Clinical Vaccine Studies Research Articles

CTLA-4 blockade during dendritic cell based booster vaccination influences dendritic cell survival and CTL expansion

Dendritic cells (DCs) are potent antigen-presenting cells and critical for the priming of CD8+ T cells. Therefore the use of these cells as adjuvant cells has been tested in a large number of experimental and clinical vaccination studies, in particular cancer vaccine studies. A number of protocols are emerging that combine vaccination with CTL expanding strategies, such as e.g. blockade of CTLA-4 signalling. On the other hand, the lifespan and in vivo survival of therapeutic DCs have only been addressed in a few studies, although this is of importance for the kinetics of CTL induction during vaccination. We have previously reported that DCs loaded with specific antigens are eliminated by antigen specific CTLs in vivo and that this elimination affects the potential for in vivo CTL generation. We now show that CTLA-4 blockade increases the number of DC vaccine induced LCMV gp33 specific CTLs and the lysis of relevant in vivo targets. However, the CTLA-4 blockage dependent expansion of CTLs also affect DC survival during booster DC injections and our data suggest that during a booster DC vaccine, the largest increase in CTL levels is already obtained during the first vaccination.

Immunisation with recombinant modified vaccinia virus Ankara expressing HIV‐1 gag in HIV‐1‐infected subjects stimulates broad functional CD4+ T cell responses

Virus-specific CD4+ T cells with IL-2-secreting and/or proliferative capacity are detected readily in HIV-1-infected long-term nonprogressors and rarely in persons with untreated progressive infection. The contribution of these cells to viraemia control is uncertain, but this question might be addressed in clinical therapeutic vaccination studies. However, the quality of T helper responses induced by currently available HIV-1 vaccine candidates has not been explored in depth. We determined the effect of vaccination with modified vaccinia virus Ankara (MVA) expressing HIV-1 gag p24/p17 (MVA.HIVA) on HIV-1-specific CD4+ T cell responses in 16 chronically infected, highly active antiretroviral therapy (HAART)-treated subjects using CD8-depleted IFN-gamma ELISPOT assays, intracellular cytokine staining assays for IL-2 and IFN-gamma, and a CFSE-based proliferation assay. Gag-specific CD4+ T cell responses were significantly increased in magnitude and breadth after vaccination and targeted both known and new epitopes, several of which were also recognised by healthy HIV-uninfected volunteers immunised with the same vaccines. The frequencies of CD4+ T cells expressing IL-2 or IFN-gamma, alone or simultaneously, were also augmented. These findings indicate that functional virus-specific T helper cells can be boosted by vaccination in chronic HIV-1 infection. Further evaluation of their role in viraemia control is warranted.

Clinical studies of experimental vaccines

The scope of this review is to provide the current status of HIV vaccine clinical development. A series of issues regarding the type of immune response stimulated by the candidate vaccines in the pipeline, the advances in the immune correlates of protection, the need for an effective decision-making process for selection of candidate vaccines into further clinical development and the rationale for clinical trials will also be discussed. Efforts in the development of HIV vaccines inducing broad neutralizing antibodies have failed so far. The current pipeline is predominantly composed of candidate vaccines designed to induce cellular immunity and particularly T-cell response. For these reasons, these candidate vaccines have been termed 'T-cell vaccines'. A large number of candidate vaccines or vaccine combinations have entered phase I-II clinical trials in 2005. Furthermore, an adenovirus vector-based vaccine has entered proof-of-concept efficacy trial and a canarypox vector in combination with a protein-based vaccine is currently being evaluated in phase III clinical trials. T-cell vaccines have been shown to be safe and the most recent generation of these vaccines also has substantial immunogenicity. Only clinical trials can provide the definitive answer to immune correlates of protection and vaccine efficacy.

Vaccination for Leukemia

Myeloid forms of leukemia would seem to be an ideal disease for investigators wishing to develop targeted immunotherapy because the leukemia is derived from antigen-presenting cells and because clinical data have demonstrated that there is potent T-cell immunity to chronic myeloid leukemia when donor lymphocyte infusions are used to treat relapse after transplantation. However, clinical vaccine studies have had to wait for the identification of specific antigens, some of which have recently been identified, and for a more complete understanding of basic tumor immunology. Here we review relevant fundamental T-cell biology, the nature of some important leukemia-associated antigens, and the preliminary results from recent clinical vaccine trials for leukemia. Although these studies are still early, they offer evidence that effective immunity to leukemia is possible after vaccination, thus setting the stage for future combined therapies.

Recommendations for the design and use of standard virus panels to assess neutralizing antibody responses elicited by candidate human immunodeficiency virus type 1 vaccines.

Laboratory measures of antigen-specific immunity are an essential component of the vaccine discovery process. For human immunodeficiency virus type 1 (HIV-1), this process will likely require iterative evaluations of vaccine immunogens to choose the most promising vaccine candidates to advance into human trials. To optimally evaluate and compare vaccine immunogens, we will need high-throughput assays that allow accurate and reproducible measurements of immune responses. In addition, vaccine sponsors and regulatory agencies appropriately require that immune assays associated with human trials be performed in laboratories that comply with guidelines for good laboratory practices (GLP). The rigorous process of assay validation associated with GLP can improve the accuracy of immune assessment assays and contribute to vaccine development by advancing our ability to distinguish incremental improvements in immune responses elicited by novel immunogens. In this commentary, we address several of these issues with regard to the measurement of anti-HIV-1 neutralizing antibodies (NAbs). We recommend the use of DNA plasmids encoding full-length functional HIV-1 envelope glycoproteins (Env); these env clones, when transfected with an HIV-1 envdefective molecular clone, produce well-characterized HIV-1 Env pseudovirions. Additionally, we recommend the establishment of standardized panels of Env-pseudotyped viruses to assess the potencies and breadths of NAbs elicited by vaccine immunogens. These virus panels would form the basis for GLP neutralization assays used to assess sera from clinical vaccine studies, and the same virus panels could be used by investigators interested in the preclinical evaluation of vaccine immunogens.

Studies of equivalence in clinical vaccine research

The development of combination vaccines as well as the improved manufacture of vaccines have resulted in the need for clinical studies seeking equivalence or non-inferiority as investigators seek to demonstrate that combination vaccines achieve the same levels of efficacy, immunogenicity, and safety as their individual counterparts. Given the nature of the statistical analysis, studies of equivalence require particular attention to sample size. The current double-significance method of Neyman–Pearson attempts to address problems with equivalence testing, but it leads to very large sample sizes and illogical results. With such large samples, one can find a clinically trivial difference that is still statistically significant. The late Professor Alvan R. Feinstein proposed a more logical approach that would call for smaller, more workable sample sizes. Understanding the issues involved in sample size calculations for such studies is important to those who design clinical vaccine studies. The implications of the calculations will have far-reaching effects on the feasibility of the study such as availability of subjects, the success with recruitment, and the overall expenses. In fact, the feasibility issues may prevent the study being undertaken at all.

Sample sizes and negative studies in clinical vaccine research

Negative studies of vaccine adverse events occur with some frequency in the published literature. They serve important roles in fending off claims posed by the anti-vaccine movement and in reinforcing public health efforts to prevent diseases. Still, negative studies frequently suffer from concerns of adequate sample size. The double-significance Neyman–Pearson formula for sample size calculation that is now in vogue results in immense sample sizes that can lead to illogical interpretations. The late Professor Alvan R. Feinstein, the father of quantitative clinical epidemiology, proposed a more logical approach that would reduce the confusion and call for more moderate sample sizes. Understanding the issues involved in sample size calculations is important to those who design clinical vaccine studies. The implications of the calculations have far-reaching effects upon elements of feasibility such as the expense of the study, the ability to recruit adequate numbers, and even whether the study will be done at all.

Asymptotical Tests on the Equivalence, Substantial Difference and Non‐inferiority Problems with Two Proportions

AbstractLet d = p2 − p1 be the difference between two binomial proportions obtained from two independent trials. For parameter d, three pairs of hypothesis may be of interest: H1: d ≤ δ vs. K1: d > δ; H2: d ∉ (δ1, δ2) vs. K2: d ∈ (δ1, δ2); and H3: d ∈ [δ1, δ2] vs. K3: d ∉ [δ1, δ2], where Hi is the null hypothesis and Ki is the alternative hypothesis. These tests are useful in clinical trials, pharmacological and vaccine studies and in statistics generally. The three problems may be investigated by exact unconditional tests when the sample sizes are moderate. Otherwise, one should use approximate (or asymptotical) tests generally based on a Z‐statistics like those suggested in the paper. The article defines a new procedure for testing H2 or H3, demonstrates that this is more powerful than tests based on confidence intervals (the classic TOST – two one sided tests – test), defines two corrections for continuity which reduce the liberality of the three tests, and selects the one that behaves better. The programs for executing the unconditional exact and asymptotic tests described in the paper can be loaded at http://www.ugr.es/~bioest/software.htm. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Ex vivo analysis of human antigen-specific CD8+ T-cell responses: quality assessment of fluorescent HLA-A2 multimer and interferon-gamma ELISPOT assays for patient immune monitoring.

The authors developed a standardized approach for immune monitoring of antigen-specific CD8+ T cells within peripheral blood lymphocytes (PBLs) that combines direct ex vivo analysis of Melan-A/MART-1 and influenza-specific CD8+ T cells with HLA-A2/peptide multimers and interferon-gamma ELISPOT assays. Here the authors assessed the quality of results obtained with 180 PBLs from healthy donors and melanoma patients. Reproducibility of the multimer assay was good (average of 15% variation). In the absence of in vivo antigen-specific T-cell responses, physiologic fluctuations of multimer-positive T cells was low, with variation coefficients of 20% for Melan-A and 28% for influenza-specific T cells. In contrast, patients with vaccination-induced T-cell responses had significantly increased T-cell frequencies clearly exceeding physiologic fluctuations. Comparable results were obtained with ELISPOT assays. In conclusion, this approach is well suited to assess T-cell responses as biologic endpoints in clinical vaccine studies.

In vitro studies with recombinant Plasmodium falciparum apical membrane antigen 1 (AMA1): production and activity of an AMA1 vaccine and generation of a multiallelic response.

Apical membrane antigen 1 (AMA1) is regarded as a leading malaria blood-stage vaccine candidate. While the overall structure of AMA1 is conserved in Plasmodium spp., numerous AMA1 allelic variants of P. falciparum have been described. The effect of AMA1 allelic diversity on the ability of a recombinant AMA1 vaccine to protect against human infection by different P. falciparum strains is unknown. We characterize two allelic forms of AMA1 that were both produced in Pichia pastoris at a sufficient economy of scale to be usable for clinical vaccine studies. Both proteins were used to immunize rabbits, singly and in combination, in order to evaluate their immunogenicity and the ability of elicited antibodies to block the growth of different P. falciparum clones. Both antigens, when used alone, elicited high homologous anti-AMA1 titers, with reduced strain cross-reactivity. Similarly, sera from rabbits immunized with a single antigen were capable of blocking the growth of homologous parasite strains at levels theoretically sufficient to clear parasite infections. However, heterologous inhibition was significantly reduced, providing experimental evidence that AMA1 allelic diversity is a result of immune pressure. Encouragingly, rabbits immunized with a combination of both antigens exhibited titers and levels of parasite inhibition as good as those of the single-antigen-immunized rabbits for each of the homologous parasite lines, and consequently exhibited a broadening of allelic diversity coverage.

Identification of tumour-associated T-cell epitopes for vaccine development.

Ten years ago, the first melanoma patient was successfully treated by vaccination with a short peptide, which was, in fact, the first tumour-specific T-cell epitope ever defined — MAGE. Since then, a number of clinical vaccination studies have underlined the potential of tumour-specific T-cell epitopes. But, how can we identify more epitopes to improve their efficacy as an anticancer treatment?

Vaccines in breast cancer

<h2>SUMMARY</h2> Several antigens recognized by cellular and humoral effectors of the immune system have been identified in breast cancer. ‘Cancer/Testis' antigens, e.g. MAGE, NY-ESO-1, CT-7; differentiation antigens, e.g. NY-BR-1, CEA; overexpressed antigens, e.g. p53, HER2/neu, MUC-1, LewisX; and mutational antigens, e.g. p53, represent potential targets for antigen-specific immunotherapy. Clinical vaccine studies, mostly performed in melanoma, and aimed at the induction of antigen-specific CD8+ T cell responses in vivo, have helped to establish sensitive tools for the monitoring of immune responses to the vaccine in vivo and in vitro. Delayed-type hypersensitivity (DTH) reactions observed after intradermal injection of antigenic peptides were found to closely correlate with the induction of antigen-specific CD8+ T cell responses. Cytokines (GM-CSF, IL-2, IL-12) and adjuvants (QS21, IFA, MHC class II restricted helper peptides) have mediated increased CD8+ T cell responses against different antigenic peptides. The site of immunization may have important implications for the quality of immune responses induced. Intradermal and intralymphatic vaccination has led to strong CD8+ T cell responses in vivo, measurable at the immunization site, in metastatic lesions and in the peripheral blood. Intravenous and subcutaneous vaccination have induced measurable immune responses less frequently. Different strategies of vaccination using dendritic cells loaded with antigenic peptides, proteins or lysates prepared from autologous or allogeneic tumour cells have also led to measurable immune responses in vivo. Results, however, were not superior to vaccination with antigenic peptides alone or combined with adjuvants. Focusing on breast cancer, one of the most promising antigens for the design of vaccine studies is the CT-antigen NY-ESO-1, which was identified by the SEREX method. NY-ESO-1 is expressed in approximately 30–50% of breast cancers. Spontaneous humoral and cellular immune responses against NY-ESO-1 can be detected in 50% of patients with NY-ESO-1+ tumours. Specific DTH- and CD8+ T cell responses were induced after vaccination with NY-ESO-1 derived peptides alone and combined with GM-CSF in the majority of NY-ESO-1-naive patients. Measurable immune responses that can be correlated with the clinical outcome represent an important prerequisite for any immunotherapeutic intervention in cancer immunotherapy. At present, measurable but limited disease will teach us about any immediate effects of immunotherapy on cancer cells. This will lead the way in the near future to sound and justified adjuvant treatment strategies in the specific immunotherapy of breast cancer.

Clinical studies of human papilloma vaccines in pre-invasive and invasive cancer

Cervical cancer is the second most common cause of cancer death in women worldwide. It is almost invariably associated with infection with human papilloma virus (HPV) particularly types 16 and 18. The ubiquitous expression of E6 and E7 oncogene products has been recognised as an attractive target for CTL-mediated immunotherapy. In-vivo expansion of an HPV oncogene product specific MHC class 1 restricted response has been demonstrated using intradermally administered live vaccinia virus HPV 16 and 18 E6/E7 gene construct (TA-HPV, Cantab Pharmaceuticals). Responses have been seen in 1/3 evaluable patients with advanced cervical cancer, and 3/12 CIN3 volunteers, and in 4/29 patients with early invasive cervical cancer (Rankin et al. Proceedings of 91st AACR Meeting, San Francisco, April 2000). In addition, the adoptive transfer of ex vivo HPV 16 or 18 positive autologous tumour lysate pulsed dendritic cells is currently being tested as an alternative means of expanding HPV specific CTL in advanced cervical cancer patients. So far an HLA-A*O201 restricted CD8 T cell response has been recorded in the single HLA-A*O201 patient whose tumour was shown to be HPV16 positive. It appears therefore feasible to induce HPV specific CTL responses in patients with cervical cancer using several vaccine strategies. However, further clinical trials are needed to determine the full anti-tumour potential of this vaccine based immunotherapy.

Dendritic Cells for Specific Cancer Immunotherapy

The characterization of tumor-associated antigens recognized by human T lymphocytes in a major histocompatibility complex (MHC)-restricted fashion has opened new possibilities for immunotherapeutic approaches to the treatment of human cancers. Dendritic cells (DC) are professional antigen presenting cells that are well suited to activate T cells toward various antigens, such as tumor-associated antigens, due to their potent costimulatory activity. The availability of large numbers of DC, generated either from hematopoietic progenitor cells or monocytes in vitro or isolated from peripheral blood, has profoundly changed pre-clinical research as well as the clinical evaluation of these cells. Accordingly, appropriately pulsed or transfected DC may be used for vaccination in the field of infectious diseases or tumor immunotherapy to induce antigen-specific T cell responses. These observations led to pilot clinical trials of DC vaccination for patients with cancer in order to investigate the feasibility, safety, as well as the immunologic and clinical effects of this approach. Initial clinical studies of human DC vaccines are generating encouraging preliminary results demonstrating induction of tumor-specific immune responses and tumor regression. Nevertheless, much work is still needed to address several variables that are critical for optimizing this approach and to determine the role of DC-based vaccines in tumor immunotherapy.

Clinical studies of human papilloma vaccines in cervical cancer.

Cervical cancer is the second most common cause of cancer death world wide’ and is a particular problem in developing countries. Even with optimum treatment approximately 40% continue to die from this disease.2There is therefore a need for new strategies to reduce global mortality, including immunotherapeutic intervention.

Genetically modified anthrax lethal toxin safely delivers whole HIV protein antigens into the cytosol to induce T cell immunity.

Bacillus anthrax lethal toxin can be engineered to deliver foreign proteins to the cytosol for antigen presentation to CD8 T cells. Vaccination with modified toxins carrying 8-9 amino acid peptide epitopes induces protective immunity in mice. To evaluate whether large protein antigens can be used with this system, recombinant constructs encoding several HIV antigens up to 500 amino acids were produced. These candidate HIV vaccines are safe in animals and induce CD8 T cells in mice. Constructs encoding gag p24 and nef stimulate gag-specific CD4 proliferation and a secondary cytotoxic T lymphocyte response in HIV-infected donor peripheral blood mononuclear cells in vitro. These results lay the foundation for future clinical vaccine studies.

Clinical immunogenicity and tolerance studies of liquid vaccines delivered by jet-injector and a new single-use cartridge (Imule ®): comparison with standard syringe injection

A new needleless jet-injector, Mini-Imojet ®, was developed that administers liquid vaccines from a single-use, pre-filled cartrige named Imule ®, which avoids the risk of cross-contamination. We conducted clinical trials in several settings in France and West Africa to compare the immunogenicity and tolerance of five vaccines (influenza vaccine, Vi capsular polysaccharide typhoid vaccine, tetanus toxoid vaccine, diphtheria-tetanus-whole cell pertussis vaccine, and inactivated hepatitis A vaccine) administered with the Imule ® system vs standard syringe technique. In each vaccine study, all subjects of either group were tested for serum antibody titres to calculate the geometrical mean titres and seroconversion rates after complete vaccination. Immediate local reactions were noted after each injection, and local and general reactions were evaluated during a predetermined period of follow-up. When delivered by the Imule ® technique, all the administered vaccines were of equivalent or superior immunogenicity, compared to the syringe technique. The tolerance to vaccines injected by the Imule ® system was acceptable in all studies. The most frequently observed reactions were mild (e.g. minor bleeding, superficial papules, erythema and induration) and could be considered to be inherent to the injection technique. The technical and safety advantages of the Mini-Imojet ®/Imule ® system, compared to sterilizable, standard disposable or autodestruct syringes and to classical multi-dose vial jet-injectors, reinforces the interest of this new injection technique for collective immunizations.

Augmenting the immunogenicity of carbohydrate tumor antigens

Antibody responses have identified cell surface carbohydrate antigens as potentially immunogenic cancer antigens in a variety of different tumors, but immunization with whole tumor cells or cell lysates has only occasionally induced immune responses against these antigens. Three approaches to further augmenting their immunogenicity have been explored, mixture with immunological adjuvants, synthesis of more immunogenic derivatives and conjugation to immunogenic proteins. Conjugation to proteins such as KLH plus the use of potent adjuvants such as QS-21 proved most immunogenic. Carbohydrate epitopes on gangliosides (GM2 and GD2), neutral glycolipids (Le v and Globo H) and glycoproteins (Le v, Globo H, TF, sTn and Tn) are of special interest. Each of these antigen has been synthesized and conjugated to KLH. Their use in preclinical or clinical vaccination studies has resulted in increased IgM and IgG antibody responses against tumors expressing these antigens. Phase I–II clinical trials in patients with cancer have been initiated with each to optimize immunogenicity. The GM2 vaccine has progressed to Phase III trials and the sTn vaccine to Phase II trials aimed at determining the impact of vaccination on survival.

O-Specific Side-Chain Toxin-Protein Conjugates as Parenteral Vaccines for the Prevention of Shigellosis and Related Diseases

Only indirect evidence has been cited to document that lipopolysaccharide-mediated virulence at the bacterial level and serum antibodies to the O-specific side chain of the lipopolysaccharide molecule may prevent shigellosis. Our proposed use of the B subunit of Shiga toxin as a carrier protein is based upon evidence (even more indirect) that serum antitoxin may reduce the severity of dysentery and diarrhea. Because animal models of disease may provide information inapplicable to the prediction of vaccine-induced protective immunity, we suggest that clinical trials in the population at risk should be started after successful completion of the safety and immunogenicity phases of vaccine development in laboratory animals and in the target population. Clinical studies of shigella vaccines are difficult because of the many causes of dysentery in a population with a high rate of intestinal disease.

Clinical Studies of Influenza Vaccines--1978

Clinical Studies of Influenza Vaccines—1978 Get access Reviews of Infectious Diseases, Volume 5, Issue 4, July 1983, Page 721, https://doi.org/10.1093/clinids/5.4.721 Published: 01 July 1983