Jørgen Henrichsen

Covalent linkage between the capsular polysaccharide and the cell wall peptidoglycan of Streptococcus pneumoniae revealed by immunochemical methods

The attachment of capsular polysaccharide to Streptococcus pneumoniae was examined using monoclonal and polyclonal antibodies. Among the strains examined, the capsular polysaccharide of types 2, 4, 6A, 6B, 7F, 8, 14, 19F and 23F was bound to the pneumococci whereas that of a type 3 strain was not. Sequential treatment with 2% SDS at 100 degrees C, pronase, and EDTA did not dissociate the capsular polysaccharide from the pneumococci. Treatment of the cells with mutanolysin, a muramidase that degrades the cell wall peptidoglycan of pneumococci and other streptococci, released both the capsular and the cell wall C-polysaccharide (C-Ps). Type 6A capsular polysaccharide released from cell walls by mutanolysin treatment, was fractionated by high performance liquid chromatography and examined by immunoelectrophoresis. It was found to be bound to both the C-Ps and the peptidoglycan. The bond between the capsular polysaccharide and the peptidoglycan has not yet been identified but is probably covalent, as the two components could not be dissociated after boiling in SDS. Based on our studies with type 6A, we propose that capsular polysaccharide and C-Ps of the pneumococcus are linked to the peptidoglycan at different sites and, thereby, indirectly to each other. Studies in mice showed that the peptidoglycan enhanced the serum antibody response to C-Ps but not to type 6A polysaccharide.

Immunogenicity and safety of a 23-valent pneumococcal polysaccharide vaccine in healthy children and in children at increased risk of pneumococcal infection.

Splenectomized children as well as those suffering from nephrotic syndrome or recurrent asthmatic bronchitis have an increased susceptibility to systemic pneumococcal infections compared to healthy children. To determine the immunogenicity and safety of a 23-valent pneumococcal polysaccharide vaccine (PPV), 119 children (21 healthy, 26 splenectomized children, 48 with nephrotic syndrome and 24 with recurrent asthmatic bronchitis), aged 2-18 years, received one subcutaneous injection of a 23-valent PPV. Anti-capsular antibodies (Ab) to types 6B, 9V, 14, 18C, 19F and 23F were measured by ELISA before and 4 weeks after immunization. In all cases the adverse reactions were mild and transient, consisting of local pain and/or erythema or swelling in 41% and fever above 38.5 degrees C in 2% of the children. The healthy children responded well to vaccination with a mean fold increase (FI) of 2.6 in postvaccination Ab titers compared to prevaccination titers. The combined geometric mean Ab concentrations in the high-risk children were significantly lower than those of healthy children both before and after vaccination. However, the combined geometric mean FI were not significantly different between high-risk and healthy children. These results indicate that PPV is immunogenic and safe in high-risk as well as in healthy Korean children.

A modified enzyme-linked immunosorbent assay for measuring type-specific anti-pneumococcal capsular polysaccharide antibodies.

We have developed an ELISA for antibody determination, superior to others hitherto described, in which optimal coating is achieved using phenylated pneumococcal capsular polysaccharides as coating antigen. The specificity of the assay is ensured by complete inhibition of antibodies against the species-specific pneumococcal antigen, C-polysaccharide (C-Ps). The method is sensitive, specific, reproducible, fast and easy to work with and can be used for both immunoglobulin class and subclass antibody determinations.

Rapid Emergence of Penicillin-resistant Pneumococci in Hong Kong

The prevalence of penicillin resistance in Streptococcus pneumoniae isolated at the Prince of Wales Hospital, Hong Kong, rose from 6.6% of sputum isolates in the first quarter of 1993 to 55.8% of isolates in the second quarter of 1995. Most of the isolates were also resistant to co-trimoxazole, tetracycline, choramphenicol and erythromycin. Type 19F was the most common capsular type in 1993-1994, comprising 40.0% of typed isolates in this period. Type 23F emerged in 1995 as the predominant type, making up 62.2% of typed isolates in the first 2 quarters of 1995. A high population density and excessive community use of antibiotics are likely to be factors promoting the rapid emergence of multiply-resistant pneumococci in Hong Kong.

Capsular types and susceptibility to penicillin of pneumococci isolated from cerebrospinal fluid or blood in Denmark, 1983-1988

By means of the capsular reaction test, we typed 2,294 pneumococcal strains isolated from blood or cerebrospinal fluid (CSF) in Denmark during 1983-88.91% of the strains belonged to types included in the 23-valent vaccine. Among 254 pneumococcal isolates from blood and CSF from Danish children, types 6A + 6B, 18C, 14, 7F, 1 and 19F, in that order of frequency, were the most common ones, accounting for 68%. Among 2,031 pneumococcal strains from adults, the most common isolates were types 1, 3, 14, 7F, 4, and 6A + 6B, accounting for 50% of all pneumococcal strains isolated from patients with invasive disease. Penicillin-resistant invasive strains of Streptococcus pneumoniae are rare in Denmark (< 1%).

Antibody response to pneumococcal vaccine in patients with early stage Hodgkin's disease

Antibody response to pneumococcal vaccination was studied in 76 patients with Hodgkins disease (HD) before, during and at different time intervals after cessation of therapy. All patients were in pathological stage I and II following explorative laparatomy with splenectomy. The increase in antibody response was compared to the findings in 12 healthy volunteers with the aim of establishing the optimal time for vaccination. Serum antibodies against 6 of the pneumococcal polysaccharide antigens (types 1, 4, 7F, 14, 18C and 23F) contained in the vaccine were determined by an ELISA. Antibody response to pneumococcal type antigens was similar in healthy adults and in patients with early stage HD before therapy. After treatment, post‐vaccination antibody response became negligible. Even up to 7 years after cessation of therapy patients were not able to raise a significant antibody response.

Serotype Distribution of Streptococcus pneumoniae Strains Isolated from Blood and Cerebrospinal Fluid in Sweden

215 strains of Streptococcus pneumoniae isolated from blood or cerebrospinal fluid at 3 different laboratories in Sweden were serotyped by coagglutination and subtyped by the capsular reaction test. 78% of the strains belonged to serotypes which are included in or completely cross-immunogenic with serotypes included in the 14-valent vaccine while serotypes included in the 23-valent vaccine covered 89% of the isolates. Types 7F, 14 and 33F, which cannot be detected by counterimmunoelectrophoresis constituted 19% of all strains.

Antibody Persistence in Splenectomized Adults after Pneumococcal Vaccination

16 splenectomized adults, all vaccinated with a 14-valent pneumococcal vaccine (Pneumovax) 1978-79 had their pneumococcal antibody concentrations measured before and up to 10 years after vaccination. The antibody concentrations after vaccination declined to 71% in 2 years and remained at this level during the 10-year study period. Further studies are needed to see whether this applies to all vaccinated splenectomized adults.

Detection of pneumococcal polysaccharide antigens in the urine of patients with bacteraemic and non-bacteraemic pneumococcal pneumonia

Countercurrent-immunoelectrophoresis (CIE) was used to detect pneumococcal capsular polysaccharide and C-polysaccharide (C-Ps) antigens in urine. The neutral capsular polysaccharides of types 7F and 14 were detected by coagglutination. We found pneumococcal polysaccharide in urine with the same frequency in two groups of patients, i.e. a non-bacteraemic pneumonia group (68%) and a group of patients with pneumococcal bacteraemia (66%). C-Ps was detected in the urine of two patients (4%) and, therefore, this test has no value in the diagnosis of pneumococcal infections. Since there is no sensitive, non-invasive, single procedure for the diagnosis of non-bacteraemic pneumococcal pneumonia we conclude that attempts to detect pneumococcal capsular polysaccharide by CIE in combination with coagglutination (types 7F and 14) may be a useful diagnostic supplement in the search for the etiological agent in pneumonia in adults until new, more sensitive diagnostic methods have been developed.

Antibody Response to Pneumococcal Vaccination in the Elderly

In order to evaluate the antibody response to primary pneumococcal vaccination in the elderly, 20 healthy persons aged 60 years or older, (mean age 62.8) were vaccinated with a 23-valent pneumococcal polysaccharide vaccine (Pneumovax 23). Blood samples were taken before and 4 weeks after vaccination and pneumococcal antibody concentrations were measured by ELISA and compared with those obtained after vaccination of younger persons (mean age 39 years). Significantly lower anti-type 2 antibody concentrations were found in the elderly after vaccination. Apart from this, no other significant differences were found neither in pre- and post-vaccination antibody concentrations nor in antibody fold increases between the two groups.