Meningococcal serogroup C polysaccharide specific memory B cells, directly enumerated by labeled polysaccharide, are not affected by age at vaccination.

The influence of age on the generation and persistence of specific memory B cells after vaccination with Neisseria meningitidis type C polysaccharide (MenC-PS) conjugate is unknown. MenC-PS-specific B cells could be directly enumerated by fluorochrome-labeled MenC-PS and flow cytometry in blood up to at least 4 years after vaccination, ranging from 0.01% to 0.

Effects of LT-K63 and CpG2006 on phenotype and function of murine neonatal lymphoid cells.

The immature state of the immune system of neonates makes them vulnerable to infectious agents, including Streptococcus pneumoniae. The aim of our study was to analyse and compare the effects of Escherichia coli heat-labile enterototoxin (LT)-K63 and CpG2006 on cells and key molecules of the neonatal immune system, using a previously established immunization model with pneumococcal polysaccharide of serotype 1 conjugated to tetanus toxoid (TT) (Pnc1-TT). The cellular response was evaluated by measuring cytokine secretion and proliferation upon in vitro stimulation with TT, the protein moiety of Pnc1-TT, and antibody (Ab) to both the polysaccharide (PS) and protein parts of the vaccine were measured by enzyme-linked immunosorbent assay (ELISA).

Early life T cell responses to pneumococcal conjugates increase with age and determine the polysaccharide-specific antibody response and protective efficacy.

Immunization with a tetanus-protein (TT) pneumococcal polysaccharide (PPS) conjugate vaccine (Pnc1-TT) induces protective immunity against lethal pneumococcal infections in neonatal and infant mice, but anti-PPS IgG response and protective efficacy is lower than in adult mice. Here, we show that reduced antibody (Ab) response and protection against infections is directly related to impaired T cell response to the carrier. Whereas spleen cells from adult mice immunized with Pnc1-TT responded with proliferation and IFN-gamma secretion to in vitro stimulation with TT, spleen cells from neonatal and infant mice did not.