VaccHemInf project: protocol for a prospective cohort study of efficacy, safety and characterisation of immune functional response to vaccinations in haematopoietic stem cell transplant recipients

INTRODUCTION

Immune reconstitution after haematopoietic stem cell transplantation (HSCT) is a complex and dynamic process, varying from a state of nearly complete immunosuppression to an expected full immune recovery. Specific vaccination guidelines recommend reimmunisation after HSCT but data regarding vaccine efficacy in this unique population are scarce. New immune functional assays could enable prediction of vaccine response in the setting of HSCT.

METHODS AND ANALYSIS

A prospective, longitudinal single-centre cohort study of autologous and allogeneic HSCT recipients was designed in order to determine the vaccine response to five vaccine targets (pneumococcus, hepatitis B virus, Haemophilus Influenzae type b, tetanus and diphtheria) and to correlate it to immune function parameters. A workflow was set up to study serological response to vaccines and to describe the functional immune status of 100 HSCT recipients (50 autologous and 50 allogeneic) before and 3, 12 and 24 months after primary immunisation. At each time point, 'basic' immune status recording (serology, immunophenotyping of lymphocyte subsets by flow cytometry) will be assessed. The immune response will furthermore be evaluated before and 3 months after primary vaccination by two ex vivo immune functional assays assessing: (1) tumour necrosis factor alpha, interferon gamma production and host messenger RNA expression on whole-blood stimulation by lipopolysaccharide or Staphylococcus aureus enterotoxin B and (2) T-lymphocyte proliferation in response to a standard mitogen (phytohaemagglutinin) or to selected recall antigens. Reference intervals will be determined from a cohort of 30 healthy volunteers. This translational study will provide data describing vaccine response, immune functionality of HSCT recipients over time and will allow mapping HSCT recipients with regard to their immune function.

ETHICS AND DISSEMINATION

Ethical approval has been obtained from the institutional review board (no 69HCL17_0769). Results will be communicated at scientific meetings and submitted for publication in peer-reviewed journals.

TRIAL REGISTRATION NUMBER

NCT03659773; Pre-results.

The Effect of Differentially Designed Fusion Proteins to Elicit Efficient Anti-human Thyroid Stimulating Hormone Immune Responses

The production of human thyroid stimulating hormone (hTSH) immunoassays requires specific antibodies against hTSH which is a cumbersome process. Therefore, producing specific polyclonal antibodies against engineered recombinant fusion hTSH antigens would be of great significance. The best immunogenic region of the hTSH was selected based on in silico analyses and equipped with two different fusions. Standard methods were used for protein expression, purification, verification, structural evaluation, and immunizations of the white New Zealand rabbits. Ultimately, immunized serums were used for antibody titration, purification and characterization (specificity, sensitivity and cross reactivity). The desired antigens were successfully designed, sub-cloned, expressed, confirmed and used for in vivo immunization. Structural analyses indicated that only the bigger antigen has showed changed 2 dimensional (2D) and 3D structural properties in comparison to the smaller antigen. The raised polyclonal antibodies were capable of specific and sensitive hTSH detection, while the cross reactivity with the other members of the glycoprotein hormone family was minimum and negligible. The fusion which was solely composed of the tetanus toxin epitopes led to better protein folding and was capable of immunizing the host animals resulting into high titer antibody. Therefore, the minimal fusion sequences seem to be more effective in eliciting specific antibody responses.

A novel C3d-containing oligomeric vaccine provides insight into the viability of testing human C3d-based vaccines in mice

The use of C3d, the final degradation product of complement protein C3, as a "natural" adjuvant has been widely examined since the initial documentation of its immunogenicity-enhancing properties as a consequence of binding to complement receptor 2. Subsequently it was demonstrated that these effects are most evident when oligomeric, rather than when monomeric forms of C3d, are linked to various test protein antigens. In this study, we examined the feasibility of enhancing the adjuvant properties of human C3d further by utilizing C4b-binding protein (C4BP) to provide an oligomeric arrayed scaffold fused to the model antigen, tetanus toxin C fragment (TTCF). High molecular weight, C3d-containing oligomeric vaccines were successfully expressed, purified from mammalian cells and used to immunize groups of mice. Surprisingly, anti-TTCF antibody responses measured in these mice were poor. Subsequently we established by in vitro and in vivo analysis that, in the presence of mouse C3, human C3d does not interact with either mouse or even human complement receptor 2. These data confirm the requirement to develop murine versions of C3d based adjuvant compounds to test in mice or that mice would need to be developed that express both human C3 and human CR2 to allow the testing of human C3d based adjuvants in mouse in any capacity.

Conjugate Vaccines from Bacterial Antigens by Squaric Acid Chemistry: A Closer Look

By using O-SP-core (O-SPcNH2 ) polysaccharide, isolated from Vibrio cholera O1 lipopolysaccharide (LPS) and related synthetic substances, a detailed study of factors that affect conjugation of bacterial polysaccharides to protein carriers through squaric acid chemistry to form conjugate vaccines has been carried out. Several previously unrecognized processes that take place during the squarate labeling of the O-SPcNH2 and subsequent conjugation of the formed squarate (O-SPcNH-SqOMe) have been identified. The efficiency of conjugation at pH 8.5, 9.0, and 9.5 to bovine serum albumin (BSA) and to the recombinant tetanus toxin fragment C (rTT-Hc) has been determined. The study led to a protocol for more efficient labeling of O-SPcNH2 antigen with the methyl squarate group, to yield a higher-quality, more potent squarate conjugation reagent. Its use resulted in about twofold increases in conjugation efficiency (from 23-26 % on BSA to 51 % on BSA and 55 % on rTT-Hc). The spent conjugation reagent could be recovered and regenerated by treatment with MeI in the absence of additional base. The immunological properties of the experimental vaccine made from the regenerated conjugation reagent were comparable with those of the immunogen made from the parent O-SPcNH-SqOMe.

Durability of Vaccine-Induced Immunity Against Tetanus and Diphtheria Toxins: A Cross-sectional Analysis

BACKGROUND

Many adult immunization schedules recommend that tetanus and diphtheria vaccination be performed every 10 years. In light of current epidemiological trends of disease incidence and rates of vaccine-associated adverse events, the 10-year revaccination schedule has come into question.

METHODS

We performed cross-sectional analysis of serum antibody titers in 546 adult subjects stratified by age or sex. All serological results were converted to international units after calibration with international serum standards.

RESULTS

Approximately 97% of the population was seropositive to tetanus and diphtheria as defined by a protective serum antibody titer of ≥0.01 IU/mL. Mean antibody titers were 3.6 and 0.35 IU/mL against tetanus and diphtheria, respectively. Antibody responses to tetanus declined with an estimated half-life of 14 years (95% confidence interval, 11-17 years), whereas antibody responses to diphtheria were more long-lived and declined with an estimated half-life of 27 years (18-51 years). Mathematical models combining antibody magnitude and duration predict that 95% of the population will remain protected against tetanus and diphtheria for ≥30 years without requiring further booster vaccination.

CONCLUSIONS

These studies demonstrate that durable levels of protective antitoxin immunity exist in the majority of vaccinated individuals. Together, this suggests that it may no longer be necessary to administer booster vaccinations every 10 years and that the current adult vaccination schedule for tetanus and diphtheria should be revisited.

Tetanus neurotoxin HCC protein commits T cells to IFN-γ producing cells

A protective response against tetanus toxin and toxoid demands efficient specific T cell and B cell responses. Tetanus neurotoxin (TeNT), a 150 kDa polypeptide, is the main cause of tetanus disease. TeNT consists of two structurally distinct chains, a 50 kDa N-terminal light (L) and a 100 kDa C-terminal heavy (H) chain. C-terminal heavy (H) chain (fragment C) has two sub-domains named as proximal HCN and carboxy sub-domain or HCC. Beside neural binding property, HCC has been recently found as an immunodominant module of TeNT. In the present study, we investigated the effects of recombinant HCC (rHCC) on the expression of lineage specific transcription factors and secretion of a panel of functional cytokines including IFN-γ, IL-4, and IL-17 from purified human T cells. Our results revealed that T-bet transcript level, as TH1 specific transcription factor, was significantly increased in the cells treated with 10 and 20 µg/ml of rHCC following 48 h treatment(p<0.05). Treated purified human T cells with rHCC showed significant increase in IFN-γ mRNA level and cytokine secretion, but not IL-4 and IL-17, following 48 h treatment. In conclusion, our results showed that treatment of T cells with r HCC resulted in development of Th1 lineage phenotype, which might lead to a specific and protective antibody mediated response against tetanus toxin.

Design and construction of immune phage antibody library against Tetanus neurotoxin: Production of single chain antibody fragments

BACKGROUND

Tetanus neurotoxin (TeNT) is composed of a light (LC) and heavy chain (HC) polypeptides, released by anaerobic bacterium Clostridium tetani and can cause fatal life-threatening infectious disease. Toxin HC and LC modules represents receptor binding and zinc metalloprotease activity, respectively. The passive administration of animal-derived antibodies against tetanus toxin has been considered as the mainstay therapy for years. However, this treatment is associated with several adverse effects due to the presence of anti-isotype antibodies.

OBJECTIVE

In the present study, we have produced the fully human single chain antibody fragments (HuScFv) from two human antibody phage display libraries.

MATERIAL AND METHODS

Twenty-four different HuscFvs were isolated from two anti TeNT immune libraries. Our produced human ScFv (HuScFv) were converted to IgG platform and analyzed regarding their specific reactivity to TeNT.

RESULTS

All of the selected scFvs have the same VL but different VH. Three HuscFvs from the first library (TTX15, 51, 75) and two HuscFvs from the second library (TTX16, 20) were chosen to convert to IgG1 using pOptiVEC and pcDNA3.3 systems. Production of IgG1 from transfected DG44 and binding capacity of them to tetanus toxin and toxoid were measured by ELISA. ELISA results showed no detectable production of TTX16 and TTX20 IgG1. Although, TTX51 and TTX75 were converted and produced as IgG1, no reactivity to tetanus toxin and toxoid was observed. However, TTX15 was successfully produced as whole IgG1 platform with reactivity to both tetanus toxin and toxoid. The latter would be an appropriate replacement for conventional polyclonal antibodies if would meet the further characterization including specificity determination, affinity measurement and toxin neutralizing assays.

CONCLUSION

Our results demonstrated production of functional IgG1 derived from TTX15 scFv and might be an appropriate replacement for polyclonal Tetabulin but it needs further characterization.

[Evaluation of an immunochromatographic dipstick test for the assessment of tetanus immunity in horses]

Knowledge of tetanus immunity in equine patients is crucial in cases of injuries, elective surgeries, or when effective vaccination protocols are to be designed. The Fassisi® TetaCheck is a stall-side rapid test which was developed to address these issues. The purpose of the present study was to evaluate its performance parameters. To this end, the qualitative test results obtained by two blinded observers were compared to tetanus toxoid antibody levels from 99 serum samples, measured with a double antigen ELISA. Additionally the colour intensities of the test window were quantified using a camera and photo editing software. Assuming that the protective level of tetanus toxoid antibodies is ≥ 0.1 IE/ml, the tetanus quick stick (TQS) showed a sensitivity of 83.6% and a specificity of 100%. almost perfect (K = 0.88). Exchanging the observer did not affect the interpretation of theTQS (K = 0.80; K = 0.84). The definition of five distinct colour intensities of the "test window" enabled a clear differentiation of unprotected individuals from those with a protective immunity. There was a linear relationship between the objectively measured colour intensities and the tetanus toxoid antibody concentration (r2 = 0.74). The TQS thus proved to be a robust and reliable test in the stall-side assessment of tetanus immunity in horses. Its implementation in equine daily practice can help to avoid unnecessary immunizations in adult horses and therefore minimize vaccination side effects.

Diversity of the antibody response to tetanus toxoid: comparison of hybridoma library to phage display library

Monoclonal antibodies are important tools in research and since the 1990s have been an important therapeutic class targeting a wide variety of diseases. Earlier methods of mAb production relied exclusively on the lengthy process of making hybridomas. The advent of phage display technology introduced an alternative approach for mAb production. A potential concern with this approach is its complete dependence on an in vitro selection process, which may result in selection of V(H)-V(L) pairs normally eliminated during the in vivo selection process. The diversity of V(H)-V(L) pairs selected from phage display libraries relative to an endogenous response is unknown. To address these questions, we constructed a panel of hybridomas and a phage display library using the spleen of a single tetanus toxoid-immunized mouse and compared the diversity of the immune response generated using each technique. Surprisingly, the tetanus toxoid-specific antibodies produced by the hybridoma library exhibited a higher degree of V(H)-V(L) genetic diversity than their phage display-derived counterparts. Furthermore, the overlap among the V-genes from each library was very limited. Consistent with the notion that accumulation of many small DNA changes lead to increased antigen specificity and affinity, the phage clones displayed substantial micro-heterogeneity. Contrary to previous reports, we found that antigen specificity against tetanus toxoid is encoded by both V(κ) and V(H) genes. Finally, the phage-derived tetanus-specific clones had a lower binding affinity than the hybridomas, a phenomenon thought to be the result of random pairing of the V-genes.

Low seroprevalence of diphtheria, tetanus and pertussis in ambulatory adult patients: the need for lifelong vaccination

BACKGROUND

Tetanus, diphtheria, pertussis and measles are vaccine preventable diseases that have been reported to cause morbidity and mortality in adult population in the recent years. We aimed to document the seropositivity rates and vaccination indication for these four vaccine preventable diseases among adult and elderly patients who were seen as outpatients in a university hospital.

METHODS

Blood samples for tetanus, diphtheria, pertussis and measles antibodies were obtained. Results were evaluated with regards to protection levels and booster vaccine indications according to the cut-off values.

RESULTS

A total of 1367 patients consented for the study and 1303 blood samples were available for analysis at the end of the study. The antibody levels against measles conferred protection in 98% of patients. However, 65% of the patients had no protection for diphtheria, 69% had no protection for tetanus and 90% of the patients had no protection for pertussis. Only 1.3% of the study population had seropositivity against three of the diseases-Tdap booster was indicated in 98.7%. Multivariable logistic regression showed that tetanus protection decreased with increasing age. Having a chronic disease was associated with a lower rate of protective antibodies for pertussis.

CONCLUSIONS

We demonstrated very low rates of protection against three of the vaccine preventable diseases of childhood-diphtheria, pertussis and tetanus. Booster vaccinations are required in adult life in accordance with national and international adult vaccination guidelines. The concept of "lifelong vaccination" should be implemented and every encounter with the patient should be regarded as a chance for catch-up.

Immunogenicity, safety and reactogenicity of the 10-valent pneumococcal non-typeable haemophilus influenzae protein D conjugate vaccine (PHiD-CV) in Nigerian Infants: a randomised trial

AIMS AND OBJECTIVES

The immunogenicity, reactogenicity and safety of the 10- valent pneumococcal non-typeable Haemophilus influenzae protein D conjugate vaccine (PHiD-CV) were evaluated in a cohort of Nigerian infants included in a study conducted in Mali and Nigeria (ClinicalTrials.gov identifier: NCT00678301).

SUBJECTS AND METHODS

In this open, randomised, controlled study, 119 healthy infants received combined diphtheria-tetanus-whole-cell pertussis-hepatitis B/ Haemophilus influenzae type b vaccine (DTPw-HBV/Hib) and oral poliovirus vaccine (OPV) co-administered with PHiD-CV (PHiD-CV group) or without PHiD-CV (control group) at 6-10-14 weeks of age. Pneumococcal antibody responses and opsonophagocytic activity were measured and adverse events were recorded.

RESULTS

One month post-dose 3, for each of the vaccine pneumococcal serotypes, e"90.1% of PHiD-CV recipients had an antibody concentration e"0.2 ug/mL compared to < 9 % (except for serotypes 14 [32.4%] and 19F [27.8%]) in the control group. For each of the vaccine pneumococcal serotypes, e"90.6% of infants in the PHiD-CV group had an OPA titre e"8, compared to % 18% (except for serotype 7F [60.0%]) in the control group. Anti-protein D antibody geometric mean antibody concentrations were 2949.7 EL.U/mL in the PHiD-CV group and 68.9 EL.U/mL in the control group. For each DTPw-HBV/Hib antigen antibody seroprotection/seropositivity rates were e"94.4%. Tolerability was generally comparable between the PHiD-CV and control vaccination groups.

CONCLUSIONS

PHiD-CV co-administered with routine vaccines was immunogenic for all vaccine pneumococcal serotypes and protein D in Nigerian infants. Vaccine tolerability was generally comparable between the PHiD-CV and control groups. These results suggest PHiD-CV can be co-administered with other vaccines included in the National Programme on Immunisation.

[Preclinical studies of an adsorbed diphtheria-tetanus-pertussis vaccine (ADTP-vaccine) with acellular pertussis component]

AIM

Evaluate standardness of antigenic composition of pertussis component, completeness of sorption of pertussis, diphtheria and tetanus components, specific activity and safety of experimental series ofADTP-vaccine with acellular pertussis component (ADTaP-vaccine).

MATERIALS AND METHODS

The content of separate antigens (pertussis toxin, filamentous hemagglutinin and agglutinogens 1, 2, 3) in samples of acellular pertussis component of ADTaP-vaccine and completeness of sorption of pertussis component of ADTaP-vaccine were evaluated by using enzyme immunoassay. Completeness of sorption of diphtheria and tetanus components were determined in flocculation reaction and antitoxin-binding reactions, respectively. Protective activity ofADTaP-vaccine was studied in model ofmeningoencephalitis development in mice infected with Bordetella pertussis (strain 18323) neurotropic virulent culture, protective activity oftetanus component - by survival of mice after administration of tetanus toxin, protective activity of diphtheria component - by survival of guinea pigs after administration of diphtheria toxin. Safety of preparations was evaluated in tests of acute and chronic toxicity with carrying out pathomorphologic studies including immature animals.

RESULTS

All the studied experimental series ofADTaP-vaccine were standard by content of separate antigens of pertussis microbe. All the ADTaP-vaccine components were completely sorbed on aluminium hydroxide gel. By protective activity ADTaP preparations satisfied the WHO requirements. The preparations were non-toxic in acute and chronic toxicity and did not induce pathomorphologic changes including immature animals.

CONCLUSION

Experimental samples of ADTaP-vaccine by specific activity and safety satisfied WHO requirements.

Equivalent T cell epitope promiscuity in ecologically diverse human pathogens

Background

The HLA (human leukocyte antigen) molecules that present pathogen-derived epitopes to T cells are highly diverse. Correspondingly, many pathogens such as HIV evolve epitope variants in order to evade immune recognition. In contrast, another persistent human pathogen, Mycobacterium tuberculosis, has highly conserved epitope sequences. This raises the question whether there is also a difference in the ability of these pathogens’ epitopes to bind diverse HLA alleles, referred to as an epitope’s binding promiscuity. To address this question, we compared the in silico HLA binding promiscuity of T cell epitopes from pathogens with distinct infection strategies and outcomes of human exposure.

Methods

We used computer algorithms to predict the binding affinity of experimentally-verified microbial epitope peptides to diverse HLA-DR, HLA-A and HLA-B alleles. We then analyzed binding promiscuity of epitopes derived from HIV and M. tuberculosis. We also analyzed promiscuity of epitopes from Streptococcus pyogenes, which is known to exhibit epitope diversity, and epitopes of Bacillus anthracis and Clostridium tetani toxins, as these bacteria do not depend on human hosts for their survival or replication, and their toxin antigens are highly immunogenic human vaccines.

Results

We found that B. anthracis and C. tetani epitopes were the most promiscuous of the group that we analyzed. However, there was no consistent difference or trend in promiscuity in epitopes contained in HIV, M. tuberculosis, and S. pyogenes.

Conclusions

Our results show that human pathogens with distinct immune evasion strategies and epitope diversities exhibit equivalent levels of T cell epitope promiscuity. These results indicate that differences in epitope promiscuity do not account for the observed differences in epitope variation and conservation.

Immunotoxicity of perfluorinated alkylates: calculation of benchmark doses based on serum concentrations in children

BACKGROUND

Immune suppression may be a critical effect associated with exposure to perfluorinated compounds (PFCs), as indicated by recent data on vaccine antibody responses in children. Therefore, this information may be crucial when deciding on exposure limits.

METHODS

Results obtained from follow-up of a Faroese birth cohort were used. Serum-PFC concentrations were measured at age 5 years, and serum antibody concentrations against tetanus and diphtheria toxoids were obtained at age 7 years. Benchmark dose results were calculated in terms of serum concentrations for 431 children with complete data using linear and logarithmic curves, and sensitivity analyses were included to explore the impact of the low-dose curve shape.

RESULTS

Under different linear assumptions regarding dose-dependence of the effects, benchmark dose levels were about 1.3 ng/mL serum for perfluorooctane sulfonic acid and 0.3 ng/mL serum for perfluorooctanoic acid at a benchmark response of 5%. These results are below average serum concentrations reported in recent population studies. Even lower results were obtained using logarithmic dose-response curves. Assumption of no effect below the lowest observed dose resulted in higher benchmark dose results, as did a benchmark response of 10%.

CONCLUSIONS

The benchmark dose results obtained are in accordance with recent data on toxicity in experimental models. When the results are converted to approximate exposure limits for drinking water, current limits appear to be several hundred fold too high. Current drinking water limits therefore need to be reconsidered.

[Construction and expression of recombinant prokaryotic expression vector for disulfide-stabilized anti-TeNT single-chain Fv antibody]

OBJECTIVE

To construct the prokaryotic expression vector for disulfide-stabilized anti-TeNT single-chain Fv antibody (27G-scdsFv), express the 27G-scdsFv and characterize its bioactivity.

METHODS

27G-scdsFv gene was constructed by PCR-based point mutagenesis strategy and cloned into plasmid pET22b(+). The plasmid was then transformed into E.coli BL21(DE3) competent cells. The target protein was expressed under the induction of IPTG. SDS-PAGE and Western blotting were used to identify the expression products. The specific binding activity to TeNT-Hc and relative stability in vitro of 27G-scdsFv were assayed by ELISA, and the affinity of the antibody was measured by non-competitive enzyme-linked immunosorbentassay. The method of immunofluorescence was employed to determine whether or not the 27G-scdsFv kept the neutralizing activity in vitro.

RESULTS

Sequencing analysis proved that 27G-scdsFv gene was correctly constructed. The target protein was expressed in the form of inclusion body, accounting for about 50% of total bacterial proteins. After renaturated, the 27G-scdsFv protein still maintained specific binding activity to TeNT-Hc, with a higher affinity constant (K(D);) of 0.93×10(-7); mol/L as compared with that of 27G-scFv, and the yield of the protein was about 5 mg/L induced culture. The relative stability of 27G-scdsFv was improved obviously as compared with the scFv form. 27G-scdsFv strongly inhibited the binding of TeNT-Hc to PC-12 in vitro.

CONCLUSION

The porkaryotic expression vector of 27G-scdsFv has been successfully constructed and the activated target protein has been obtained, which lays a foundation for the further study on the biological function of 27G-scdsFv.

Innate interferons inhibit allergen and microbial specific T(H)2 responses

Several studies provided evidence of innate interferons (IFNs) regulating T(H)2 cytokine production using purified CD4(+) memory cells and T(H)2 polarisation via interleukin-4 (IL-4). Vitally, none of these previous studies examined IFN attenuation of T(H)2 responses to allergen or antigen. This study therefore sought to investigate the abrogation of specific allergen- and antigen-stimulated T(H)2 response in peripheral blood mononuclear cells (PBMC) derived from 12 sensitised individuals by IFN-β and IFN-λ. PBMC were cultured in the presence of house dust mite (HDM) allergen, rhinovirus (RV), influenza vaccine and tetanus toxoid (TT)±either IFN-β or IFN-λ for 3 and 5 days. IFN-γ, IL-5 and IL-13 protein levels were measured by ELISA. Quantitative PCR (qPCR) was used to investigate induction of genes involved in control of T(H)2 cytokines. No alteration in T(H)1 IFN-γ allergen/antigen response was observed with addition of IFN-β or IFN-λ. Consistent abrogation of T(H)2 response to HDM and influenza was observed with IFN-β at both time points; attenuation was observed by day 5 with RV and TT. IFN-λ had no consistent effect on T(H)2 production except in the presence of RV (multiplicity of infection=5); a decrease in IL-5 alone was observed in the presence of trivalent inactivated influenza vaccine. GATA binding protein 3 (GATA3) and suppressors of cytokine signalling3 mRNA were differentially regulated in HDM and influenza-stimulated cultures±IFN-β. We concluded that IFN-β produced a strong and consistent abrogation of T(H)2 cytokine production in the presence of a range of allergen and antigen stimulants.

Production, characterization and applications of a tetanus toxin specific monoclonal antibody T-62

Tetanus neurotoxin (TeNT) represents a potent toxin that binds to its receptors on neurons and inhibits the release of neurotransmitters. Additionally, its fragments are used to transport pharmacological substances to neuronal cell bodies. The main objective of this study was the development of a suitable model system to study internalization of the TeNT. We have produced a monoclonal antibody (MoAb) specific for TeNT by hybridoma technology, after immunization of BALB/c mice with tetanus toxoid, and have named it T-62. The immunochemical characteristics of MoAb T-62 were tested using ELISA, PAGE and immunoblotting. Finally, we have used an immunohistochemical method to detect specific binding of MoAb T-62 to TeNT bound to PC 12 cells. Our results show that MoAb T-62 is highly specific for TeNT, even when it is bound to its receptor, and that it could be of considerable importance in studies regarding fundamental research on TeNT receptors, intracellular transport of TeNT, as well as retrograde transport of pharmaceutical substances and non-invasive delivery of polypeptides through the blood brain barrier. In addition, MoAb T-62 is an invaluable tool in TeNT vaccine production as it can be used for the detection of reverse toxicity, which could drastically reduce the need to use animals in these experiments.

Immunity after (re)vaccination of paediatric patients following haematopoietic stem cell transplantation

AIMS

Loss of specific immunity follows allogeneic haematopoietic stem cell transplantation (HSCT) in the majority of cases. Responses to (re)vaccinations can be used as indicators of a functional immunological recovery.

METHODS

Twenty-three paediatric recipients of HSCT were enrolled in a single centre setting and responses to scheduled immunizations analysed.

RESULTS

Immunity to vaccine-preventable diseases was impaired post HSCT, but (re)vaccinations induced protective responses in 59-100%, depending on the vaccine, regardless of prior graft-versus-host disease (GVHD) history.

CONCLUSION

Despite the marked impact of moderate to severe chronic prior GVHD on both the qualitative and quantitative T-cell recovery post allogenic HSCT, most paediatric recipients of allogeneic stem cell grafts appear to attain protective antibody levels after immunization.

The inhibition of anti-DNA binding to DNA by nucleic acid binding polymers

Antibodies to DNA (anti-DNA) are the serological hallmark of systemic lupus erythematosus (SLE) and can mediate disease pathogenesis by the formation of immune complexes. Since blocking immune complex formation can attenuate disease manifestations, the effects of nucleic acid binding polymers (NABPs) on anti-DNA binding in vitro were investigated. The compounds tested included polyamidoamine dendrimer, 1,4-diaminobutane core, generation 3.0 (PAMAM-G3), hexadimethrine bromide, and a β-cylodextrin-containing polycation. As shown with plasma from patients with SLE, NABPs can inhibit anti-DNA antibody binding in ELISA assays. The inhibition was specific since the NABPs did not affect binding to tetanus toxoid or the Sm protein, another lupus autoantigen. Furthermore, the polymers could displace antibody from preformed complexes. Together, these results indicate that NABPs can inhibit the formation of immune complexes and may represent a new approach to treatment.

Expression of HLA class II molecules in humanized NOD.Rag1KO.IL2RgcKO mice is critical for development and function of human T and B cells

BACKGROUND

Humanized mice able to reconstitute a surrogate human immune system (HIS) can be used for studies on human immunology and may provide a predictive preclinical model for human vaccines prior to clinical trials. However, current humanized mouse models show sub-optimal human T cell reconstitution and limited ability to support immunoglobulin class switching by human B cells. This limitation has been attributed to the lack of expression of Human Leukocyte Antigens (HLA) molecules in mouse lymphoid organs. Recently, humanized mice expressing HLA class I molecules have been generated but showed little improvement in human T cell reconstitution and function of T and B cells.

METHODS

We have generated NOD.Rag1KO.IL2RγcKO mice expressing HLA class II (HLA-DR4) molecules under the I-E(d) promoter that were infused as adults with HLA-DR-matched human hematopoietic stem cells (HSC). Littermates lacking expression of HLA-DR4 molecules were used as control.

RESULTS

HSC-infused HLA-DR4.NOD.Rag1KO.IL-2RγcKO mice developed a very high reconstitution rate (>90%) with long-lived and functional human T and B cells. Unlike previous humanized mouse models reported in the literature and our control mice, the HLA-DR4 expressing mice reconstituted serum levels (natural antibodies) of human IgM, IgG (all four subclasses), IgA, and IgE comparable to humans, and elicited high titers of specific human IgG antibodies upon tetanus toxoid vaccination.

CONCLUSIONS

Our study demonstrates the critical role of HLA class II molecules for development of functional human T cells able to support immunoglobulin class switching and efficiently respond to vaccination.

[Production and immunogenicity analysis of conformation-stable fragment-C mutant of tetanus toxin]

Tetanus is caused by tetanus toxin synthesized by Clostridium tetani. Fragment C (Hc), the 50 kDa carboxy-terminal portion of tetanus toxin, is nontoxic but has receptor protein binding activities, which has been evaluated as a potential new recombinant subunit vaccine to replace the traditional formaldehyde inactivated toxoid vaccine. It is easy for wild Hc (HcW) to form inter- and intra-molecular disulfide bonds and the different conformations changes unstably, which brings difficulties for vaccine production technology. In our study, the Cys 869 of HcW was mutated to A1a and the conformation-stable fragment-C mutant of tetanus toxin (HcM) was constructed. The HcM was expressed, fermented and purified and its stability, receptor binding and immunogenicity were evaluated. The result showed that the HcM got high-level expression and was purified to > 95% of purity. The purified HcM was conformation-stable at different temperature for different time and kept the binding activities with one of its receptor GT1b. Mice given three vaccinations by HcM developed a protective immune response and were 100% protected against an intraperitoneal administration of 1 x 10(3) 50% lethal doses (LD50s) of tetanus neurotoxin. All the results showed that the conformation-stable HcM had potent immunogenicity as a recombinant tetanus vaccine candidate with simple production process and similar immunogenicity with HcW. Whether for routine tetanus therapy or for countries to respond to unexpected events (war, earthquake or other disaster), it is of great significance.

Potentiation of Immune Response from Polymer-Entrapped Antigen: Toward Development of Single Dose Tetanus Toxoid Vaccine

Poly(lactide) (PLA) polymer particles entrapping immunoreactive tetanus toxoid (TT) were used for generation of immune response using single point immunization. Immunization with different sizes of polymer particles encapsulating immunoreactive TT elicited anti-TT antibody titers that persisted for more than 5 months. However, antibody response generated by single point immunization of either nanoparticles or microparticles were lower than the conventional two doses of alum adsorbed TT. To overcome this limitation, alum was used with particles that improved anti-TT antibody response. Immunization with nanoparticles along with alum resulted in very high and early immune response: high anti-TT antibody titers were detected as early as 15 days postimmunization. However anti-TT antibody titers declined rapidly with time. Immunization with admixture of microparticles and alum elicited higher antibody titers than the particles alone and the antibody titers were high particularly during the later part of the postimmunization period. Single point immunization with admixture of PLA microparticles and alum resulted in an antibody response very close to that achieved by two injection of alum-adsorbed TT. Physical mixture of both a nano- and microparticles along with alum resulted in sustained anti-TT antibody response from very early days of postimmunization until 150 days. The antibody titers were maintained around 50 microg/ml for more than 5 months. These results indicated that immune response from polymer particles can be further improved by use of additional adjuvant. Furthermore, using various size particles or physical mixture of different size particles along with alum, it is possible to modulate the kinetics of immune response using polymer particles based immunization.

Immune response to fused core protein of hepatitis C virus and truncated tetanus toxin peptides in mice

Because no vaccine or effective therapy is available, thousands of people with HCV have died in recent years. Cytotoxic T lymphocytes (CTLs) play a critical role in the host cellular immune response against HCV. CTL epitopes in HCV core protein have been identified and used in vaccine development. T helper epitopes could promote cytokine secretion and antibody production to fight HCV. Tetanus toxin, an immunogen with many T helper epitopes, was once used in HBV therapeutic vaccine design. Here, eukaryotic and prokaryotic expression vectors were constructed to express truncated fragments of tetanus toxin and core genes of HCV. HLAA2.1 transgenic mice were inoculated with a recombinant plasmid vehicle with these two heterogenic gene fragments, and this augmented the titres of antibody against HCV. Antigen-specific lymphocyte proliferation, Th1 and Th2 cytokine levels and the number of lysed cells were markedly increased in the combined immunization group compared to controls. These findings provide new insights into a potential role for T helper epitopes from tetanus toxin combined with protein from the HCV core gene, which has numerous CTL epitopes. This design strategy may aid in the development of new vaccines against HCV.

Human monoclonal ScFv that inhibits cellular entry and metalloprotease activity of tetanus neurotoxin

Tetanus is a deadly disease of warm blooded animals and humans caused by an exotoxin called tetanospasmin or tetanus neurotoxin (TeNT) produced by anaerobic bacterium named Clostridium tetani TeNT is an A-B toxin; each molecule consists of a heavy chain (HC) containing cellular receptor binding domain and a light chain (LC) with zinc metalloprotease activity. TeNT produced in the infected tissue by the bacteria grown under anaerobic condition binds to ganglioside receptors of peripheral nerve, and endocytosed. The A subunit exits from the endosome and undergoes a retrograde transport via the nerve axon to the spinal cord. This highly toxic enzyme specifically cleaves one of the nerve cell SNARE proteins, i.e., synaptobrevin, resulting in inhibition of the release of neurotransmitters (glycine and GABA) from inhibitory interneuron causing spastic paralysis, the characteristic of tetanus. Current treatment mainstay of human tetanus is by passively administering anti-tetanus toxin produced from animals immunized with adjuvanted tetanus toxoid (TT). There are several obstacles in production and use of the animal derived therapeutic antibody especially the allergic reaction and serum sickness induced by the host immune response to the foreign protein. The animal antibody, mainly IgG, blocks nerve cell entry of the TeNT but does not neutralize the TeNT protease activity per se and cannot reverse the tetanus symptoms. In this study, fully human single chain antibody fragments (HuScFv) were produced from a human antibody phage display library. TT was used as antigen in a single round phage bio-panning to select phage clones that display TT bound-HuScFv from the library. HuScFv from 4 selected huscfv-phagemid transformed E. coli clones inhibited binding of the native TeNT to retinoic acid pulsed human neuroblastoma cells when used at the molecular TeNT:HuScFv ratio of 1:100. HuScFv from one of the 4 clones also inhibited the TeNT mediated cleavage of recombinant synaptobrevin. Further investigation is needed for identification of epitope specificity of these HuScFv and HuScFv effector mechanisms towards the TeNT. Cell penetrating version of the HuScFv that inhibited the TeNT zinc metalloprotease activity should be made. The HuScFv produced in this study either singly or in their suitable combination warrant developing further to a real use in humans as a surrogate of the animal antibody for treatment of tetanus.

Generation of plant-derived recombinant DTP subunit vaccine

The current diphtheria-tetanus-pertussis (DTP) pediatric vaccine is produced from the corresponding pathogenic bacteria Corynebacterium diphtheriae, Clostridium tetani and Bordetella pertussis; five injected doses of DTaP (acellular) vaccine are required for every child in the standard US vaccination schedule. Because the vaccine is derived from native live sources, adverse effects are possible and production is complex and costly. To address issues of safety, ease of renewability and expense, we used recombinant technology in an effort to develop a subunit DPT vaccine derived in non-pathogenic plant expression systems. Expression of diphtheria toxin (DT), tetanus fragment-C (TetC) and the non-toxic S1 subunit of pertussis toxin (PTX S1) antigenic proteins in soluble form in low-alkaloid tobacco plants and carrot cell cultures allowed efficient downstream purification to levels suitable for intramuscular injection in BALB/c mice. At working concentrations of 5mug per dose, these preparations induced high levels of antigen-specific IgGs in mouse sera. Our results clearly support the feasibility of producing recombinant pediatric vaccine components in plants.

Expression of a multi-epitope DPT fusion protein in transplastomic tobacco plants retains both antigenicity and immunogenicity of all three components of the functional oligomer

Expression of genes in plant chloroplasts provides an opportunity for enhanced production of target proteins. We report the introduction and expression of a fusion DPT protein containing immunoprotective exotoxin epitopes of Corynebacterium diphtheriae, Bordetella pertussis, and Clostridium tetani in tobacco chloroplasts. Using biolistic-mediated transformation, a plant-optimized synthetic DPT gene was successfully transferred to tobacco plastomes. Putative transplastomic T0 plants were identified by PCR, and Southern blot analysis confirmed homoplasmy in T1 progeny. ELISA assays demonstrated that the DPT protein retained antigenicity of the three components of the fusion protein. The highest level of expression in these transplastomic plants reached 0.8% of total soluble protein. To assess whether the functional recombinant protein expressed in tobacco plants would induce specific antibodies in test animals, a mice feeding experiment was conducted. For mice orally immunized with freeze-dried transplastomic leaves, production of IgG and IgA antibodies specific to each toxin were detected in serum and mucosal tissues.

Fit for purpose? A case study: validation of immunological endpoint assays for the detection of cellular and humoral responses to anti-tumour DNA fusion vaccines

Clinical trials are governed by an increasingly stringent regulatory framework, which applies to all levels of trial conduct. Study critical immunological endpoints, which define success or failure in early phase clinical immunological trials, require formal pre-trial validation. In this case study, we describe the assay validation process, during which the sensitivity, and precision of immunological endpoint assays were defined. The purpose was the evaluation of two multicentre phase I/II clinical trials from our unit in Southampton, UK, which assess the effects of DNA fusion vaccines on immune responses in HLA-A2+ patients with carcinoembryonic antigen (CEA)-expressing malignancies and prostate cancer. Validated immunomonitoring is being performed using ELISA and IFNgamma ELISPOTs to assess humoral and cellular responses to the vaccines over time. The validated primary endpoint assay, a peptide-specific CD8+ IFNgamma ELISPOT, was tested in a pre-trial study and found to be suitable for the detection of low frequency naturally occurring CEA- and prostate-derived tumour-antigen-specific T cells in patients with CEA-expressing malignancies and prostate cancer.

Induction of T cell-mediated immunity using a c-Myb DNA vaccine in a mouse model of colon cancer

Overexpression of the proto-oncogene c-Myb occurs in more than 80% of colorectal cancer (CRC) and is associated with aggressive disease and poor prognosis. To test c-Myb as a therapeutic target in CRC we devised a DNA fusion vaccine to generate an anti-CRC immune response. c-Myb, like many tumor antigens, is weakly immunogenic as it is a "self" antigen and subject to tolerance. To break tolerance, a DNA fusion vaccine was generated comprising wild-type c-Myb cDNA flanked by two potent Th epitopes derived from tetanus toxin. Vaccination was performed targeting a highly aggressive, weakly immunogenic, subcutaneous, syngeneic, colon adenocarcinoma cell line MC38 which highly expresses c-Myb. Prophylactic intravenous vaccination significantly suppressed tumor growth, through the induction of anti-tumor immunity for which the tetanus epitopes were essential. Vaccination generated anti-tumor immunity mediated by both CD4+ and CD8+ T cells and increased infiltration of immune effector cells at the tumor site. Importantly, no evidence of autoimmune pathology in endogenous c-Myb expressing tissues was detected as a consequence of breaking tolerance. In summary, these results establish c-Myb as a potential antigen for immune targeting in CRC and serve to provide proof of principle for the continuing development of DNA vaccines targeting c-Myb to bring this approach to the clinic.

Measuring immunoglobulin g antibodies to tetanus toxin, diphtheria toxin, and pertussis toxin with single-antigen enzyme-linked immunosorbent assays and a bead-based multiplex assay

Bead-based assay systems offer the possibility of measuring several specific antibodies in one sample simultaneously. This study evaluated a vaccine panel of a multianalyte system that measures antibodies to tetanus toxin, diphtheria toxin, and pertussis toxin (PT) from Bordetella pertussis. The antibody concentrations of human immunoglobulin G (IgG) to PT, tetanus toxin, and diphtheria toxin were measured in 123 serum pairs (total of 246 sera) from a vaccine study. The multianalyte bead assay was compared to a standardized in-house IgG- anti-PT enzyme-linked immunosorbent assay (ELISA) of the German reference laboratory for bordetellae, as well as to various commercially available ELISAs for anti-PT IgG, anti-tetanus IgG, and anti-diphtheria IgG. The results of the multiplex assay regarding the antibodies against diphtheria toxin compared favorably with a regression coefficient of 0.938 for values obtained with an ELISA from the same manufacturer used as a reference. Similarly, antibodies to tetanus toxin showed a correlation of 0.910 between the reference ELISA and the multianalyte assay. A correlation coefficient of 0.905 was found when an "in-house" IgG anti-PT and the multiplex assay were compared. Compared to single ELISA systems from two other manufacturers, the multiplex assay performed similarly well or better. The multianalyte assay system was a robust system with fast and accurate results, analyzing three parameters simultaneously in one sample. The system was well suited to quantitatively determine relevant vaccine induced antibodies compared to in-house and commercially available single-antigen ELISA systems.

[Gene cloning, optimized expression and immunogenicity evaluation of tetanus toxin fragment C]

OBJECTIVE

To obtain highly purified tetanus toxin fragment C (TTC) with good immunogenicity.

METHODS

The gene fragment encoding TTC was amplified from Clostridium tetani plasmid DNA by PCR, inserted into the vector pET43.1a (+) and expressed in E. coli BL21(DE3)plysS. After purification using Ni2+-chelate affinity chromatography, the expressed fusion protein was digested by thrombin and the resultant TTC protein was purified with Ni2+-chelate affinity chromatography followed by identification with SDS-PAGE and Western blotting. The purifed TTC protein was then used to immunize mice to test its immunogenecity.

RESULTS

The 1373-bp gene fragment encoding TTC was obtained, and the constructed recombinant expression vector pET43.1a (+)-TTC was successfully expressed in E. coli BL21(DE3)plysS. SDS-PAGE identified a recombinant fusion protein with relative molecular mass (Mr) of 117 000, which accounted for 22% of the total bacterial protein. The TTC protein with Mr of 50 000 was obtained after purification of the thrombin digestion products of the fusion protein, with a purity reaching 95.5%. Both the fusion protein and TTC protein could be recognized by anti-tetanus toxin antibody as shown by Western blotting. The titer of the anti-serum from mice immunized with the TTC protein was 1:25 600, and the anti-serum could specifically bind to tetanus toxin.

CONCLUSION

Highly purified and immunogenetic TTC protein has been successfully obtained, which provides a good model antigen for studying antigen presentation and immune responses in vivo.

Myostatin DNA vaccine increases skeletal muscle mass and endurance in mice

Myostatin is a transforming growth factor-beta family member that acts as a negative regulator of skeletal muscle growth. In mice, genetic disruption of the myostatin gene leads to a marked increase in body weight and muscle mass. Similarly, pharmacological interference with myostatin in vivo in mdx knockout mice results in a functional improvement of the dystrophic phenotype. Consequently, myostatin is an important therapeutic target for treatment of diseases associated with muscle wasting. To construct a therapeutic DNA vaccine against myostatin, we coupled the foreign, immunodominant T-helper epitope of tetanus toxin to the N terminus of myostatin, and BALB/c mice were immunized with the recombinant vector. Sera from vaccinated mice showed the presence of specific antibodies against the recombinant protein. In addition, body weight, muscle mass, and grip endurance of vaccinated mice were significantly increased. Our study provides a novel, pharmacological strategy for treatment of diseases associated with muscle wasting.

Tetramer-guided epitope mapping reveals broad, individualized repertoires of tetanus toxin-specific CD4+ T cells and suggests HLA-based differences in epitope recognition

Tetanus toxoid is a routine positive control antigen for cellular assays. Previous studies identified multiple tetanus toxin (TT) epitopes, including some 'universal' epitopes. However, rigorous HLA-restricted study of tetanus toxoid responses is still lacking. In this study, the tetramer-guided epitope mapping approach was used to identify CD4+ T-cell epitopes within the TT heavy chain restricted by 10 different class II alleles. Of 106 peptides tested, 52 contained epitopes. Response frequencies toward specific epitopes varied, indicating prevalent and rare specificities. Most antigenic peptides (85%) were presented by one or two class II alleles. For peptides presented by three or more alleles, truncation studies revealed that some contained multiple epitopes. These results contrast with the perceived notion that tetanus toxoid responses are dominated by universal CD4+ T-cell epitopes. Rather these results illustrate heterogeneous T-cell responses for different class II alleles and individual-specific variation of the T-cell repertoire.

Tumor necrosis factor alpha inhibits the suppressive effect of regulatory T cells on the hepatitis B virus-specific immune response

Chronicity of hepatitis B virus (HBV) infection is characterized by a weak immune response to the virus. CD4+CD25+ regulatory T cells (Treg) are present in increased numbers in the peripheral blood of chronic HBV patients, and these Treg are capable of suppressing the HBV-specific immune response. The aim of this study was to abrogate Treg-mediated suppression of the HBV-specific immune response. Therefore, Treg and a Treg-depleted cell fraction were isolated from peripheral blood of chronic HBV patients. Subsequently, the suppressive effect of Treg on the response to HBV core antigen (HBcAg) and tetanus toxin was compared, and the effect of exogenous tumor necrosis factor alpha (TNF-alpha), interleukin-1-beta (IL-1beta), or neutralizing antibodies against interleukin-10 (IL-10) or transforming growth factor beta (TGF-beta) on Treg-mediated suppression was determined. The results show that Treg of chronic HBV patients had a more potent suppressive effect on the response to HBcAg compared with the response to tetanus toxin. Neutralization of IL-10 and TGF-beta or exogenous IL-1beta had no effect on Treg-mediated suppression of the anti-HBcAg response, whereas exogenous TNF-alpha partially abrogated Treg-mediated suppression. Preincubation of Treg with TNF-alpha demonstrated that TNF-alpha had a direct effect on the Treg. No difference was observed in the type II TNF receptor expression by Treg from chronic HBV patients and healthy controls.

CONCLUSION

Treg-mediated suppression of the anti-HBV response can be reduced by exogenous TNF-alpha. Because chronic HBV patients are known to produce less TNF-alpha, these data implicate an important role for TNF-alpha in the impaired antiviral response in chronic HBV.

Low serum immunoglobulin G2 levels in infancy can be transient

OBJECTIVE

The immunoglobulin G2 subclasses contain predominantly antipolysaccharide antibodies. It was therefore believed intuitively that low immunoglobulin G2 levels could predispose individuals to infections with encapsulated bacteria. Although many reports initially supported this notion, more recent studies challenged it. Regardless of the biological significance, the natural history of low immunoglobulin G2 levels has not been carefully studied.

METHODS

We studied the outcome of low serum immunoglobulin G2 subclass levels in children. Thirteen patients who were referred because of recurrent infections were found to have low immunoglobulin G2 levels. Laboratory evaluation at presentation and follow-up visits included total serum immunoglobulins, immunoglobulin subclasses, and specific antibodies to protein antigens and to pneumococcal vaccine.

RESULTS

Low immunoglobulin G2 levels resolved completely within 0.6 years to 6 years (median: 1.5 years) in all patients. All 13 patients responded adequately to vaccination with protein antigens such as tetanus toxoid and polio as well as to immunization with pneumococcal vaccine. Four of 13 patients had a previous history of transient hypogammaglobulinemia, raising the possibility that the other cases may simply represent the tail end of this condition.

CONCLUSION

We have demonstrated that low immunoglobulin G2 detected in early infancy and childhood is likely to resolve completely within several months and up to 6 years from the time of presentation.

[Study of four kits used for titration of tetanus antibody for selection of plasma donors intended to fractionation]

Antitetanus antibodies titration is carried out by French National Blood Services (FNBSs) with the aim of seeking donors whose title of antibodies are greater or equal to 8 IU/ml. Different kits are used: ELISA antitetanus toxoid IgG (The Binding Site), ELISAT (Diagast), tetanus toxoid IgG ELISA (Diamed), ELISA IgG tetanus (Ingen). As the results obtained using these different reagents show some discrepancies with the control results carried out by the Laboratoire Français des Biotechnologies (LFB), it appeared necessary to harmonize the selection practices. With this intention a study of the different kits was initiated.

METHOD

Different samples were used during this evaluation: (1) the Reference Control (RC) used by the FNBS; (2) a serum sample of high title; (3) a range of dilution of national standard. The following tests were carried out: (1) robustness with the evaluation of the contamination and the board effect; (2) linearity and repeatability (eight deposits of each standard, RC and points of national standard dilutions); (3) reproducibility; (4) homogeneity. After automatic dilution of the samples, the plates were then processed according to the protocol of the manufacturer.

RESULTS

The study gives the CV in percentage of repeatability and reproducibility, the values of the standards provided as well as the bias compared to the RC and the uncertainty of measurements.

CONCLUSION

This study gave the possibility to rank each kit compared to RC and to specify the variations which surround each result. This variation can explain the discrepancy of conformity of plasma when title is close to the threshold of selection.

Failure to respond to hepatitis B vaccine in children with celiac disease

OBJECTIVES

To determine whether children with celiac disease (CD) fail to show a response to hepatitis B virus (HBV) vaccine more frequently than children without CD.

PATIENTS AND METHODS

This was a prospective study that compared the response to HBV, tetanus, rubella, and Haemophilus influenzae type b (Hib) vaccines between children with CD and age- and sex-matched control subjects.

RESULTS

The study population included 26 patients with CD and 18 age- and sex-matched controls. All had received the full complement of childhood vaccinations. A significantly higher proportion of subjects in the CD group (14 of 26) failed to respond to HBV vaccine compared with controls (2 of 18; 53.9% vs 11.1%; P < 0.05). Patients with CD were 8.33 times more likely to test negative for hepatitis B surface antigen than control subjects (95% CI, 1.5-46.5). By contrast, all of the subjects in both groups tested positive for rubella antibodies; only 1 subject in the CD group tested negative for tetanus antibody versus none in the control group (3.9% vs 0%; P = 1.0). The percentage of subjects who tested negative for Hib antibodies was similar in the 2 groups (CD, 33.3%; control, 44.4%; P = 0.53).

CONCLUSIONS

More than 50% of children with CD do not show a response to standard vaccination regimens for HBV. Given the large number of children with CD throughout the world, this observation suggests that there is a large HBV-susceptible population despite widespread vaccination. Current immunization strategies may need to be reassessed to protect this population and achieve the goal of universal protection.

C3b complexation diversifies naturally processed T cell epitopes

In addition to its well-established role in innate immunity, the complement component C3 is of critical importance in modulating the humoral response. In this study, we examined the effect of C3b linkage to tetanus toxin (TeNT) in the production of antigenic peptides inside human APC. We purified HLA-DR associated peptides isolated either from TeNT or TeNT-C3b pulsed cells. This study revealed that TeNT-C3b derived antigenic peptides are different and more numerous than TeNT derived peptides. This increased production of antigenic peptides correlated with a C3b-induced TeNT modification of proteolysis. These findings argue in favour of a new role for C3b in the modulation of T cell epitope during antigen processing and presentation.

Candidate live, attenuated Salmonella enterica serotype Typhimurium vaccines with reduced fecal shedding are immunogenic and effective oral vaccines

Environmental shedding of genetically manipulated microorganisms is an issue impeding the development of new live vaccines. We have investigated the immunogenicity of a number of novel Salmonella enterica serotype Typhimurium oral vaccine candidates that express the fragment C (TetC) component of tetanus toxin and harbor combinations of additional mutations in genes shdA, misL, and ratB that contribute to the persistence of serotype Typhimurium's colonization of the intestine. Serotype Typhimurium aroA (TetC) derivatives harboring additional mutations in either shdA or misL or combinations of these mutations exhibited a marked decrease in shedding of the vaccine strain in the feces of orally vaccinated mice. However, equivalent levels of anti-TetC and anti-Salmonella lipopolysaccharide immunoglobulin G (IgG), IgG1, IgG2a, and IgA were detected in sera of the vaccinated but not of the control mice. Cellular immune responses to TetC were detected in all vaccinated mice, regardless of the presence of the additional mutations in shdA or misL. Further, immunization with serotype Typhimurium aroA candidate vaccines harboring shdA and misL afforded complete protection against challenge with a virulent strain of serotype Typhimurium.

Germination-independent induction of cellular immune response by Bacillus subtilis spores displaying the C fragment of the tetanus toxin

Bacillus subtilis spores displaying the tetanus toxin fragment C (TTFC) on their surface have been previously shown to induce the production of specific IgG and secretory IgA in mice immunized through the oral or nasal route. Aim of this study was to analyze whether these spores were also able to induce cellular immunity, and whether such immune response was dependent on spore germination in the animal gastro-intestinal tract (GIT). We first developed a germination defective strain of B. subtilis unable to produce viable cells inside the mouse GIT. Germination-defective and congenic wild-type spores both expressing TTFC on their surface were then used to orally immunize Balb/C mice. Both types of spores induced spleen and mesenteric lymph nodes cell proliferation as well as production of IFNgamma but not of IL-4 and IL-10 in both districts. Our results indicate that recombinant spores preferentially induce a strong cell-mediated immune response with a Th1 phenotype, independently from their ability to germinate in the GIT.

Impact of plasmid stability on oral DNA delivery by Salmonella enterica serovar Typhimurium

Live attenuated Salmonellae may overcome limitations with conventional methods of DNA immunisation. This study examined the impact of plasmid stability on oral DNA delivery by the attenuated Salmonella enterica serovar Typhimurium vaccine strain BRD509. A DNA vaccine cassette comprising the C fragment of tetanus toxin under control of the cytomegalovirus (CMV) promoter was ligated into plasmid pcDNA3, pUC18, pBBR122, pACYC184, pRSF1010/CAT, pBR322 and pAT153. In vitro and in vivo stability studies revealed that, with the exception of pcDNA3 and pUC18, the plasmids were retained by BRD509. However, pAT153 was the only plasmid to induce a tetanus toxoid-specific antibody response following oral delivery. Plasmid copy number was found to impact on plasmid stability and the induction of antigen-specific humoral responses.

Prime-Boost with Alternating DNA Vaccines Designed to Engage Different Antigen Presentation Pathways Generates High Frequencies of Peptide-Specific CD8+ T Cells

The route for presentation of Ag to CD8+ or CD4+ T cells following DNA vaccination is critical for determining outcome, but the pathways involved are unclear. In this study, we compare two different DNA vaccine designs aimed to elicit CD8+ T cell responses against a specific peptide-epitope either by direct- or cross-presentation. Each carries sequences from tetanus toxin (TT) to provide essential CD4+ T cell help. In the first already proven design, the peptide-epitope is fused to the N-terminal domain of fragment C from TT. This appears to act mainly by cross-presentation. In the second design, the peptide-epitope is encoded by a minigene, with induction of Th responses mediated by coexpression of a hybrid invariant chain molecule, incorporating a single determinant from TT (p30) in exchange for class II-associated invariant chain peptide. This design appears to act mainly via direct presentation from transfected APCs. Both vaccines mediated Th-dependent priming of CD8+ T cells in mice, but the kinetics and level of the responses differed markedly, consistent with engagement of distinct pathways of Ag presentation. Importantly, the vaccines could be combined in an alternating prime-boost regime, in either order, generating substantially expanded memory CD8+ T cells, with potent effector function. Taken together, these results demonstrate that vaccination protocols involving different modes of Ag presentation at prime and boost can significantly improve the effectiveness of immunization.

Effect of month of vaccine administration on antibody responses in The Gambia and Pakistan

OBJECTIVE

To explore the relationship between calendar month of administration and antibody (Ab) response to vaccination in subjects from The Gambia and Pakistan, two countries with distinct patterns of seasonality.

METHODS

Three cohorts were investigated: Responses to rabies and pneumococcal vaccine were assessed in 472 children (mean age 8 years, males 53%) from rural Gambia. Responses to tetanus, diphtheria and hepatitis B (HBsAg) were investigated in 138 infants also from The Gambia (birth to 52 weeks of age, males 54%). Responses to rabies and Vi typhoid vaccines were assessed in 257 adults from Lahore, Pakistan (mean age 29.4 years, males 57%).

RESULTS

In Gambian children, significant associations were observed between month of vaccination and Ab response for the pneumococcal and rabies vaccines. As no consistent pattern by month was observed between the responses, it is assumed that different immunomodulatory stimuli or mechanisms were involved. In Pakistani adults, a significant pattern by month of vaccination was observed with both rabies and typhoid vaccine. No monthly influences were observed in the infant study to the tetanus, diphtheria or the HbsAg vaccines.

CONCLUSIONS

Antibody responses to certain specific vaccines are influenced by month of administration. Further research is required to elucidate the precise mechanisms explaining these observations, but a co-stimulatory effect of seasonally variable environmental antigens is a likely cause. Future studies of Ab response to vaccination in countries with a seasonally dependent environment should consider month of vaccination when interpreting study findings.

Reduction of the ganglioside binding activity of the tetanus toxin HC fragment destroys immunogenicity: implications for development of novel tetanus vaccines

In this study, the immunogenicities of the nontoxic H(C) fragment of tetanus toxin and derivatives lacking ganglioside binding activity were compared with that of tetanus toxoid after subcutaneous immunization of mice. Wild-type H(C) (H(C)WT) protein and tetanus toxoid both elicited strong antibody responses against toxoid and H(C) antigens and provided complete protection against toxin challenge. Mutants of H(C) containing deletions essential for ganglioside binding elicited lower responses than H(C)WT. H(C)M115, containing two amino acid substitutions within the ganglioside binding site, provided reduced protection against tetanus toxin challenge compared with H(C)WT, consistent with lower anti-H(C) and anti-toxoid antibody titers. Circular-dichroism spectroscopy and intrinsic fluorescence spectroscopy showed minimal structural perturbation in H(C)M115. We conclude that the presence of the ganglioside binding site within H(C) may be essential for induction of a fully protective anti-tetanus response comparable to that induced by tetanus toxoid by subcutaneous injection.

Expression of HLA-DP0401 molecules for identification of DP0401 restricted antigen specific T cells

Human histocompatibility leukocyte antigen (HLA)-DPA1*0103/DPB1*0401 (DP0401) is the most common HLA class II molecule and is present in approximately 45% of the Caucasian population. In this study, soluble HLA-DP0401 molecules were expressed as "empty'' class II molecules in insect cells. Utilizing these soluble DP molecules and the Tetramer Guided Epitope Mapping (TGEM) approach, the influenza A Puerto Rico/8/34 matrix protein (MP) derived peptide MP(41-60) VLMEWLKTRPILSPLTKGIL and the Clostridium tetani Tetanus Toxin (TT) derived peptide TT(634-653) DKISDVSTIVPYIGPALNIV were identified as the DP0401 restricted MP and TT epitopes, respectively. In addition, T cells specific for the cancer testis antigen NY-ESO-1 and the breast/ovarian cancer over-expressing antigen Her-2/neu were detected in DP0401 subjects by DP0401 tetramers. The availability of HLA-DP0401 tetramers should facilitate the study of DP restricted T cell responses.

Enhanced immunisation and expression strategies using bacterial spores as heat-stable vaccine delivery vehicles

Spores of the gram positive bacterium Bacillus subtilis have been used as oral vaccine vehicles and have been shown to confer protection against tetanus in mice. In this work, we have used tetanus as a model with which to examine different antigen presentation strategies as well as dosing regimes using the TTFC antigen of Clostridium tetani. We show that display of the antigen on the spore surface produces a more pronounced, but less rapid, response than when the antigen is expressed in the germinating spore; though this response has a clear Th1 bias. When using the nasal dosing route ten times less spores were needed to produce the same level of protective antibodies using surface display of TTFC. Expression of the antigen within the germinating spore by contrast enables as little as three oral doses on consecutive days to generate protection with a noticeable Th2 bias. We have also shown that TTFC can be expressed using two routes, using display on the spore surface as well as in the germinating spore. This dual route produced the best responses in terms of magnitude and speed of neutralising response as well as a clear Th1 bias indicating the involvement of cellular as well as humoral responses.

Expression and purification of a trivalent pertussis toxin-diphtheria toxin-tetanus toxin fusion protein in Escherichia coli

Pertussis toxoid, diphtheria toxoid, and tetanus toxoid are key components of diphtheria-tetanus-acellular pertussis vaccines. The efficacy of the vaccines is well documented, however, the vaccines are expensive partly because the antigens are derived from three different bacteria. In this study, a fusion protein (PDT) composed of the immunoprotective S1 fragment of pertussis toxin, the full-length non-toxic diphtheria toxin, and fragment C of tetanus toxin was constructed via genetic means. The correct fusion was verified by restriction endonuclease analysis and Western immunoblotting. Escherichia coli carrying the recombinant plasmid (pCoPDT) produced a 161kDa protein that was recognized by antibodies specific to the three toxins. The expression of the PDT protein was inducible by isopropyl-beta-d-thio-galactoside but the total amount of protein produced was relatively low. Attempts to improve the protein yield by expression in an E. coli strain (Rosetta-gami 2) that could alleviate rare-codon usage bias and by supplementation of the growth media with amino acids deemed to be a limiting factor in translation were not successful. The PDT protein remained in the insoluble fraction when the recombinant E. coli was grown at 37 degrees C but the protein became soluble when the bacteria were grown at 22 degrees C. The PDT protein was isolated via affinity chromatography on a NiCAM column. The protein was associated with five other proteins via disulfide bonds and non-covalent interactions. Following treatment with beta-mercaptoethanol, the PDT fusion was purified to homogeneity by preparative polyacrylamide gel electrophoresis with a yield of 45 microg/L of culture. Antisera generated against the purified PDT protein recognized the native toxins indicating that some, if not all, of the native epitopes were conserved.

DNA fusion vaccines induce epitope-specific cytotoxic CD8(+) T cells against human leukemia-associated minor histocompatibility antigens

The graft-versus-leukemia effect of allogeneic stem-cell transplantation is believed to be mediated by T-cell recognition of minor histocompatibility antigens on recipient cells. For minor histocompatibility antigens HA-1 and HA-2, normal cell expression is restricted to hemopoietic cells, and boosting the immune response to these antigens may potentiate graft-versus-leukemia effect without accompanying graft-versus-host disease. To increase efficacy, expansion of HA-1- or HA-2-specific CTL before transplantation is desirable. However, primary HA-1- or HA-2-specific CTL expanded in vitro are often of low avidity. An alternative approach is to prime specific CTL responses in vivo by vaccination. Clearly, donor vaccination must be safe and specific. We have developed DNA fusion vaccines able to induce high levels of epitope-specific CTL using linked CD4(+) T-cell help. The vaccines incorporate a domain of tetanus toxin (DOM) fused to a sequence encoding a candidate MHC class I binding peptide. This design generates antitumor CD8(+) T-cell responses and protective immunity in preclinical models. For clinical application, we constructed vaccines encoding HLA-A*0201-restricted peptides from human HA-1 and HA-2, which were fused to DOM, and tested their performance in HLA-A*0201-transgenic mice. Priming induced epitope-specific, IFNgamma-producing CD8(+) T cells with cytotoxic function boosted to high levels with electroporation. Strikingly, these mouse T cells efficiently killed human lymphoblastoid cell lines expressing endogenous HA-1 or HA-2. High avidity is indicated by the independence of cytolysis from CD8/MHC class I interaction. These safe epitope-specific vaccines offer a potential strategy to prime HA-1- or HA-2-specific CTL in transplant donors before adoptive transfer.

Immunization does not interfere with uptake and transport by motor neurons of the binding fragment of tetanus toxin

The nontoxic binding domain of tetanus toxin (fragment C or TTC) readily undergoes retrograde axonal transport from an intramuscular injection site. This property has led to investigation of TTC as a possible vector for delivering therapeutic proteins to motor neurons. However, the vast majority of individuals in the developed world have been vaccinated with tetanus toxoid and have circulating antitetanus antibodies that cross-react with TTC and may block the delivery of a TTC-linked therapeutic protein. However, it is uncertain whether the immune response is capable of completely neutralizing an intramuscular depot of protein prior to its internalization by presynaptic nerve terminals, where it is inaccessible to antibody. We have evaluated uptake of rhodamine-labeled TTC following intramuscular injection in normal animals and animals vaccinated with tetanus toxoid prior to injection of fluorescently labeled TTC. All animals demonstrated uptake of TTC, with fluorescence appropriately localized to the hypoglossal nerve and nucleus. The distribution and intensity of fluorescence within neurons and processes were indistinguishable between the two groups and were characteristic of TTC. Vaccinated animals showed levels of uptake of TTC into the brain comparable to those of immunologically naïve animals as measured by quantitative fluorimetry. All vaccinated animals had protective levels of antitetanus antibodies as measured by ELISA. Uptake of TTC by nerve terminals from an intramuscular depot is an avid and rapid process and is not blocked by vaccination associated with protection from tetanus toxin.

Mapping of the regions on the heavy chain of botulinum neurotoxin A (BoNT/A) recognized by antibodies of cervical dystonia patients with immunoresistance to BoNT/A

The purpose of this work was to map the entire recognition profile of the H chain of botulinum neurotoxin A (BoNT/A) by Abs in sera that have protective anti-BoNT/A Abs by the mouse protection assay (MPA) from cervical dystonia (CD) patients who had been treated with botulinum neurotoxin, serotype A (BOTOX). In previous studies we found that human anti-tetanus neurotoxin (TeNT) Abs cross-react with BoNT/A and BoNT/B. In the present work we devised an assay procedure for measuring specific anti-BoNT/A Abs in human sera by absorbing out or inhibiting the anti-TeNT Abs with TeNT before analyzing the sera for the anti-BoNT/A Abs. The sera were obtained from 28 CD patients who had become unresponsive to treatment with BoNT/A and the sera were found to protect mice against a lethal dose of BoNT/A. For localization of the Ab-binding regions on the H chain we employed a set of sixty, 19-residue synthetic peptides (except for peptide C31 which was 22 residues) that encompassed the entire H chain sequence 449-1296 and overlapped consecutively by five residues. The pattern of Ab recognition varied from patient to patient, but a very limited set of peptides were recognized by most of the patients. These were, in decreasing amounts of Ab binding, peptide N25 (H chain residues 785-803), C9/C10 (967-985/981-999), C31 (1275-1296), C15 (1051-1069), C20 (1121-1139), N16 (659-677), N22 (743-761), and N4 (491-509). But not every serum recognized all these peptides. The finding that the binding profile was not the same for all the patients is consistent with previous observations that immune responses to protein antigens are under genetic control and that the response to each epitope within a protein is under separate genetic control. Except for the region within C9/C10, the other regions either coincided (N16 and C31), or overlapped (N4, N22, N25, C15 and C20), with the recently mapped synaptosomes (snps)-binding regions on the H chain. The molecular and clinical implications of these findings are discussed.