The log antibody concentrations one month post-mPPS are significantly associated with the pre-mPPS antibody concentration for all 16 non-PCV serotypes (each p < 0.001). Having selleck products adjusted for the pre-mPPS log antibody concentration, exposure to 23vPPS was associated with a lower response to mPPS for all 16 non-PCV serotypes (each p < 0.001). For PCV serotypes, a similar response was demonstrated.

The response one month post-mPPS was significantly associated with the pre-mPPS antibody concentration for all seven PCV serotypes (p < 0.001) and having adjusted for the pre-mPPS concentration, prior exposure to 23vPPS was associated with a lower response to mPPS (each p < 0.001). In contrast, most children who had not received 23vPPS had an increase in antibody concentration. A joint test rejected the

null hypothesis of mPPS having no impact on the antibody response to any of the 23 serotypes, having adjusted for the pre-mPPS antibody concentrations (p < 0.001). There were 101 SAE's throughout the study period with none attributable to receipt of any of the study vaccines. In children over 12 months of age, there were 14 SAE's in the 12 month 23vPPS group and 22 SAE's in the group that did not receive the 23vPPS. There were four cases of inpatient pneumonia in children who had received the 12 month 23vPPS compared to seven cases in those that had not, www.selleckchem.com/products/PF-2341066.html in infants aged over 12 months of age. There were no cases of IPD throughout the study period. This is the first study in children, using the third generation WHO ELISA assay to measure antibody responses

to all 23vPPS serotypes following receipt of that vaccine. The results show that prior receipt of 23vPPS causes immune hyporesponsiveness to a subsequent 23vPPS challenge. Despite those children who received the 12 month 23vPPS having higher circulating antibody concentrations at 17 months of age, their responses to a re-challenge with a small dose of 23vPPS demonstrated a profound lack of response to all 23 serotypes after adjusting for the pre-existing antibody concentration. In contrast, those children who had not received the 12 month 23vPPS 3-mercaptopyruvate sulfurtransferase could clearly mount a satisfactory response to mPPS. There are a number of potential immunological mechanisms that may explain these findings. In vitro studies have suggested that polysaccharides antigens may be able to down regulate B cells [30], and that newly formed antibody via IgG, IgM, or immune complexes can bind to inhibitory Fc receptors and prevent antibody production [31]. The critical role of pneumococcal-specific memory B cells in first line of defense against pneumococcal infection has recently become an important area of research.