Outer membranes of a lipopolysaccharide-protein complex (LPS-17 kDa protein) as chemical tularemia vaccines.

Immunisation with outer membranes of Francisella tularensis induced an efficient protection in guinea pigs against challenge with the virulent strains 503 or 144/713 (type B biovar holarctica), both clinical isolates, and prevented the development of typical signs of infection in hamadryads (baboons), challenged with the virulent strain Schu (type A, biovar tularensis) of F. tularensis. Immunisation with a lipopolysaccharide protein complex isolated from the outer membranes afforded protection in CBA mice against challenge with strain 503. Another LPS-protein complex obtained by the simple mixture of LPS preparations from strain 503 and a 17-kDa membrane protein from the avirulent R-variant of the vaccine strain 15 also demonstrated protective properties against experimental tularemia in mice.

[The immunological efficacy of Francisella tularensis outer membranes for hamadryas baboons]. / Immunologicheskaia éffektivnost' vneshnikh membran Francisella tularensis dlia obez'ian-gamadril.

The protective properties of the preparation of F. tularensis outer membranes (OM), obtained from F. tularensis vaccine strain 15, were studied in experiments on hamadryas baboons challenged subcutaneously with F. tularensis virulent strain Schu (nonarctic subspecies). The subcutaneous immunization with the OM preparation prevented the development of clinically pronounced infection in more than 70% of the monkeys challenged with F. tularensis strain Schu in a dose of 787 live microbial cells 30 days after immunization. Antibody titers determined in the immunized monkeys with the use of the agglutination test (AT) and the passive hemagglutination test (PHAT) were usual in minimal diagnostic limits (1:80 for AT and 1:320 for PHAT) and did not significantly rise by day 20 after immunization. In all intact animals infected with F. tularensis strain Schu the development of the infectious process was registered, which was accompanied by a rise in temperature exceeding 39.5 degrees C and a rise in the titer of specific antibodies.

[The protective properties of the outer membranes of Francisella tularensis in an experimental infection in guinea pigs]. / Zashchitnye svoistva vneshnykh membran Francisella tularensis pri éksperimental'noi infektsii morskikh svinok.

Subcutaneous immunization, made in a single injection, with outer membrane preparations obtained from F.tularensis vaccine strain 15 and virulent strain A'Cole results in intensive immunity to tularemia in guinea pigs, ensuring the protection of 60-100% of the animals within a month after challenge with F.tularensis virulent strain 503 in a dose of 1,000 DCL. The development of protective effect induced by F.tularensis outer membranes can be observed during the first 24 hours and reaches its maximum by days 15-21 after immunization.

[The determination of the antigenic determinant of protective monoclonal antibodies specific to the Francisella tularensis lipopolysaccharide]. / Opredelenie antigennoi determinanty preventivnykh monoklonal'nykh antitel, spetsifichnykh k lipopolisakharidu Francisella tularensis.

F. tularensis lipopolysaccharide (LPS) was studied with the use of monoclonal antibodies (McAb) having protective properties. The binding site of these McAb (IgG2a) is localized on the O-chain of LPS. In contrast to LPS isolated from vaccine strain 15, LPS isolated from F. tularensis cells in the R-form has no O-chains and does not interact with McAb.

[The LPS-protein complex from the outer membrane of Francisella tularensis]. / Issledovanie LPS-belkovogo kompleksa iz vneshnei membrany Francisella tularensis.

LPS-protein complex containing proteins of 15 kD, 17 kD and 19 kD was isolated from F. tularensis outer membrane by solving with sodium deoxycholate with the subsequent gel filtration on Sephacryl S-200. Protein of 17 kD constituted the main protein component of the complex. The LPS-protein ratio of this complex was 1:1. Proteins contained in LPS-protein complex have mainly the alpha-spiral structure. In the absence of detergent these proteins and LPS formed micelles with molecular weight exceeding 10(7) D. LPS-protein complex was shown to have a protective effect in mice infected with F. tularensis virulent strain 503.

[The preventive activity of monoclonal antibodies specific to the lipopolysaccharide of Francisella tularensis]. / Preventivnaia aktivnost' monoklonal'nykh antitel, spetsifichnykh k lipopolisakharidu Francisella tularensis.

The preventive activity of five monoclonal antibodies (McAb) in experimental tularemia was evaluated. McAb produced by hybridoma FB11-k (IgG2a), specific to F. tularensis lipopolysaccharide, prevented the death of mice and guinea pigs infected with F. tularensis virulent strain 503 of the holarctic subspecies.

[Biochemical, antigenic and protective properties of the outer membrane of tularemia pathogens]. / Izuchenie biokhimicheskikh, antigennykh i protektivnykh svoistv vneshnei membrany vozbuditelia tuliaremii.

The outer membranes of Francisella tularensis were studied. The membranes were identified morphologically, immunologically and biochemically. They contained 12-20% of protein, 15-30% of carbohydrates, up to 40% of lipids. The main integral proteins of the outer membranes were the 47, 43, 17 and 12 kD proteins. The main protein 63 kD was not integral. The lipopolysaccharides isolated from the outer membranes and acetone-dried cells did not possess the protective properties in experimental tularemia. The preparations of outer membranes possessed the protective properties for mice infected with the virulent strain 503. Chitosan amplified the protective properties of outer membranes.

Structure of the O-antigen of Francisella tularensis strain 15.

The O-specific polysaccharide, obtained by mild acid degradation of the lipopolysaccharide of Francisella tularensis strain 15, contained 2-acetamido-2,6-dideoxy-D-glucose (D-QuiNAc), 4,6-dideoxy-4-formamido-D-glucose (D-Qui4NFm), and 2-acetamido-2-deoxy-D-galacturonamide (D-GalNAcAN) in the ratios 1:1:2. Tri- and tetra-saccharide fragments were obtained on treatment of the polysaccharide with anhydrous hydrogen fluoride and partial hydrolysis with 0.1 M hydrochloric acid, respectively. On the basis of 1H- and 13C-n.m.r. spectroscopy of the polysaccharide and the saccharides, it was concluded that the O-antigen had the structure: ----4)-alpha-D-GalpNAcAN-(1----4)-alpha-D-GalpNAcAN-(1----3) -beta-D-QuipNAc-(1----2)-beta-D-Quip4NFm-(1----. This O-antigen is related in structure to those of Pseudomonas aeruginosa O6, immunotype 1, and IID 1008, and Shigella dysenteriae type 7.