Antigen-specific responses assessment for the evaluation of Bordetella pertussis T cell immunity in humans.

Measurement of antigen-specific T cell responses is an adjunctive parameter to evaluate protection induced by a previous Bordetella pertussis infection or vaccination. The assessment of T cell responses is technically complex and usually performed on fresh peripheral blood mononuclear cells (PBMC). The objective of this study was to identify simplified methods to assess pertussis specific T cell responses and verify if these assays could be performed using frozen/thawed (frozen) PBMC. Three read-outs to measure proliferation were compared: the fluorescent dye 5,6-carboxylfluorescein diacetate succinimidyl ester (CFSE) dilution test, the number of blast cells defined by physical parameters, and the incorporation of (3)H-thymidine. The results of pertussis-specific assays performed on fresh PBMC were compared to the results on frozen PBMC from the same donor. High concordance was obtained when the results of CFSE and blast read-outs were compared, an encouraging result since blast analysis allows the identification of proliferating cells and does not require any use of radioactive tracer as well as any staining. The results obtained using fresh and frozen PBMC from the same donor in the different T cell assays, including IFNγ and TNFα cytokine production, did not show significant differences, suggesting that a careful cryopreservation process of PBMC would not significantly influence T cell response evaluation. Adopting blast analysis and frozen PBMC, the possibility to test T cell responses is simplified and might be applied in population studies, providing for new instruments to better define correlates of protection still elusive in pertussis.

Phenotypic characteristics of human type II alveolar epithelial cells suitable for antigen presentation to T lymphocytes.

Type II alveolar epithelial cells (AECII) are well known for their role in the innate immune system. More recently, it was proposed that they could play a role in the antigen presentation to T lymphocytes but contradictory results have been published both concerning their surface expressed molecules and the T lymphocyte responses in mixed lymphocyte cultures. The use of either AECII cell line or fresh cells could explain the observed discrepancies. Thus, this study aimed at defining the most relevant model of accessory antigen presenting cells by carefully comparing the two models for their expression of surface molecules necessary for efficient antigen presentation.

Evaluation of tumor response, disease control, progression-free survival, and time to progression as potential surrogate end points in metastatic breast cancer.

PURPOSE: Overall survival (OS) can be observed only after prolonged follow-up, and any potential effect of first-line therapies on OS may be confounded by the effects of subsequent therapy. We investigated whether tumor response, disease control, progression-free survival (PFS), or time to progression (TTP) could be considered a valid surrogate for OS to assess the benefits of first-line therapies for patients with metastatic breast cancer. PATIENTS AND METHODS: Individual patient data were collected on 3,953 patients in 11 randomized trials that compared an anthracycline (alone or in combination) with a taxane (alone or in combination with an anthracycline). Surrogacy was assessed through the correlation between the end points as well as through the correlation between the treatment effects on the end points. RESULTS: Tumor response (survival odds ratio [OR], 6.2; 95% CI, 5.3 to 7.0) and disease control (survival OR, 5.5; 95% CI, 4.8 to 6.3) were strongly associated with OS. PFS (rank correlation coefficient, 0.688; 95% CI, 0.686 to 0.690) and TTP (rank correlation coefficient, 0.682; 95% CI, 0.680 to 0.684) were moderately associated with OS. Response log ORs were strongly correlated with PFS log hazard ratios (linear coefficient [rho], 0.96; 95% CI, 0.73 to 1.19). Response and disease control log ORs and PFS and TTP log hazard ratios were poorly correlated with log hazard ratios for OS, but the confidence limits of rho were too wide to be informative. CONCLUSION: No end point could be demonstrated as a good surrogate for OS in these trials. Tumor response may be an acceptable surrogate for PFS.

Normal IgG response to dermatophagoïde P1 antigen, bovin betalactoglobulin and soya protein

info:eu-repo/semantics/published

Impact of tumor board recommendations on treatment outcome for locally advanced head and neck cancer

Background/Aims: To identify physician selection factors in the treatment of locally advanced head and neck cancer and how treatment outcome is affected by Tumor Board recommendations. Methods: A retrospective analysis of 213 patients treated for locally advanced head and neck cancer in a single institution was performed. All treatments followed Tumor Board recommendations: 115 patients had chemotherapy and radiation, and 98 patients received postoperative radiation. Patient characteristics, treatment toxicity, locoregional control and survival between these two treat- ment groups were compared. Patient survival was compared with survival data reported in randomized studies of locally advanced head and neck cancer. Results: There were no differences in comorbidity factors, and T or N stages between the two groups. A statistically significant number of patients with oropharyngeal and oral cavity tumors had chemoradiation and postoperative radiation, respectively (p < 0.0001). Grade 3-4 toxicities during treatment were 48 and 87% for the postoperative radiation and chemoradiation groups, respectively (p = 0.0001). There were no differences in survival, locoregional recurrences and distant metastases between the two groups. Patient survival was comparable to survival rates reported by randomized studies of locally advanced head and neck cancer. Conclusion: Disease sites remained the key determining factor for treatment selection. Multidisciplinary approaches provided optimal treatment outcome for locally advanced head and neck cancer, with overall survival in these patients being comparable to that reported in randomized clinical trials. Copyright © 2008 S. Karger AG.

Normal IgG response to dermatophagoïde P1 antigen, bovine betalactoglobulin and soya proteins

info:eu-repo/semantics/published

Ontogeny of mouse B lymphocytes and inactivation by antigen of early B lymphocytes

Taking advantage of recent findings about membrane fluidity, the authors studied and compared the biosynthetic capacities of fetal or neonatal mouse B (bone marrow derived) lymphocytes (until 10 days after birth) and adult B lymphocytes. Although both early and adult lymphocytes can synthesize surface immunoglobulins, they have a different physiological behavior after interaction with a ligand (anti immunoglobulin sera or antigen), either in vivo or in vitro. Fetal and neonatal lymphocytes bearing surface immunoglobulins do not reexpress their membrane receptors after capping and endocytosis promoted by anti immunoglobulin sera. On the other hand, adult lymphocytes resynthesize completely their receptors after the same treatment. Furthermore, intrafetal injections of hemocyanin in pregnant mice lead to a striking decrease in the number of hemocyanin binding cells. It seems plausible that this non reexpression of surface immunoglobulins could be the first step in tolerance establishment.

Expression, purification and X-ray crystallographic analysis of the Helicobacter pylori blood group antigen-binding adhesin BabA

Helicobacter pylori is a human pathogen that colonizes about 50% of the world's population, causing chronic gastritis, duodenal ulcers and even gastric cancer. A steady emergence of multiple antibiotic resistant strains poses an important public health threat and there is an urgent requirement for alternative therapeutics. The blood group antigen-binding adhesin BabA mediates the intimate attachment to the host mucosa and forms a major candidate for novel vaccine and drug development. Here, the recombinant expression and crystallization of a soluble BabA truncation (BabA^25-460) corresponding to the predicted extracellular adhesin domain of the protein are reported. X-ray diffraction data for nanobody-stabilized BabA^25-460 were collected to 2.25Å resolution from a crystal that belonged to space group P21, with unit-cell parameters a = 50.96, b = 131.41, c = 123.40Å, α = 90.0, β = 94.8, γ = 90.0°, and which was predicted to contain two BabA^25-460-nanobody complexes per asymmetric unit.

Optimal kinetics for quantification of antigen-induced cytokines in human peripheral blood mononuclear cells by real-time PCR and by ELISA.

Real-time polymerase chain reaction (PCR) has recently been described as a new tool to measure and accurately quantify mRNA levels. In this study, we have applied this technique to evaluate cytokine mRNA synthesis induced by antigenic stimulation with purified protein derivative (PPD) or heparin-binding haemagglutinin (HBHA) in human peripheral blood mononuclear cells (PBMC) from Mycobacterium tuberculosis-infected individuals. Whereas PPD and HBHA optimally induced IL-2 mRNA after respectively 8 and 16 to 24 h of in vitro stimulation, longer in vitro stimulation times were necessary for optimal induction of interferon-gamma (IFN-gamma) mRNA, respectively 16 to 24 h for PPD and 24 to 96 h for HBHA. IL-13 mRNA was optimally induced by in vitro stimulation after 16-48 h for PPD and after 48 to 96 h for HBHA. Comparison of antigen-induced Th1 and Th2 cytokines appears, therefore, valuable only if both cytokine types are analysed at their optimal time point of production, which, for a given cytokine, may differ for each antigen tested. Results obtained by real-time PCR for IFN-gamma and IL-13 mRNA correlated well with those obtained by measuring the cytokine concentrations in cell culture supernatants, provided they were high enough to be detected. We conclude that real-time PCR can be successfully applied to the quantification of antigen-induced cytokine mRNA and to the evaluation of the Th1/Th2 balance, only if the kinetics of cytokine mRNA appearance are taken into account and evaluated for each cytokine measured and each antigen analysed.

Heparin-binding hemagglutinin, from an extrapulmonary dissemination factor to a powerful diagnostic and protective antigen against tuberculosis.

Interactions of Mycobacterium tuberculosis with macrophages have long been recognized to be crucial to the pathogenesis of tuberculosis. The role of non-phagocytic cells is less well known. We have discovered a M. tuberculosis surface protein that interacts specifically with non-phagocytic cells, expresses hemagglutination activity and binds to sulfated glycoconjugates. It is therefore called heparin-binding hemagglutinin (HBHA). HBHA-deficient M. tuberculosis mutant strains are significantly impaired in their ability to disseminate from the lungs to other tissues, suggesting that the interaction with non-phagocytic cells, such as pulmonary epithelial cells, may play an important role in the extrapulmonary dissemination of the tubercle bacillus, one of the key steps that may lead to latency. Latently infected human individuals mount a strong T cell response to HBHA, whereas patients with active disease do not, suggesting that HBHA is a good marker for the immunodiagnosis of latent tuberculosis, and that HBHA-specific Th1 responses may contribute to protective immunity against active tuberculosis. Strong HBHA-mediated immuno-protection was shown in mouse challenge models. HBHA is a methylated protein and its antigenicity in latently infected subjects, as well as its protective immunogenicity strongly depends on the methylation pattern of HBHA. In both mice and man, the HBHA-specific IFN-gamma was produced by both the CD4(+) and the CD8(+) T cells. Furthermore, the HBHA-specific CD8(+) T cells expressed bactericidal and cytotoxic activities to mycobacteria-infected macrophages. This latter activity is most likely perforin mediated. Together, these observations strongly support the potential of methylated HBHA as an important component in future, acellular vaccines against tuberculosis.

The mycobacterial heparin-binding hemagglutinin, virulence factor and antigen useful for diagnostics and vaccine development.

info:eu-repo/semantics/published

Persistence at one year of age of antigen-induced cellular immune responses in preterm infants vaccinated against whooping cough: comparison of three different vaccines and effect of a booster dose.

Due to their high risk of developing severe Bordetella pertussis (Bp) infections, it is recommended to immunize preterm infants at their chronological age. However, little is known about the persistence of their specific immune responses, especially of the cellular responses recognized to play a role in protection. We compared here the cellular immune responses to two major antigens of Bp between three groups of one year-old children born prematurely, who received for their primary vaccination respectively the whole cell vaccine Tetracoq(®) (TC), the acellular vaccine Tetravac(®) (TV), or the acellular vaccine Infanrix-hexa(®) (IR). Whereas most children had still detectable IFN-γ responses at one year of age, they were lower in the IR-vaccinated children compared to the two other groups. In contrast, both the TV- and the IR-vaccinated children displayed higher Th2-type immune responses, resulting in higher antigen-specific IFN-γ/IL-5 ratios in TC- than in TV- or IR-vaccinated children. The IFN-γ/IL-5 ratio of mitogen-induced cytokines was also lower in IR- compared to TC- or TV-vaccinated children. No major differences in the immune responses were noted after the booster compared to the pre-booster responses for each vaccine. The IR-vaccinated children had a persistently low specific Th1-type immune response associated with high specific Th2-type immune responses, resulting in lower antigen-specific IFN-γ/IL-5 ratios compared to the two other groups. We conclude that antigen-specific cellular immune responses persisted in one year-old children born prematurely and vaccinated during infancy at their chronological age, that a booster dose did not significantly boost the cellular immune responses, and that the Th1/Th2 balance of the immune responses is modulated by the different vaccines.

Different T cell memory in preadolescents after whole-cell or acellular pertussis vaccination.

To better understand vaccine-induced protection and its potential failure in light of recent whooping cough resurgence, we evaluated quantity as well as quality of memory T cell responses in B. pertussis-vaccinated preadolescent children. Using a technique based on flow cytometry to detect proliferation, cytokine production and phenotype of antigen-specific cells, we evaluated residual T cell memory in a cohort of preadolescents who received a whole-cell pertussis (wP; n=11) or an acellular pertussis vaccine (aP; n=13) during infancy, and with a median of 4 years elapsed from the last pertussis booster vaccine, which was aP for all children. We demonstrated that B. pertussis-specific memory T cells are detectable in the majority of preadolescent children several years after vaccination. CD4(+) and CD8(+) T cell proliferation in response to pertussis toxin and/or filamentous hemagglutinin was detected in 79% and 60% of the children respectively, and interferon-γ or tumor necrosis factor-α producing CD4(+) T cells were detected in 65% and 53% of the children respectively. Phenotyping of the responding cells showed that the majority of antigen-specific cells, whether defined by proliferation or cytokine production, were CD45RA(-)CCR7(-) effector memory T cells. Although the time since the last booster vaccine was significantly longer for wP-compared to aP-vaccinated children, their proliferation capacity in response to antigenic stimulation was comparable, and more children had a detectable cytokine response after wP- compared to aP-vaccination. This study supports at the immunological level recent epidemiological studies indicating that infant vaccination with wP induces longer lasting immunity than vaccination with aP-vaccines.

The heparin-binding haemagglutinin, a latency antigen useful for vaccine development

info:eu-repo/semantics/nonPublished

Early cellular immune response to a new candidate mycobacterial vaccine antigen in childhood tuberculosis

The search for novel vaccines against tuberculosis (TB) would benefit from in-depths knowledge of the human immune responses to Mycobacterium tuberculosis (Mtb) infection. Here, we characterised in a low TB incidence country, the immune responses to a new candidate vaccine antigen against TB, the heparin-binding haemagglutinin (HBHA), in young children in contact with an active TB case (aTB). Children with no history of BCG vaccination were compared to those vaccinated at birth to compare the initial immune responses to HBHA with secondary immune responses. Fifty-eight children with aTB and 76 with latent TB infection (LTBI) were included and they were compared to 90 non-infected children. Whereas Mtb-infected children globally secreted more interferon-gamma (IFN-γ) in response to HBHA compared to the non-infected children, these IFN-γ concentrations were higher in previously BCG-vaccinated compared to non-vaccinated children. The IFN-γ concentrations were similar in LTBI and aTB children, but appeared to differ qualitatively. Whereas the IFN-γ secretion induced by native methylated and recombinant non-methylated HBHA were well correlated for aTB, this was not the case for LTBI children. Thus, Mtb-infected young children develop IFN-γ responses to HBHA that are enhanced by prior BCG vaccination, indicating BCG-induced priming, thereby supporting a prime-boost strategy for HBHA-based vaccines. The qualitative differences between aTB and LTBI in their HBHA-induced IFN-γ responses may perhaps be exploited for diagnostic purposes.