Immunogenicity of meningococcal polysaccharide ACWY vaccine in primary immunized or revaccinated adults.

Meningococcal polysaccharide (Men-Ps) vaccine immunogenicity following either primary immunization or revaccination in adults was evaluated. The study population consisted of subjects who have received tetravalent Men-Ps vaccine once (group 1) or at least twice, with a 2-6 dose range (group 2). Human leucocyte antigen (HLA)-typing was performed by polymerase chain reaction and specific immunoglobulin (Ig)G was measured by enzyme-linked immunosorbent assay. Nine months post-immunization, the percentages of individuals with levels of anti-Men-Ps IgG ≥ 2 µg/ml were comparable in both groups, with the exception of anti-Men-PsW135 IgG, which were significantly higher in group 2. The percentage of subjects doubling IgG levels at 9 months was significantly higher in group 1. The high baseline anti-Men-Ps antibody levels negatively influenced the response to revaccination, suggesting a feedback control of specific IgG. The calculated durability of anti-Men-Ps IgG was 2·5-4·5 years, depending on the Men-Ps, following a single vaccine dose. No interference by other vaccinations nor HLA alleles association with immune response were observed. This study confirms that Men-Ps vaccine in adults is immunogenic, even when administered repeatedly, and underlines the vaccine suitability for large-scale adult immunization programmes that the higher costs of conjugate vaccines may limit in developing countries.

Antibody classes & subclasses induced by mucosal immunization of mice with Streptococcus pyogenes M6 protein & oligodeoxynucleotides containing CpG motifs.

BACKGROUND & OBJECTIVES: Type-specific antibodies against M protein are critical for human protection as they enhance phagocytosis and are protective. An ideal vaccine for the protection against Streptococcus pyogenes would warrant mucosal immunity, but mucosally administered M-protein has been shown to be poorly immunogenic in animals. We used a recombinant M type 6 protein to immunize mice in the presence of synthetic oligodeoxynucleotides containing CpG motifs (immunostimulatory sequences: ISS) or cholera toxin (CT) to explore its possible usage in a mucosal vaccine. METHODS: Mice were immunized by intranasal (in) or intradermal (id) administration with four doses at weekly intervals of M6-protein (10 microg/mouse) with or without adjuvant (ISS, 10 microg/mouse or CT, 0,5 microg/mouse). M6 specific antibodies were measured by enzyme linked immunosorbent assay using class and subclass specific monoclonal antibodies. RESULTS: The use of ISS induced an impressive anti M-protein serum IgG response but when id administered was not detectable in the absence of adjuvant. When used in, M-protein in the presence of both ISS and CT induced anti M-protein IgA in the bronchoalveolar lavage, as well as specific IgG in the serum. IgG were able to react with serotype M6 strains of S. pyogenes. The level of antibodies obtained by immunizing mice in with M-protein and CT was higher in comparison to M-protein and ISS. The analysis of anti-M protein specific IgG subclasses showed high levels of IgG1, IgG2a and IgG2b, and low levels of IgG3 when ISS were used as adjuvant. Thus, in the presence of ISS, the ratio IgG2a/IgG1 and (IgG2a+IgG3)/IgG1 >1 indicated a type 1-like response obtained both in mucosally or systemically vaccinated mice. INTERPRETATION & CONCLUSION: Our study offers a reproducible model of anti-M protein vaccination that could be applied to test new antigenic formulations to induce an anti-group A Streptococcus (GAS) vaccination suitable for protection against the different diseases caused by this bacterium.

The interaction of human dendritic cells with yeast and germ-tube forms of Candida albicans leads to efficient fungal processing, dendritic cell maturation, and acquisition of a Th1 response-promoting function.

T helper cell type 1 (Th1) cell-mediated immunity plays a critical role in protection against the opportunistic pathogen Candida albicans. Virulence of the fungus is closely associated with its ability to form germ-tubes (GT), the early phase of the dimorphic transition from the commensal yeast (Y) to the more invasive hyphal (H) form. In this study, we examined the functional outcome of the interaction of Y or GT forms with human dendritic cells (DCs), professional antigen-presenting cells, which are pivotal for initiation and modulation of T cell responses. DCs phagocytosed and killed Y and GT cells with a comparable efficiency, becoming able to trigger strong proliferative responses by Candida-specific, autologous T cell clones. Both fungal forms induced DC maturation, as indicated by up-regulation of CD83, CD80, CD86, CD40, and major histocompatibility complex classes I and II surface antigens. Chemokine receptors were also modulated in Candida-DCs, which showed increased CCR7/CXCR4 and decreased CCR5 expression. Y- and GT-activated DCs differed in the pattern of cytokine expression. In particular, GT cells, in common with fully differentiated H cells, induced significantly more elevated levels of interleukin (IL)-10 than Y cells. Nevertheless, Y-, GT-, or H-pulsed DCs secreted comparable amounts of IL-12p70. In addition, irrespective of the fungal form triggering DC activation, Candida-DCs acquired the ability to prime naive T lymphocytes with a defined Th1 phenotype. Overall, our findings highlight the induction of substantially similar functional patterns in human DCs encountering the different forms of growth of C. albicans, both seemingly activating the Th1-type immunity which is characteristic of the healthy human subjects, naturally immunized and protected against the fungus.

Antigenic properties and processing requirements of 65-kilodalton mannoprotein, a major antigen target of anti-Candida human T-cell response, as disclosed by specific human T-cell clones.

T-cell-mediated immunity is known to play a central role in the host response to Candida albicans. T-cell clones are useful tools for the exact identification of fungal T-cell epitopes and the processing requirements of C. albicans antigens. We isolated human T-cell clones from an HLA-DRB1*1101 healthy donor by using an antigenic extract (MP-F2) of the fungus. Specific clones were T-cell receptor alpha/beta and CD4(+)/CD8(-) and showed a T-helper type 1 cytokine profile (production of gamma interferon and not interleukin-4). The large majority of these clones recognized both the natural (highly glycosylated) and the recombinant (nonglycosylated) 65-kDa mannoprotein (MP65), an MP-F2 minor constituent that was confirmed to be an immunodominant antigen of the human T-cell response. Surprisingly, most of the clones recognized two synthetic peptides of different MP65 regions. However, the peptides shared the amino acid motif IXSXIXXL, which may be envisaged as a motif sequence representing the minimal epitope recognized by these clones. Three clones recognized natural and pronase-treated MP65 but did not detect nonglycosylated, recombinant MP65 or the peptides, suggesting a possible role for polysaccharides in T-cell recognition of C. albicans. Finally, lymphoblastoid B-cell lines were efficient antigen-presenting cells (APC) for recombinant MP65 and peptides but failed to present natural, glycosylated antigens, suggesting that nonprofessional APC might be defective in processing highly glycosylated yeast proteins. In conclusion, this study provides the first characterization of C. albicans-specific human T-cell clones and provides new clues for the definition of the cellular immune response against C. albicans.

The adjuvant effect of synthetic oligodeoxynucleotide containing CpG motif converts the anti-Haemophilus influenzae type b glycoconjugates into efficient anti-polysaccharide and anti-carrier polyvalent vaccines.

Synthetic oligodeoxynucleotides containing CpG immunostimulatory sequences (ISS) have been shown to act as potent adjuvants of type 1 immune responses when co-administered with protein or peptide vaccines. We have recently shown that ISS can increase the anti-polysaccharide (CHO) and anti-tetanus toxoid (TT) or anti-diphtheria (CRM) toxoid antibody levels if used as adjuvant of anti-Haemophilus influenzae type b (Hib) CHO vaccine conjugated with TT or CRM. The analysis of anti-TT and anti-CRM IgG subclasses showed a significant increase in IgG2a, IgG2b and/or IgG3 in the presence of ISS. Anti-TT and anti-CRM antibodies were shown to neutralize the activity of both the tetanus and diphtheria toxin in vivo or in vitro tests respectively. These data show that ISS have the potential to increase host antibody response against both the CHO and the protein component of a conjugated vaccine, and encourage the investigation to identify strategies of vaccination with schedules aimed at the valuation of protein carriers as protective immunogens.

Synthetic oligodeoxynucleotide containing CpG motif induces an anti-polysaccharide type 1-like immune response after immunization of mice with Haemophilus influenzae type b conjugate vaccine.

Synthetic oligodeoxynucleotides containing CpG motifs [immunostimulatory sequences (ISS)] have been described as potent adjuvants of type 1 immune responses when co-administered with protein or peptide vaccines. To investigate their role in the immune response to polysaccharides (CHO), different preparations of anti-Haemophilus influenzae type b (Hib) conjugate vaccine were administered to mice. The unconjugated CHO did not induce the synthesis of specific antibodies even in the presence of ISS. On the other hand, anti-CHO-specific antibodies significantly increased in the presence of ISS, when tetanus (TT) or diphtheria [cross-reacting material (CRM)] toxoid-conjugated CHO were used to immunize mice. The adjuvant effect was also observed for the immune response against the carrier protein (TT and CRM). ISS insured an early and long-lasting specific IgG production. The effects of ISS on the anti-CHO immune response could be attributed to the amplification of the T help provided by the carrier. The analysis of anti-CHO IgG subclasses showed a significant increase of IgG2a and IgG3 in the presence of ISS. ISS caused a rapid release of IL-12 and IFN-gamma in sera from treated mice. This data provide a first evidence for the ability of ISS to induce an anti-CHO type 1-like immune response and demonstrate that ISS have the potential to increase host antibody response against both the CHO and the protein component of a conjugated vaccine.