Immunogenicity and toxicity of lipopolysaccharide from Francisella tularensis LVS

Abstract

Lipopolysaccharide (LPS) from the live vaccine strain of Francisella tularensis (F. tularensis LVS) was isolated and purified. The LPS did not stimulate lymphocytes from previously tularaemia‐vaccinated individuals or lymphocytes from nonprimed individuals. However, serum antibodies from tularaemia vaccines reacted with the LPS whereas virtually no reactivity was found with antibodies from individuals not exposed to F. tularensis LVS. Antibodies of immunoglobulin class M displayed the antibody reactivity predominantly. The LPS failed to induce the mononuclear cell‐derived cytokine interleukin‐1 and only low levels of tumour necrosis factor were detected. Furthermore, no LPS endotoxin properties were found in galactosamine‐treated mice or in the Limulus amoebocyte lysate assay. From these results it can be concluded that F. tularensis LVS possesses a lipopolysaccharide‐like molecule, which does not exhibit properties of a classical endotoxin.

Characterization of the O antigen gene cluster and structural analysis of the O antigen of Francisella tularensis subsp. tularensis

“…holarctica (Dreisbach et al, 2000). It is reported that the LPS is less toxic than other Gram-negative LPS (Ancuta et al, 1996;Sandstrom et al, 1992) and that its O antigen contains the rare sugars 2-acetamido-2,6-dideoxy-D-glucose (QuiNAc) and 4,6-dideoxy-4-formamido-D-glucose (Qui4NFm) and two moles of 2-acetamido-2-deoxy-D-galacturonamide (GalNAcAN), to give the repeat structure 4-AE-GalNAcAN-1,4 -AE-GalNAcAN -1,3 -â-QuiNAc -1,2 -â-Qui4NFm (Vinogradov et al, 1991). The repeat structure is similar to those found in the O antigens of Pseudomonas aeruginosa O6 and Shigella dysenteriae type 7 (Knirel et al, 1988;Vinogradov et al, 1987).…”

Purified Lipopolysaccharide fromFrancisella tularensisLive Vaccine Strain (LVS) Induces Protective Immunity against LVS Infection That Requires B Cells and Gamma Interferon

“…More recent reports indicated that purified LVS LPS was not endotoxic in D-galactosamine-sensitized mice (37) and failed to activate Limulus amoebocyte lysate (37). Further, LVS LPS also failed to stimulate human monocytes or peripheral blood lymphocytes to proliferate, produce tumor necrosis factor alpha (TNF-␣), or produce interleukin-1 (IL-1) (37). Similarly, mouse peritoneal exudate macrophages treated with LVS LPS did not produce TNF-␣ or nitric oxide, and there was no increase in surface immunoglobulin expression by a mouse pre-B-cell line in response to LVS LPS (1).…”

“…No traditional endotoxin has been associated with virulent F. tularensis (23). More recent reports indicated that purified LVS LPS was not endotoxic in D-galactosamine-sensitized mice (37) and failed to activate Limulus amoebocyte lysate (37). Further, LVS LPS also failed to stimulate human monocytes or peripheral blood lymphocytes to proliferate, produce tumor necrosis factor alpha (TNF-␣), or produce interleukin-1 (IL-1) (37).…”

“…Francisella has apparently evolved the ability to undergo phase variation of LPS expression, such that F. tularensis normally expresses the "nontoxic" chemotype of LPS but occasionally switches to expression of a stimulatory chemotype of LPS that is characteristic of the closely related bacterium Francisella novicida (6); this indicates that regulated variation between LPSs of different biological properties confers a survival advantage on the bacterium. Further, detection of antibodies to Francisella LPS has been useful in diagnosis of human disease from natural infection (37,42) as well as in demonstrating successful vaccination with LVS (44), indicating that Francisella LPS is immunogenic. Mice given repeated large doses of LVS LPS were protected against lethal LVS infection (19).…”

Francisella tularensis Suppresses the Proinflammatory Response of Endothelial Cells via the Endothelial Protein C Receptor

“…These pathways lead to secretion of chemokines and upregulation of adhesion molecules that recruit neutrophils, monocytes, and other immune cells to the site of infection. The LPS of F. tularensis, however, is atypical and incites few proinflammatory changes in murine and human leukocytes or human endothelial cells (23)(24)(25)(26). Moreover, live F. tularensis stimulates HUVECs to secrete only low amounts of the chemokine CCL2 compared with the killed bacterium or Escherichia coli (27).…”