Vaccines for the prevention of encapsulated bacterial diseases: current status, problems and prospects for the future

Adhesion of Streptococcus pneumoniae to human pharyngeal epithelial cells in vitro: differences in adhesive capacity among strains isolated from subjects with otitis media, septicemia, or meningitis or from healthy carriers

A method was developed to study the adhesion of Streptococcus pneumoniae to human pharyngeal epithelial cells. Epithelial cells from healthy persons, pneumococcal strains from patients with otitis media, meningitis, or septicemia, and pneumococcal cells from the nasopharynx of healthy carriers were used. Adhesion was found to be influenced by changes in the bacterial incubation medium and growth phase, the concentration of bacteria and epithelial cells, the epithelial cell donor, the incubation time and temperature, and the pH and osmolarity of the incubation medium. Pretreatment of bacteria with heat, Formalin, or trypsin decreased adhesion. The highest adhesion was obtained when 10(9) bacteria cultivated for 18 h in streptococcus cultivation broth were added to 10(4) pharyngeal cells and incubated at 37 degrees C for 30 min. S. pneumoniae strains from patients with frequent episodes of otitis media and strains from healthy carriers had the highest adhesion values; septicemia and meningitis strains had the lowest. The capsular polysaccharide type did not determine the adhesive capacity of the strains, but otitis strains belonging to the capsular types often associated with otitis media adhered in high numbers. Adhesion may be important for pneumococci colonizing the nasopharynx or inducing otitis media.

Structural studies of the Haemophilus influenzae type e capsular polysaccharide

The structure of the Haemophilus influenzae type e capsular polysaccharide has been determined by a combination of chemical and spectroscopic methods. The structure of the repeating unit of the polymer was found to be leads to 3)-beta-D-GlcNAc-(1 leads to 4)-beta-D-ManANAc-(1 leads to ; both sugars were present in the pyranoid form.

Preparation, characterization, and immunogenicity of Haemophilus influenzae type b polysaccharide-protein conjugates

A method is presented for covalently bonding Haemophilus influenzae type b capsular polysaccharide (HIB Ps) to several proteins. The method is efficient and relies upon the use of adipic dihydrazide as a spacer between the capsular polysaccharide and the carrier protein. In contrast to the poor immunogenicity of the purified HIB Ps in mice and rabbits, the HIB Ps-protein conjugates induced serum anti-type b antibodies having bactericidal activity at levels shown to be protective in humans when low doses were injected subcutaneously in a saline solution. The antibody response in mice was related to the dose of the conjugates, increased with the number of injections, and could be primed by the previous injection of the carrier protein. The HIB Ps-protein conjugates were immunogenic in three different mouse strains. The importance of the carrier molecule for the enhanced immunogenicity of the HIB Ps-protein conjugates was shown by the failure of HIB Ps hybrids prepared with either the homologous polysaccharide or pneumococcus type 3 polysaccharide to induce antibodie in mice. Rabbits injected with the HIB Ps-protein conjugates emulsified in Freund's adjuvant produced high levels of serum anti-type b antibodies which induced a bactericidal effect upon H. influenzae type b organisms. It is proposed that the HIB Ps component of the polysaccharide protein conjugates has been converted to a thymic-dependent immunogen. This method may be used to prepare protein-polysaccharide conjugates with HIB Ps and other polysaccharides to be considered for human use.

Comparison of counterimmunoelectrophoresis and the capsular reaction test for typing of pneumococci

The capsular reaction test is recommended as the method of choice for typing of pneumococci. Counterimmunoelectrophoresis also works in most cases, but has the following definite drawbacks. (i) The polysaccharide type antigens of types 7F, 7A, 14, 33F, 33A, and 37 are neutral and therefore do not form precipitates when conventional buffers are used. (ii) Counterimmunoelectrophoresis does not permit differentiation between types within groups since many factor sera do not contain sufficient amounts of precipitating antibodies. Omniserum contains low-titered antibodies against cell wall antigens and also reacts with thioglycolate-containing broth.