The Effect of a BSA Conjugate of a Synthetic Hexasaccharide Related to the Fragment of Capsular Polysaccharide of Streptococcus pneumoniae Type 14 on the Activation of Innate and Adaptive Immune Responses.

We report the effect of a bovine serum albumin (BSA) conjugate of a synthetic hexasaccharide (HS) related to the fragment of the capsular polysaccharide (PS) of Streptococcus pneumoniae type 14 on the stimulation of innate immune system and the subsequent development of a PS-specific antibody response. Glycoconjugate (GC) in the presence (GC + AL) or absence of aluminum hydroxide was administered to mice twice. GC increased the number of TLR2-expressing cells and induced the maturation of dendritic cells (CD11c(+), CD80(+) and, MHCII(+)), which secreted IL-1ß, IL-6, and TNFα into the culture medium. The level of IL-1ß, IL-10, IFNγ, and TNFα in the blood increased within 24 h after the single GC administration to mice. On day 7, the numbers of splenic CD4(+) and CD8(+) T lymphocytes and B lymphocytes increased. After the second immunization, the levels of CD4(+) and CD8(+) T lymphocytes were lower than in the control, whereas the B cell, NK cell, and MHC class II-expressing cell numbers remained enhanced. However, of the presence of anti-PS, IgG antibodies were not detected. The addition of aluminum hydroxide to GC stimulated the production of GM-CSF, IL-1ß, IL-5, IL-6, IL-10, IL-17, IFNγ, and TNFα. Anti-PS IgG1 antibody titers 7 days after the second immunization were high. During that period, normal levels of splenic CD4(+) T lymphocytes were maintained, whereas reduced CD8(+) T lymphocyte numbers and increased levels of B lymphocytes, NK cells, and MHC class II-expressing cell numbers were observed. Anti-PS IgG levels diminished until day 92. A booster immunization with GC + AL stimulated the production of anti-PS IgG memory antibodies, which were determined within 97 days. The elucidation of specific features of the effect of the synthetic HS conjugate on the stimulation of innate, cell-mediated immunity, and antibody response can favor the optimization of GC vaccine design.

Activation of innate immunity by bacterial ligands of toll-like receptors.

Tγδ and B1 lymphocytes are essential components of the mucosal immune system, activated directly by different bacterial and viral ligands without additional costimulatory signals and preprocessing of other immune effectors. This ability enables the immune system to provide rapid protection against pathogens and contributes to the decoding mechanism of the sensitizing activity of mucosal antigens. The early interaction of these cells results in the production of antibodies of immunoglobulin M (IgM) and IgA isotypes, but not immunoglobulin E (IgE). We studied the subcutaneous, intranasal, and oral delivery as three major routes of potential entry for antigens of opportunistic microorganisms, using the immunomodulator Immunovac-VP-4, which is able to activate Tγδ and B1 lymphocytes. The subcutaneous and intranasal routes produced a significant increase of these cells in lymph nodes associated with the nasal cavity (NALT) and in those associated with bronchial tissue (BALT). The oral route significantly increased levels of these cells in the spleen, in NALT, BALT, and in nodes associated with the gut (GALT). We found that mucosal application of Immunovac-VP-4, which contains antigens of conditionally pathogenic microorganisms, in conjunction with the activation of Tγδ and B1, induces adaptive immune mechanisms not only in the lymphoid formations associated with the respiratory system and with GALT, but also in the spleen [increased expression of cluster of differentiation 3 (CD3), CD4, CD8, CD19, and CD25]. This indicates that there is migration of lymphoid cells from the regional lymph nodes and mucosal lymphoid tissues via the lymph and blood to distant organs, resulting in lymphoid development, and both local and systemic immunity. Mucosal application of Immunovac-VP-4 in mice potentiates the cytotoxic activity of NK cells in the NALT, BALT, and GALT. The highest cytotoxicity was observed in cells, derived from lymphoid tissue of the intestine after oral immunization. Although we found that cytokine production was increased by all three immunization routes, it was most intensive after subcutaneous injection. Our findings confirm that there is an intensive exchange of lymphocytes not only between lymphoid formations in the mucous membranes of the respiratory tract and of GALT, but also with the spleen, which means that if effective mucosal vaccines are developed, they can induce both local and systemic immunity.