood cell components, with no immune response and inflammation at the site of infection at the early stage, which enables Y. pestis to survive, extensively multiply and spread into the circulation.

Deletion of the Braun Lipoprotein-Encoding Gene and Altering the Function of Lipopolysaccharide Attenuate the Plague Bacterium

“…In addition, Y. pestis EV ⌬lpxM showed a lower growth rate in vitro but replicated and remained at the site of inoculation significantly longer than the parental EV NIIEG strain (39). Therefore, the better immunogenicity of Y. pestis EV ⌬lpxM was most likely due to these pleiotropic effects, including the dampening of the host innate immune response as well as enhanced bacterial persistence, leading to the activation of adaptive immunity (39,63).…”

Pleiotropic effects of the lpxM mutation in Yersinia pestis resulting in modification of the biosynthesis of major immunoreactive antigens

“…To identify the ability of the cells of Y. pestis EV NIIEG and its Δ lpxM derivative to form a capsule-like substance, the bacteria were analysed by electron microscopy as described elsewhere [39]. For this purpose, bacterial samples were examined with a JEOL model JSM-U3 microscope.…”

“…For this purpose, bacterial samples were examined with a JEOL model JSM-U3 microscope. Test samples of bacterial suspensions were placed on carbon-coated collodion grids followed by the treatment and negative staining as described [39]. …”

“…(MAb-F1) as reported previously [39]. Also, the production of the F1 antigen was determined by an indirect hemagglutination test with polyclonal antibodies specific to the Y. pestis capsular fraction F1 (PAb-F1) (The Institute for Microbiology of the Ministry of Defense, Kirov, Russia) using a routine technique [40].…”

Physiological Levels of Glucose Induce Membrane Vesicle Secretion and Affect the Lipid and Protein Composition of Yersinia pestis Cell Surfaces

“…Previously it was suggested that the bloodstream environment induces bacterial resistance to phagocytosis by suppression of Y. pestis-specific antigens (42). We hypothesized that glucose may induce phenomena previously unrecognized in Y. pestis, such as the observed changes in lipid and protein compositions and/or the induction of the MV secretion system.…”