Differential Effect of TLR2 and TLR4 on the Immune Response after Immunization with a Vaccine against Neisseria meningitidis or Bordetella pertussis

Neisseria meningitidis and Bordetella pertussis are Gram-negative bacterial pathogens that can cause serious diseases in humans. N. meningitidis outer membrane vesicle (OMV) vaccines and whole cell pertussis vaccines have been successfully used in humans to control infections with these pathogens. The mechanisms behind their effectiveness are poorly defined. Here we investigated the role of Toll-like receptor (TLR) 2 and TLR4 in the induction of immune responses in mice after immunization with these vaccines. Innate and adaptive immune responses were compared between wild type mice and mice deficient in TLR2, TLR4, or TRIF. TRIF-deficient and TLR4-deficient mice showed impaired immunity after immunization. In contrast, immune responses were not lower in TLR2−/− mice but tended even to be higher after immunization. Together our data demonstrate that TLR4 activation contributes to the immunogenicity of the N. meningitidis OMV vaccine and the whole cell pertussis vaccine, but that TLR2 activation is not required

Differential B-cell memory around the 11-month booster in children vaccinated with a 10- or 13-valent pneumococcal conjugate vaccine

BACKGROUND: Both the 10- and 13-valent pneumococcal conjugate vaccines (PCV10 and PCV13) induce immunological memory against Streptococcus pneumoniae infections caused by vaccine serotypes. In addition to comparing serum antibody levels, we investigated frequencies of serotype-specific plasma cells (PCs) and memory B-cells (Bmems) as potential predictors of long-term immunity around the booster vaccination at 11 months of age. METHODS: Infants were immunized with PCV10 or PCV13 at 2, 3, 4, and 11 months of age. Blood was collected before the 11-month booster or 7-9 days afterward. Serotype-specific immunoglobulin G (IgG) levels were determined in serum samples by multiplex immunoassay. Circulating specific PCs and Bmems against shared serotypes 1, 6B, 7F, and 19F and against PCV13 serotypes 6A and 19A were measured in peripheral blood mononuclear cells by enzyme-linked immunospot assay. RESULTS: No major differences in IgG levels and PC frequencies between groups were found for the 4 shared serotypes. Notably, PCV13 vaccination resulted in higher frequencies of Bmems than PCV10 vaccination, both before and after the booster dose, for all 4 shared serotypes except for serotype 1 postbooster. For PCV13-specific serotypes 6A and 19A, the IgG levels and frequencies of PCs and Bmems were higher in the PCV13 group, pre- and postbooster, except for PC frequencies prebooster. CONCLUSIONS: Both PCVs are immunogenic and induce measurable IgG, PC, and Bmem booster responses at 11 months. Compared to PCV10, vaccination with PCV13 was associated with overall similar IgG levels and PC frequencies but with higher Bmem frequencies before and after the 11-month booster. The clinical implications of these results need further follow-up. CLINICAL TRIALS REGISTRATION: NTR3069

Antibody titers of mice after immunization with <i>N. meningitidis</i> P1.5-1,2-2 OMVs.

<p>Mice were immunized with <i>N. meningitidis</i> P1.5-1,2-2 OMVs and antigen-specific titers of IgG, IgG1, IgG2a/c, IgG2b, and IgG3 in sera were determined with ELISA. Also total IgE in sera of mice immunized with PBS or <i>N. meningitidis</i> P1.5-1,2-2 OMVs was measured with ELISA. Results for C57BL/6, TLR2−/−, and TRIF-deficient (TRIFdef) mice are shown in panel A, results for C3H/HeOuJ and C3H/HeJ mice are shown in panel B. Levels of serum bactericidal antibodies after immunization with <i>N. meningitidis</i> P1.5-1,2-2 OMVs are shown in panel C. Data are expressed as means of log₁₀ titers for 6 mice per group, except levels of serum bactericidal antibodies in C57BL/6 and TLR2−/− mice (n = 12). Error bars represent S.E.M. An asterisk indicates a significant difference compared to the wild type group, * indicates p<0.05, ** indicates p<0.01.</p

Cytokines produced by spleen cells after restimulation with FHA.

<p>Spleen cells from C57BL/6, TLR2−/−, TRIF-deficient (TRIFdef) mice (A), or C3H/HeOuJ and C3H/HeJ mice (B) immunized with PBS or whole cell pertussis vaccine were incubated for 4 days with 500 ng/ml FHA Cytokines IL-2, IL-4, IL-5, IL-10, IL-13, IL-17, and IFN-γ were determined in the supernatant with Luminex. Data are expressed as means of three mice per group (PBS), or six mice per group (whole cell pertussis vaccine), error bars represent S.E.M. An asterisk indicates a significant difference compared to the wild type group, * indicates p<0.05, ** indicates p<0.01.</p

Antibody titers of mice after immunization with whole cell pertussis vaccine.

<p>Mice were immunized with whole cell pertussis vaccine (<i>Bordetella pertussis</i>) and antigen-specific titers of IgG, IgG1, IgG2a/c, IgG2b, and IgG3 in sera were determined with ELISA. Also total IgE in sera of mice immunized with PBS or whole cell pertussis vaccine was measured with ELISA. Results for C57BL/6, TLR2−/−, and TRIF-deficient (TRIFdef) mice are shown in panel A, results for C3H/HeOuJ and C3H/HeJ mice are shown in panel B. Data are expressed as means of log₁₀ titers for 6 mice per group. An asterisk indicates a significant difference compared to the wild type group, * indicates p<0.05, ** indicates p<0.01.</p

Proliferation of spleen cells after restimulation with antigen or peptide.

<p>Spleens were taken from the mice after immunizations and spleen cells were incubated for 4 days with medium, antigen, or peptides, after which [³H]thymidine incorporation was determined. Spleen cells of C57BL/6, TLR2−/−, and TRIF-deficient (TRIFdef) mice immunized with PBS (3 mice per group) or <i>N. meningitidis</i> P1.5-1,2-2 OMVs (6 mice per group) were restimulated with 1 µM of peptides 11–24/25 and 4–52/53 (A). Spleen cells of C3H/HeOuJ and C3H/HeJ mice immunized with PBS (3 mice per group) or <i>N. meningitidis</i> P1.5-1,2-2 OMVs (6 mice per group) were restimulated with peptide pool 6 (1 µM of each peptide, B). Spleen cells of C57BL/6, TLR2−/−, TRIF-deficient, C3H/HeOuJ, and C3H/HeJ mice immunized with PBS (3 mice per group) or whole cell pertussis vaccine (<i>B. pertussis</i>, 6 mice per group) were restimulated with 500 ng/ml of FHA antigen (C). Data are expressed as means of stimulation indices.</p

Cytokines produced by spleen cells after restimulation with P1.5-1,2-2 PorA peptides.

<p>Spleen cells from C57BL/6, TLR2−/−, or TRIF-deficient (TRIFdef) mice immunized with PBS or <i>N. meningitidis</i> P1.5-1,2-2 OMVs were incubated for 4 days with peptide 11–24/25 (A) or peptide 4–52/53 (B). Spleen cells from C3H/HeOuJ and C3H/HeJ mice immunized with PBS or <i>N. meningitidis</i> P1.5-1,2-2 OMVs were incubated for 4 days with peptide pool 6 (C). Cytokines IL-4, IL-5, IL-10, IL-13, IL-17, and IFN-γ were determined in the supernatant with Luminex. Data are expressed as means of three mice per group (PBS), or six mice per group (<i>N. meningitidis</i> OMVs), error bars represent S.E.M. An asterisk indicates a significant difference compared to the wild type group, * indicates p<0.05, ** indicates p<0.01.</p