Initial steps in Streptococcus pneumoniae interaction with and pathogenicity to the host

Glycan binding profile of a fucolectin-related protein (FRP) encoded by the SP2159 gene of Streptococcus pneumoniae

The recombinant fucolectin-related protein (FRP) of unknown function, encoded by the SP2159 gene of Streptococcus pneumoniae, was expressed in E. coli. In this study, its glycan-recognition epitopes and their binding potencies were examined by enzyme-linked lectinosorbent and inhibition assays. The results indicate that FRP reacted strongly with human blood group ABH and l-Fucα1→2-active glycotopes and in their polyvalent (super) forms. When expressed by mass relative potency, the binding affinities of FRP to poly-l-Fucα1→glycotopes were about 5.0 × 10⁵ folds higher than that of the mono-l-Fucα1→glycotope form. This unique binding property of FRP can be used as a special tool to differentiate complex forms of l-Fucα1→2 and other forms of glycotopes.

Aggregates of ultrafine particles modulate lipid peroxidation and bacterial killing by alveolar macrophages

We hypothesized that aggregates of ultrafine carbon and washed diesel particles impair the ability of alveolar macrophages (AM) to kill bacteria and enhance the AM lipid peroxidation (LPO) of lung surfactant. Rat AM were exposed, 5h, to particles 20 microg/ml. The AM, containing carbon or washed diesel particles, were incubated 2h, with Streptococcus pneumoniae, an American Type Culture Collection (ATCC) strain or clinical isolates. Surviving bacteria were quantified. Surfactant was incubated, 5h, with carbon or washed diesel loaded AM and LPO was measured. The particle load was approximately 1 microg/10(6) AM, representing accepted exposure to ambient particles in Europe. Metal concentrations were 10 to 100 fold higher in washed diesel--than in carbon particles. There was a dose dependent increase in bacterial survival with carbon-loaded macrophages, but not with washed diesel-loaded AM. Clinical isolates had a higher survival rate with carbon-loaded macrophages than the ATCC strain. Surfactant LPO was increased with washed diesel-loaded macrophages (95%) and with carbon-loaded macrophages (55%) compared to controls. High LPO caused by washed diesel-loaded AM reflects their increased oxidative metabolism, probably caused by particle metals. The additional oxygen metabolites maintained bactericidal activity of AM, while corresponding activity was decreased in carbon-loaded AM. Altered functions of AM may explain health problems related to air pollution.

Differential activation of inflammatory pathways in A549 type II pneumocytes by Streptococcus pneumoniae strains with different adherence properties

Background

Adherence of Streptococcus pneumoniae bacteria to lung cells is a first step in the progression from asymptomatic carriage to pneumonia. Adherence abilities vary widely among S. pneumoniae patient isolates. In this study, the binding properties of S. pneumoniae isolates and the effects of binding on activation of the Nuclear Factor-Kappa-B (NFκB) pathway and cytokine secretion by type II pneumocytes were measured.

Methods

Mechanisms of high- and low-binding S. pneumoniae adherence to A549 cells were investigated by blocking putative receptors on bacteria and host cells with antibody and by eluting choline-binding proteins off of bacterial surfaces. NFκB activation was measured by western blot and immunocytochemistry and cytokine secretion was detected by a protein array.

Results

This study shows that S. pneumoniae isolates from pneumonia patients (n = 298) can vary by as much as 1000-fold in their ability to bind to human lung epithelial cells. This difference resulted in differential activation of the NFκB pathway. High-, but not low-binding S. pneumoniae used Choline-binding protein A (CbpA) to bind to complement component C3 on epithelial cell surfaces. Interleukin-8 (IL-8) was the only cytokine secreted by cells treated with either low- or high-binding S. pneumoniae.

Conclusion

These results indicate that S. pneumoniae clinical isolates are not homogeneous in their interaction with host epithelial cells. The differential activation of host cells by high- and low-binding S. pneumoniae strains could have implications for the treatment of pneumococcal pneumonia and for vaccine development.

The vaccine potential of Streptococcus pneumoniae surface lectin- and non-lectin proteins

We have fractionated S. pneumoniae surface proteins into lectin and non-lectin fractions and tested their ability to elicit protective immune responses in the mouse model system. The total cell wall protein fraction (CW-T) was separated into lectin (CW-L), and non-lectin (CW-NL) fractions and used for immunization of mice. Immunized mice were challenged intranasally or intraperitoneally with S. pneumoniae strain WU2 (serotype 3). CW-T, CW-NL and CW-L and adjuvant only vaccination protected 55%, 43%, 44% and 0% of the intranasally challenged mice, respectively and 67%, 86%, 11% and 0% of mice challenged intraperitoneally, respectively. Immunogenic proteins in each fraction were sequenced and identified using MALDI-TOF. CW-L proteins provided a significantly better protection against intranasal inoculation and CW-NL proteins provided a significantly better protection from intraperitoneal inoculation. Proteins identified by sera from mice immunized with the cell-wall derived fractions may constitute candidates for future development of anti S. pneumoniae vaccines.

Pneumococcal pneumonia in the UK--how herd immunity affects the cost-effectiveness of 7-valent pneumococcal conjugate vaccine (PCV)

This study examines the potential clinical and economic benefits for adults arising from paediatric pneumococcal vaccination in the UK. A UK birth cohort model with a 10-year horizon and using a primary 4-dose paediatric 7-valent pneumococcal conjugate vaccine (PCV) schedule was populated with 1999 morbidity and mortality data scaled up to the UK population. Herd immunity effects on adult pneumococcal hospital-treated pneumonia, meningitis and septicaemia, but not on community-treated pneumonia, were calculated using the lower end of the confidence intervals published for the effects in the US. Universal paediatric pneumococcal immunisation would prevent 1168 deaths (1141 adults) and 7147 cases (1791 adults constituted by 32 meningitis, 37 septicaemia and 1722 pneumonia) of serious pneumococcal infection (meningitis, septicaemia, pneumonia) with a resultant direct (payor) cost per life year gained of 4360 pounds. The 7-valent PCV appears to be highly cost effective.