Phage conversion of the antigens in Escherichiae and Shigellae. 2. Conversion of the somatic antigen in Shigella flexneri with the moderate E. coli 0129 phage]

The authors studied the converting activity of the moderate EF5 phage isolated from the lysogenic E. coli 0129 strain. It was shown that this phage converted the O-antigen with the detection of the type antigen V in the strains of Sh. flexneri of the serological type la and y-variant. The converted cultures contained the type antigen V and were identical by the antigenic properties to one another and the Sh. flexneri of the serological type 5 and E. coli 0129. A conclusion was drawn that phages converting the antigens of Sh. flexneri could be encountered in escherichia and could modify the antigens in Sh. flexneri and escherichia possessing the antigenic factor 3,4.     

Antibodies to bacterial and tumor-derived antigens in sera from normal guinea pigs.

Antibodies that react with radiolabeled antigens derived from guinea pig line-10 tumor cells and Mycobacterium bovis (BCG) were detected in sera from normal tumor-free strain-2 guinea pigs (NGPS). Binding by NGPS to the two antigens was inhibited by extracts of either line-10 cells or BCG. Binding by NGPS to the line-10 antigen was inhibited by a number of other bacterial extracts. NGPS was tested after absorption with a variety of cells including line-10, line-1, normal guinea pig spleen, normal adult and fetal liver cells. Results indicated that some of the antibodies in NGPS were directed to line-10-specific determinants. The specific stimulating antigen for these antibodies was not identified but because of the antigenic relationship between BCG, line-10 cells and other bacteria, antibodies to line-10-associated antigens might have been induced by exposure to environmental microorganisms.     

Molecular characterization of the O-acetyl transferase gene of converting bacteriophage SF6 that adds group antigen 6 to Shigella flexneri

Bacteriophage SF6 antigenically converts Shigella flexneri serotype Y strains (-;3,4) to type 3b carrying group antigen 6,3,4 by means of an O-acetylation of the O-antigenic polysaccharide chain. The gene for O-acetyl transferase of bacteriophage SF6 has been cloned, identified and sequenced. The predicted O-acetyl transferase protein encoded by this gene was found to consist of 333 amino acids, (37,185 daltons) and to have some similarity with the galactose-1-phosphate uridylyltransferase protein of Escherichia coli. The gene has been shown to function in a live vaccine strain of S. flexneri Y type (delta aroD), making it a 3b type. The converted type 3b strain, SFL1104, was found to elicit significant protection against challenge by both wild-type serotypes 3b and Y in a guinea-pig keratoconjunctivitis model.     

Determination of Shigella antigens in the feces of people, immunized with enteral vaccine prepared from S. flexneri antigen

The dynamic determination of the presence of the specific antigen and its activity in the excreta of humans subjected to enteral immunization with vaccine prepared from S. flexneri antigen was made in the agglutination test and neutralization test with the use of, respectively, antibody and antigenic erythrocyte diagnosticums. In the feces and urine of the vaccinees antibodies occurred less commonly and, as a rule, they were less active than those detected in dysentery patients at the corresponding time from the beginning of the disease. The occurrence of Shigella antigens in the feces of the vaccinees was greater than in their urine at the corresponding time. Similarities and differences in the dynamics of the isolation of Shigella antigen from dysentery patients and from the vaccinees receiving enteral vaccine prepared from S. flexneri antigens were established.     

Specific blood group antibodies inhibit Shigella flexneri interaction with human cells in the absence of spinoculation

The classical models of investigating Shigella flexneri adherence and invasion of tissue culture cells involve either bacterial centrifugation (spinoculation) or the use of AfaE adhesin to overcome the low infection rate observed in vitro. However clinically, S. flexneri clearly adheres and invades the human colon in the absence of ‘spinoculation’. Additionally, certain S. flexneri tissue cell based assays (e.g. plaque assays and infection of T84 epithelial cells on Transwells®), do not require spinoculation. In the absence of spinoculation, we recently showed that glycan-glycan interactions play an important role in S. flexneri interaction with host cells, and that in particular the S. flexneri 2a lipopolysaccharide O antigen glycan has a high affinity for the blood group A glycan. During the investigation of the effect of blood group A antibodies on S. flexneri interaction with cells, we discovered that Panc-1 cells exhibited a high rate of infection in the absence of spinoculation. Select blood group A antibodies inhibited invasion of Panc-1 cells, and adherence to T84 cells. The use of Panc-1 cells represents a simplified model to study S. flexneri pathogenesis and does not require either spinoculation or exogenous adhesins.     

Monoclonal antibodies against the surface antigens of Shigella flexneri serotype 1b and Shigella dysenteriae serotype 1

Monoclonal antibodies against the surface antigens of Shigella flexneri 1b and S. dysenteriae 1 were prepared. The specificities of the antibodies were evaluated by enzyme-linked immunosorbent assay (ELISA), and quantitative agglutination using microtiter plate. Monoclonal antibodies against S. flexneri 1b, designated Sf2B2 and Sf2G4, belonged to IgG2a and IgG1 subclass, respectively. The former was specific for S. flexneri 1b, whereas the latter was reactive not only to S. flexneri 1b, but also weakly to 3a and 4b. Monoclonal antibody against S. dysenteriae 1, Sd5E1 (IgM), reacted with S. dysenteriae 1, 3, 6, 7, and S. boydii 2.     

Antibodies to saline extractable tissue antigen in sera of patients with renal diseases

Multiple serum samples originating from 110 renal allograft recipients were examined against saline extract of normal human kidney by means of double diffusion gel precipitation. Eleven recipients were found to be positive; 99 of 106 sera from these patients were positive. Pretransplantation sera were available from 7 of these recipients and 6 patients were found "positive." The precipitation reaction was composed of one line. Identity reactions were formed between the lines produced by sera from all patients except 1. Sera of patients from end-stage renal disease produced similar reaction; however, only 3 of 234 sera from patients with nonrenal diseases precipitated the kidney extract. None of 154 normal sera were positive. Several positive sera also were positive in complement fixation tests with human kidney extract. Evidence was presented that the antibodies under study combined with a nonorgan-specific but species-restricted tissue antigen. The hypothesis was advanced that these antibodies are autoantibodies formed in response to a sequestered antigen released as a result of tissue damage. Apparently, the antigen is released frequently in immunogenic form from injury to kidney but infrequently from injury to other organs.     

Cloning and analysis of the glucosyl transferase gene encoding type I antigen in Shigella flexneri

The O-antigen of most Shigella flexneri serotypes contains an identical tetrasaccharide repeating unit. Apart from serotype Y, the O-antigen is modified by addition of a glucosyl and/or O-acetyl residue to a specific position in the O-unit. In this study the glucosyl transferase gene from a serotype 1a has been cloned and identified. The bacteriophage SfV integrase (int) gene was used to probe a S. flexneri Y53 (serotype 1a) cosmid library and 18 unique clones were identified. Southern hybridisation of these clones indicated two unlinked regions of the chromosome contained the int homologue. When expressed in a live candidate vaccine strain of S. flexneri serotype Y (SFL124), clones with one region produced type I antigen, whereas clones containing the other region produced mainly type Y antigen. One of the cosmid clones positive for type I antigen by agglutination and Western blotting was selected for further study. Genes involved in O-antigen glucosyl modification were mapped on a 5.8 kb fragment and subclones were produced which fully or partially expressed the type I antigen, depending on the extent of the clone. Fully and partially expressing clones may be useful vaccine candidate strains for protection against disease caused by two serotypes of S. flexneri.