The human in vitro anti-type 4 pneumococcal polysaccharide antibody response is regulated by suppressor T cells

Effectiveness, immunogenicity and safety of 23-valent pneumococcal polysaccharide vaccine revaccinations in the elderly: a systematic review

Background

In many industrialized countries routine vaccination with the 23-valent pneumococcal polysaccharide vaccine (PPSV-23) is recommended to prevent pneumococcal disease in the elderly. However, vaccine-induced immunity wanes after a few years, and there are controversies around revaccination with PPSV-23. Here, we systematically assessed the effectiveness and safety of PPSV-23 revaccination.

Method

We conducted a systematic literature review in MEDLINE, EMBASE, and Cochrane Central Register of Controlled Trials from inception to June 2015. We included all study types that compared effectiveness, immunogenicity and/or safety of PPSV-23 as a primary vs. a revaccination dose in persons aged 50 years and older. With respect to immunogenicity, we calculated the ratio of geometric mean antibody concentrations and opsonophagocytic indexes at identical time-points after primary and revaccination. Additionally, we compared rates and severity of adverse events (AEs) after primary and revaccination.

Results

We included 14 observational studies. 10 studies had a prospective design and analysed data on (i) the same individuals after a first and a second dose of PPSV-23 given 1 to 10 years later (n = 5) or (ii) two groups consisting of participants receiving PPSV-23 who were either vaccine-naïve or had received a first PPSV-23 dose 3 to 13 years earlier (n = 5). Three studies used electronic data bases to compare AEs after primary vs. revaccination doses of PPSV-23 after 1 to 10 years and one study had a cross-sectional design. Number of participants in the non-register-based and register-based studies ranged from 29 to 1414 and 360 to 316,000, respectively. 11 out of 14 included studies were at high risk of bias, three studies had an unclear risk of bias. None of the studies reported data on clinical effectiveness. Immunogenicity studies revealed that during the first two months antibody levels tended to be lower after revaccination as compared to primary vaccination. Thereafter, no obvious differences in antibody levels were observed. Compared to primary vaccination, revaccination was associated with an increased risk of local and systemic AEs, which, however, were usually mild and self-limiting. The risk and severity of AEs appeared to decrease with longer intervals between primary and revaccination.

Conclusion

Data comparing the effectiveness of primary vs. revaccination with PPSV-23 are still lacking, because there are no studies with clinical endpoints. Data from observational studies indicates that revaccination with PPSV-23 is likely to induce long-term antibody levels that are comparable to those after primary vaccination. Given the high disease burden and the waning of vaccine-induced immunity, revaccination with PPSV-23 could be considered in the elderly. The increased risk of local and systemic AEs can likely be mitigated when giving revaccination at least five years after the primary dose. Adequately powered randomized controlled trials using clinical endpoints are urgently needed.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-2040-y) contains supplementary material, which is available to authorized users.

A model of Neisseria meningitidis vaccine based on LPS micelles detoxified by synthetic antiendotoxin peptides

We describe a model of vaccine based on detoxified endotoxin (LPS) conserving the supramolecular structure of micelles. Detoxification of LPS from Neisseria meningitidis group A, strain A1 (LPS A1), has been achieved by complex formation with a synthetic anti-endotoxin peptide (SAEP 2) binding to the lipid A moiety of LPS A1 with high affinity. Following subcutaneous injection in SW mice, LPS A1/SAEP 2 complex induced high titers of boostable IgG antibodies against the immunotype determinants of LPS A1, cross-reactive with group B LPS in either purified or cell-associated form. These antibodies were able to functionally fix and activate homologous and heterologous species of complement after binding to LPS A1-coated sheep erythrocytes. None of the IgG antibodies induced were specific for lipid A or SAEP 2 and none of the IgG antibodies cross-reacted with heterologous LPS. The purified IgG polyclonal antibodies significantly inhibited serum TNF production in CD1 mice intravenously challenged by homologous but not heterologous LPS. The immunogenic properties of LPS A1/SAEP 2 complex, investigated by the kinetic, magnitude and sub-isotype composition of the polyclonal antibodies induced, were comparable to those of a glycoconjugate obtained by covalent binding of LPS A1, detoxified by SAEP 2, to BSA working as a T-cell dependent carrier protein. The results obtained suggest that LPS behaves in vivo as a T-cell dependent antigen. The strategy of properly delivering to the immune system of mammalians, non-toxic LPS fully expressing its supramolecular antigenic structure, represents a novel approach for development of a new generation of R- and S-LPS/SAEP complex-based vaccines for prophylaxis of specific Gram-negative infections leading to sepsis and endotoxemia.

Generation of antibody responses to pneumococcal capsular polysaccharides is independent of CD1 expression in mice

Streptococcus pneumoniae is a bacterial microorganism that frequently causes serious infection, particularly in children and the elderly. Protection against infection with S. pneumoniae is based mainly on the generation of antibodies to the pneumococcal capsular polysaccharides (caps-PS), but the mechanisms responsible for the generation of anticapsular antibodies remain incompletely understood. The aim of the present study was to evaluate the role of CD1-restricted T cells in the antibody response to caps-PS. When immunized with Pneumo23, wild-type mice and CD1 knockout mice on BALB/c and C57BL/6 backgrounds generated immunoglobulin M (IgM) and IgG antibody responses to soluble caps-PS that were comparable. Similar results were obtained after immunization with heat-inactivated S. pneumoniae. The IgM and IgG antibody response of wild-type mice to Pneumo23 was not affected by an antagonizing monoclonal anti-CD1 antibody treatment. In summary, our data provide evidence that the antibody response to caps-PS is generated independently of CD1 expression.

CD4+ T Lymphocytes Expressing CD40 Ligand Help the IgM Antibody Response to Soluble Pneumococcal Polysaccharides via an Intermediate Cell Type

Streptococcus pneumoniae causes serious infections in children, the elderly, and immunocompromised patients. Protection against infections with S. pneumoniae is mediated through Abs against the capsular polysaccharides (caps-PS). We previously showed that the murine Ab response to caps-PS is dependent on CD40-CD40L interaction. In the present paper, we addressed the question of whether the CD40-CD40L-mediated modulation of the anti-caps-PS immune reaction is the result of a direct interaction between B lymphocytes and T lymphocytes or of an indirect interaction. SCID/SCID mice reconstituted with B lymphocytes from wild-type mice did not mount anti-caps-PS Abs. SCID/SCID mice reconstituted with B lymphocytes from wild-type mice and CD4+ T lymphocytes from wild-type mice but not CD4+ T lymphocytes from CD40L knockout mice stimulated the anti-caps-PS Ab response. This indicated that CD4+ T lymphocytes stimulated the anti-caps-PS Ab response in a CD40L-dependent manner. SCID/SCID mice reconstituted with B lymphocytes from CD40 knockout mice and CD4+ T lymphocytes from wild-type mice generated an anti-caps-PS Ab response that could be inhibited by MR1, a blocking anti-CD40L Ab. These data indicated that CD4+ T lymphocytes stimulated the anti-caps-PS Ab response in an indirect way. Finally, lethally irradiated CD40 knockout mice reconstituted with bone marrow from wild-type mice mounted an anti-caps-PS Ab response that was comparable to the Ab response in wild-type mice, revealing that the required CD40 was on hemopoietic cells. In conclusion, we provide evidence that CD4+ T lymphocytes expressing CD40L stimulate the Ab response to soluble caps-PS by interacting with CD40-expressing non-B cells.

The human antibody response to pneumococcal capsular polysaccharides is dependent on the CD40-CD40 ligand interaction

Protection against infections with Streptococcus pneumoniae is mediated by antibodies against the capsular polysaccharides (caps-PS). Here we show that in in vitro experiments CD4+ T lymphocytes stimulate and CD8+ T lymphocytes inhibit the human anti-caps-PS antibody response. Using antagonistic anti-CD40 and antagonistic anti-CD40 ligand (CD40L) monoclonal antibodies, we showed that the CD4+ T lymphocyte-mediated stimulation is dependent on the CD40-CD40L interaction. The role of CD40L was further illustrated by the observation that CD4+ T lymphocytes obtained from a patient with hyper-IgM syndrome were unable to enhance the immune response to caps-PS. Furthermore, CD4+ T lymphocytes from cord blood, which did not express CD40L in response to stimulation with caps-PS, failed to stimulate the antibody response of adult B lymphocytes to caps-PS. These in vitro findings were confirmed by in vivo experiments in which SCID/SCID mice were reconstituted with human mononuclear cells. Furthermore, we showed that caps-PS induce production of IL-4, IL-6, IL-10, and IFN-gamma, and that this enhanced production was inhibited by blocking the CD40-CD40L interaction. This is the first demonstration that the human immune response to caps-PS, which is markedly regulated by T lymphocytes, is dependent on the CD40-CD40L interaction.

After chemotherapy, functional humoral response capacity is restored before complete restoration of lymphoid compartments

Chemotherapy has, besides the beneficial effects, several adverse effects. Suppression of the immune system is one of the most important problems. Infections caused by encapsulated bacteria like Streptococcus pneumoniae are responsible for a major part of infectious problems during and after treatment. The splenic marginal zone is essential in the initiation of an immune response to encapsulated bacteria. In this study, we analysed the effects of three different cytostatic agents on humoral immune responses. We found a reduced, but detectable immune response capacity at two days after treatment although the marginal zone B cell population is severely reduced at this time point. Twenty-four days after cessation of treatment, the immune response capacity was largely restored although lymphoid compartments were still not completely restored at that time point. Apparently, the presence of only few marginal zone B cells is sufficient to evoke a rise in antibody titres and although antibody titre increases are low, even small rises are most likely clinically relevant.

Effect of individual conjugate dose on immunogenicity of type 6B pneumococcal polysaccharide-N. meningitidis outer membrane protein complex conjugate vaccines in infant rhesus monkeys

A pneumococcal conjugate vaccine (PCV) has been developed consisting of capsular polysaccharide (Ps) coupled to the outer membrane protein complex of Neiserria meningitidis serogroup B. Experiments were conducted in infant rhesus monkeys to assess the potential to administer multiple Pn types in a single vaccine. A single type conjugate, 6B, was dosed from 0.025 to 25 microg Ps. Peak anti-6B Ps Ab titers were seen at lower doses of 0.025 and 0.25 microg Ps, while reduced titers of anti-6B Ps Ab were observed at the highest doses of conjugate administered, 2.5 and 25 microg Ps. By mixing free Ps, carrier, or another monovalent PCV with this 6B PCV, it was determined that reduced anti-6B Ps titers at high PCV doses were associated only with the quantity of type-specific Ps in the conjugate. Thus, increasing the amount of carrier protein or adding an additional monovalent conjugate did not significantly affect the response to type 6B Ps. These results suggest that, given an appropriately determined dose per individual pneumococcal Ps type, a multivalent PCV that includes many different types should have satisfactory clinical immunogenicity.

Humoral immune response to Klebsiella capsular polysaccharides in HLA-B27-positive patients with acute anterior uveitis and ankylosing spondylitis

Klebsiella is suggested to trigger ankylosing spondylitis (AS) and acute anterior uveitis (AAU) in HLA-B27-positive individuals. Previous investigations showed an increased antibody response to the Klebsiella capsular types K26, K36, and K50 in sera from HLA-B27-positive AS patients. In the present study the prevalence and titers of antibodies against Klebsiella capsular antigens were measured by means of an ELISA in 32 sera from HLA-B27-positive AAU patients either with (n = 10) or without AS (n = 22) and compared with sera from HLA-B27-negative AS-patients (n = 13). Sera from either HLA-B27-positive (n = 45) or negative (n = 40) healthy individuals served as control. Sera from HLA-B27-positive AAU with or without AS showed significantly higher antibody prevalence and IgG-titers against capsular antigens of the Klebsiella serotypes K26, K36, and K50 when compared with sera from HLA-B27-negative AS patients or with healthy controls. These results might be taken to indicate the predominance of these serotypes in the HLA-B27-associated AS and AAU.

Streptococcus pneumoniae: virulence factors, pathogenesis, and vaccines

Although pneumococcal conjugate vaccines are close to being licensed, a more profound knowledge of the virulence factors responsible for the morbidity and mortality caused by Streptococcus pneumoniae is necessary. This review deals with the major structures of pneumococci involved in the pathogenesis of pneumococcal disease and their interference with the defense mechanisms of the host. It is well known that protection against S. pneumoniae is the result of phagocytosis of invading pathogens. For this process, complement and anticapsular polysaccharide antibodies are required. Besides, relatively recent experimental data suggest that protection is also mediated by the removal of disintegrating pneumococci and their degradation products (cell wall, pneumolysin). These structures seem to be major contributors to illness and death caused by pneumococci. An effective conjugate vaccine should therefore preferably include the capsular polysaccharide and at least one of these inflammatory factors.

Comparison of the antibody responses to the 77 Klebsiella capsular types in ankylosing spondylitis and various rheumatic diseases

The production of antibodies to Klebsiella capsular polysaccharides was measured in sera from either HLA-B27-positive (HLA-B27+) or HLA-B27-negative (HLA-B27-) patients with classical ankylosing spondylitis (n = 54). These sera were compared with sera from patients with various rheumatic diseases (n = 82) and HLA-B27+ or HLA-B27- healthy individuals (n = 85). All sera were analyzed by means of an enzyme-linked immunosorbent assay specific to each of the 77 Klebsiella serotypes. The sera from HLA-B27+ patients with ankylosing spondylitis showed a significantly higher antibody frequency to the capsular types K26, K36, and K50 than the sera from HLA-B27- ankylosing spondylitis patients, patients with psoriatic arthritis, systemic lupus erythematosus, rheumatoid arthritis, or reactive arthritis after Yersinia enterocolitica infection, or healthy controls (P < 0.02). The antibodies were of the immunoglobulin G type. No significant antibody response to the other 74 Klebsiella serotypes, noncapsulated mutants of K26, K36, and K50, or preparations of Citrobacter, Serratia, Hafnia, or Morganella spp. or Streptococcus pneumoniae could be detected. The results might suggest a specific association between these capsular types and HLA-B27+ ankylosing spondylitis and might imply their predominance in this disease.

Serum antibodies to Klebsiella capsular polysaccharides in ankylosing spondylitis

OBJECTIVE

To measure antibodies to Klebsiella capsular polysaccharides in the sera of HLA-B27 positive patients with ankylosing spondylitis (AS), compared with HLA-B27 positive and HLA-B27 negative healthy control subjects.

METHODS

Antibodies were detected by means of an enzyme-linked immunosorbent assay specific for each of the 77 known Klebsiella serotypes.

RESULTS

Significantly elevated frequencies and titers of antibodies to capsular polysaccharides K26, K36, and K50 were detected in sera from AS patients, compared with controls.

CONCLUSION

These results suggest the predominance of Klebsiella serotypes K26, K36, and K50 in patients with AS.

Human B lymphocyte in vitro response to the group B streptococcal type III capsular carbohydrate

Anti-group B streptococcal type III polysaccharide-specific human B cells from the peripheral circulation can be activated and detected in an in vitro culture system. It is possible to detect both IgM- and IgG- producing cells from both seropositive and seronegative donors. The specificity of the response was demonstrated by inhibition with excess liquid phase antigen and the use of related but antigenically distinct control antigens. The response was absent without the addition of T cells, optimal at 10% and 25% T cells respectively for IgM- and IgG-secreting cells, and undetectable using 50% T cells. The optimal antigen concentration for in vitro B-cell activation is 2.5 x 10(-4) micrograms/ml. Cells from 5 of 6 seropositive donors and 3 of 7 seronegative donors produced specific IgM antibody after culture with antigen. We conclude that the control of the human antibody response to the group B streptococcal type III polysaccharide is influenced by T cells. The response seen in the culture system may be of value in assessing future vaccine candidates designed to prevent neonatal infections.

The amplifier role of T cells in the human in vitro B cell response to type 4 pneumococcal polysaccharide

The human B cell response to T cell independent type 2 antigens is regulated by thymus-derived lymphocytes. We analyzed the role of T cells in the in vitro antibody response to type 4 pneumococcal polysaccharide (PS4). We here show that the amplifying effect of T cells, which has previously been shown to be radioresistant and confined to T cell preparations enriched for CD4+ cells, is MHC non-restricted as demonstrated in cultures carried out in the presence of allogeneic T cells. Also, T cell clones derived from non-related donors are able to enhance the B cell response to PS4. All TCR alpha beta +, CD 4+ T cell clones, but none of the TCR alpha beta +, CD 8+ T cell clones tested, enhanced the B cell response to PS4. Furthermore, 3 out of 6 TCR gamma delta+ T cell clones were capable of enhancing the anti-PS4 B cell response. Experiments using recombinant lymphokines and glutaraldehyde-fixed T cells indicated that both lymphokines and T-B cell interactions are required for an optimal antibody response to PS4.

In Vitro Activation of Human T Lymphocytes by Haemophilus influenzae Type b Capsular Polysaccharides

Polyribosilribitolphosphate (PRP), the capsular polysaccharide from Haemophilus influenzae type b, is a T-cell-independent type 2 antigen. In vitro culture of adult peripheral blood T cells with 15 micrograms/ml PRP leads to induction of interleukin-2 receptor (IL-2R) expression on up to 10% of T cells. These cells are CD4+ and carry the alpha beta T-cell receptor. PRP, at concentrations above 1-5 micrograms/ml, can also induce in vitro proliferation of both adult and neonatal T cells. We conclude that PRP acts as a human T-cell mitogen. The in vitro proliferative response as well as IL-2R expression was studied in T cells derived from adults after vaccination with native PRP, with PRP conjugated to a carrier protein, or with diphtheria toxoid. Vaccination with conjugated PRP decreased the doses of PRP required for in vitro induction of IL-2R expression and T-cell proliferation. This indicates that vaccination with PRP conjugated to a carrier protein improves the in vitro T-cell response to PRP activation.