Pneumococcal 6-phosphogluconate-dehydrogenase, a putative adhesin, induces protective immune response in mice

For most bacteria, adherence to human cells is achieved by bacterial lectins binding to mammalian surface glyconjugates. 6-Phosphogluconate dehydrogenase (6PGD) was identified by us as one of Streptococcus pneumoniae cell wall lectin proteins, which elicits an age-dependent immune response in humans. This study assesses the role of 6PGD in S. pneumoniae pathogenesis as an adhesin and its ability to elicit a protective immune response in mice. Recombinant 6PGD (r6PGD) was cloned from S. pneumoniae serotype 3 (strain WU2). r6PGD interference in adhesion of three genetically unrelated unencapsulated pneumococcal strains (3.8, 14.8 and R6) and two genetically unrelated encapsulated pneumococcal strains (WU2 and D39) to A549 type II lung carcinoma cell was tested. BALB/c mice were immunized with r6PGD and boosted after 3 weeks. Immunized mice were challenged intranasally with a lethal dose of S. pneumoniae. r6PGD inhibited 90% and 80% of pneumococcal adhesion to the A549 cells of three unencapsulated S. pneumoniae strains and two encapsulated S. pneumoniae strains, respectively, in a concentration-dependent manner (P < 0.05). Antibodies to r6PGD produced in mice significantly inhibited bacterial adhesion to A549 cell (P < 0.05). Immunization of mice with r6PGD protected 60% (P < 0.001) of mice for 5 days and 40% (P < 0.05) of the mice for 21 days following intranasal lethal challenge. We have identified 6PGD as a surface-located immunogenic lectin protein capable of acting as an adhesin. 6PGD importance to bacterial pathogenesis was demonstrated by the ability of r6PGD to elicit a protective immune response in mice.

Glycolytic enzymes associated with the cell surface of Streptococcus pneumoniae are antigenic in humans and elicit protective immune responses in the mouse

Streptococcus pneumoniae is a leading cause of otitis media, sinusitis, pneumonia, bacteraemia and meningitis worldwide. The drawbacks associated with the limited number of various capsular polysaccharides that can be included in the polysaccharide-based vaccines focuses much attention on pneumococcal proteins as vaccine candidates. We extracted an enriched cell wall fraction from S. pneumoniae WU2. Approximately 150 soluble proteins could be identified by 2D gel electrophoresis. The proteins were screened by 2D-Western blotting using sera that were obtained longitudinally from children attending day-care centres at 18, 30 and 42 months of age and sera from healthy adult volunteers. The proteins were further identified using matrix-assisted laser desorption ionization-time of flight mass spectrometry. Seventeen proteins were antigenic in children and adults, of which 13 showed an increasing antibody response with age in all eight children analysed. Two immunogenic proteins, fructose-bisphosphate aldolase (FBA) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and a control protein with known low immunogenicity, heat shock protein 70 (DnaK), were expressed in Escherichia coli, purified and used to immunize mice. Mouse antibodies elicited to the recombinant (r) FBA and rGAPDH were cross-reactive with several genetically unrelated strains of different serotypes and conferred protection to respiratory challenge with virulent pneumococci. In addition, the FBA used in this study (NP_345117) does not have a human ortholog and warrants further investigation as a candidate for a pneumococcal vaccine. In conclusion, the immunoproteomics based approach utilized in the present study appears to be a suitable tool for identification of novel S. pneumoniae vaccine candidates.

Usefulness of fluorescence in situ hybridization for the diagnosis of Turner mosaic fetuses with small ring X chromosomes

OBJECTIVE

To emphasize the usefulness of fluorescence in situ hybridization (FISH) techniques on uncultured amniocytes for the diagnosis of abnormal mosaic karyotypes.

METHODS

In the course of three prenatal diagnoses, specific fluorescent probes, coding, respectively, for chromosomes X, Y, 18, 13, and 21, were applied on amniocyte preparations directly after amniocentesis. At least 50 nuclei were counted in each case. Parallel to the FISH procedure, cell cultures were set up in order to obtain karyotypes. FISH and cytogenetic results were then compared.

RESULTS

In each case, FISH showed an abnormal mosaic chromosomal constitution, 45,X/46,XX, which was related to the existence of tiny ring X chromosomes in karyotypes.

CONCLUSION

Because very small ring X chromosomes can escape identification when standard cytogenetic techniques are used alone, we show that misdiagnosis can be avoided when FISH is performed beforehand.