To this day, despite the increasing efficacy of newly developed vaccines, community acquired pneumonia (CAP) remains a major cause of health complications and death. Streptococcus pneumoniae is the most frequent causative pathogen of community acquired pneumonia. It is important to understand the underlying mechanisms of this generally asymptomatic bacteria becoming pathogenic. This research investigates whether community acquired pneumonia patients infected by S. Pneumoniae have a decreased immune response to this bacteria compared to community acquired pneumonia patients whom are infected by another pathogen. A cohort of 60 patients with community acquired pneumonia were divided into two groups: PneuCAP (subjects infected by S. pneumoniae) and OtherCAP (subjects infected by pathogens other than S. pneumoniae). To measure the immunological response to S. Pneumoniae the pneumococcal conjugate vaccine PCV13 was used. Serum samples were obtained before, and 3-4 weeks after vaccination. Serotype specific serum IgG antibody levels were measured with Luminex technology. The vaccine proved to be immunogenic in both groups. Furthermore, for serotype 1 and 9V, mean IgG concentrations were significantly higher in OtherCAP compared to PneuCAP after vaccination. Besides the significant differences found between groups, it was found that subjects in the OtherCAP group generally have higher fold increase values compared to PneuCAP subjects. Overall, it can be suggested that community acquired pneumonia patients infected by S. Pneumonia have a decreased antibody response to the bacterial polysaccharides compared to patients infected by another pathogen.
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