The use of Flt3 ligand as an adjuvant for hepatitis B vaccination of healthy adults

Influence of Granulocyte-Macrophage Colony-Stimulating Factor or Influenza Vaccination on HLA-DR, Infection and Delirium Days in Immunosuppressed Surgical Patients: Double Blind, Randomised Controlled Trial

PURPOSE

Surgical patients are at high risk for developing infectious complications and postoperative delirium. Prolonged infections and delirium result in worse outcome. Granulocyte-macrophage colony-stimulating factor (GM-CSF) and influenza vaccination are known to increase HLA-DR on monocytes and improve immune reactivity. This study aimed to investigate whether GM-CSF or vaccination reverses monocyte deactivation. Secondary aims were whether it decreases infection and delirium days after esophageal or pancreatic resection over time.

METHODS

In this prospective, randomized, placebo-controlled, double-blind, double dummy trial setting on an interdisciplinary ICU of a university hospital 61 patients with immunosuppression (monocytic HLA-DR [mHLA-DR] <10,000 monoclonal antibodies [mAb] per cell) on the first day after esophageal or pancreatic resection were treated with either GM-CSF (250 μg/m2/d), influenza vaccination (Mutagrip 0.5 ml/d) or placebo for a maximum of 3 consecutive days if mHLA-DR remained below 10,000 mAb per cell. HLA-DR on monocytes was measured daily until day 5 after surgery. Infections and delirium were followed up for 9 days after surgery. Primary outcome was HLA-DR on monocytes, and secondary outcomes were duration of infection and delirium.

RESULTS

mHLA-DR was significantly increased compared to placebo (p < 0.001) and influenza vaccination (p < 0.001) on the second postoperative day. Compared with placebo, GM-CSF-treated patients revealed shorter duration of infection (p < 0.001); the duration of delirium was increased after vaccination (p = 0.003).

CONCLUSION

Treatment with GM-CSF in patients with postoperative immune suppression was safe and effective in restoring monocytic immune competence. Furthermore, therapy with GM-CSF reduced duration of infection in immune compromised patients. However, influenza vaccination increased duration of delirium after major surgery.

TRIAL REGISTRATION

www.controlled-trials.com ISRCTN27114642.

Advances and challenges in mucosal adjuvant technology

Adjuvants play attractive roles in enhancement of immune response during vaccination; however, due to several challenges, only a limited number of adjuvants are licensed by health authorities. The lack of an effective mucosal adjuvant is even more significant as none of the licensed adjuvants revealed a strong enhancement in immune system after mucosal administration. Over the past two decades, several mucosal adjuvants have been developed to deliver antigens to the target cells in the mucosal immune system and increase specific immune responses. However, the safety and efficacy of these adjuvants for testing in human trials is still an important issue, requiring further study. In this article, we briefly review the challenges associated with most common mucosal adjuvants and discuss potential strategies for targeting the mucosal immune system.

Clearance of persistent HPV infection and cervical lesion by therapeutic DNA vaccine in CIN3 patients

Here, we demonstrate that electroporation-enhanced immunization with a rationally designed HPV DNA vaccine (GX-188E), preferentially targeting HPV antigens to dendritic cells, elicits a significant E6/E7-specific IFN-γ-producing T-cell response in all nine cervical intraepithelial neoplasia 3 (CIN3) patients. Importantly, eight out of nine patients exhibit an enhanced polyfunctional HPV-specific CD8 T-cell response as shown by an increase in cytolytic activity, proliferative capacity and secretion of effector molecules. Notably, seven out of nine patients display complete regression of their lesions and viral clearance within 36 weeks of follow up. GX-188E administration does not elicit serious vaccine-associated adverse events at all administered doses. These findings indicate that the magnitude of systemic polyfunctional CD8 T-cell response is the main contributing factor for histological, cytological and virological responses, providing valuable insights into the design of therapeutic vaccines for effectively treating persistent infections and cancers in humans.

Improving vaccines by incorporating immunological coadjuvants

While vaccination continues to be the most successful interventionist health policy to date, infectious disease remains a significant cause of death worldwide. A primary reason that vaccination is not able to generate effective immunity is a lack of appropriate adjuvants capable of initiating the desired immune response. Adjuvant combinations can potentially overcome this problem; however, the possible permutations to consider, which include the route and kinetics of vaccination, as well as combinations of adjuvants, are practically limitless. This review aims to summarize the current understanding of adjuvants and related immunological processes and how this knowledge can and has been applied to the strategic selection of adjuvant combinations as components of vaccines against human infectious disease.

Towards tailored vaccine delivery: needs, challenges and perspectives

The ideal vaccine is a simple and stable formulation which can be conveniently administered and provides life-long immunity against a given pathogen. The development of such a vaccine, which should trigger broad and strong B-cell and T-cell responses against antigens of the pathogen in question, is highly dependent on tailored vaccine delivery approaches. This review addresses vaccine delivery in its broadest scope. We discuss the needs and challenges in the area of vaccine delivery, including restrictions posed by specific target populations, potentials of dedicated stable formulations and devices, and the use of adjuvants. Moreover, we address the current status and perspectives of vaccine delivery via several routes of administration, including non- or minimally invasive routes. Finally we suggest possible directions for future vaccine delivery research and development.

Evaluation of the effects of human leukocyte IFN-alpha on the immune response to the HBV vaccine in healthy unvaccinated individuals

HBV vaccine needs 3 injections over 6 months to induce immunity. Thus, the use of adjuvants capable of inducing earlier immune protection would be highly desirable. Most adjuvants may act by inducing cytokines, and among them, type I interferons (IFNs), deserve a special attention in view of the potent immunomostimulatory activity observed in mouse models and on dendritic cell functions. The aim of the present trial was to evaluate the effects of IFN-alpha administered as an adjuvant of HBV vaccine in healthy unvaccinated individuals. No significant enhancing effect on the antibody response was observed, in spite of an early and transient upregulation of costimulatory molecule expression on peripheral blood mononuclear cells, which may be suggestive of an IFN-mediated activation of antigen presenting cells. We conclude that, under the conditions used in this trial, natural IFN-alpha does not act as an adjuvant of the HBV vaccine in healthy unvaccinated individuals.

Spleen but not tumor infiltration by dendritic and T cells is increased by intravenous adenovirus-Flt3 ligand injection

Dendritic cell (DC) expansion is regulated by the hematopoietic growth factor fms-like tyrosine kinase 3 ligand (Flt3L). DCs are critical to the control of tumor growth and metastasis, and there is a positive correlation between intratumoral DC infiltration and clinical outcome. In this report, we first demonstrate that single intravenous (i.v.) injections of adenovirus (Adv)-Flt3L significantly increased splenic dendritic, B, T and natural killer (NK) cell numbers in both normal and mammary tumor-bearing mice. In contrast, the numbers of DCs and T cells infiltrating the tumors were not increased. Consistent with the minimal effect on immune cell infiltration, i.v. Adv-Flt3L injections had no therapeutic activity against orthotopic mammary tumors. In addition, we noted tumor and Adv-Flt3L expansion of Gr1(+)CD11b(+) immature myeloid suppressor cells (IMSCs), which may inhibit the therapeutic efficacy of Adv-Flt3L-expanded DCs.

Progress in drug development of immunostimulatory CpG oligodeoxynucleotide ligands for TLR9

Oligodeoxynucleotides (ODNs) with unmethylated deoxycytosine-deoxyguanosine (CpG) motifs are recognised by Toll-like receptor (TLR)9 expressed in specialised cell subsets of the human immune system, B cells and plasmacytoid dendritic cells. TLR9-mediated stimulation of the immune system leads to a plethora of directed effects linking innate to adaptive immune responses. This allows the use of TLR9 agonists as highly effective targeted immunomodulatory drugs with broad potential applications as vaccine adjuvants, stand-alone therapy or in combination with other therapies in cancer, infectious diseases or asthma and allergy. TLR9 agonists represent a new class of small (8-30 bases long), easily synthesised, non-antisense ODN pharmaceuticals.

PyNTTTTGT prototype oligonucleotide IMT504 is a potent adjuvant for the recombinant hepatitis B vaccine that enhances the Th1 response

PyNTTTTGT oligodeoxinucleotides (ODNs) cause activation, proliferation and immunoglobulin secretion on B cells, and the expression of co-stimulatory molecules on plasmacytoid dendritic cells of primates. It has now been discovered that these ODNs are also active on rat cells. This fact allowed us to investigate the adjuvant properties of PyNTTTTGT ODNs in a human Hepatitis B vaccine using this animal model. A very significant increment, as compared with the antigen alone, was observed in the antibody production induced by vaccination with the recombinant Hepatitis B surface antigen adjuvated with the PyNTTTTGT prototype IMT504 ODN. Analysis of the IgG subclass distribution in the sera of vaccinated animals indicated that, although an increase was observed in the titer of all the IgG subclasses, the increase on the Th1-associated IgG2b subclass was clearly more pronounced. Remarkably, this effect on the IgG2b titer was observed even if alum, a Th2 promoting adjuvant, was present together with IMT504 in the vaccine formulation. The increase in the Th1 response induced by IMT504 was also suggested by in vitro gamma interferon secretion assays. Monkeys of the species Cebus apella immunized with the recombinant Hepatitis B surface antigen plus alum and IMT504 also showed titers of antibodies against the antigen several times superior to the titers observed in control animals immunized with the antigen plus alum without ODN. Since rat and monkey cells are significantly less immunostimulated "in vitro" by PyNTTTTGT ODNs than human cells, the present results reasonably predict a very good performance of these ODNs as adjuvants in human vaccination.

CPG 7909, an immunostimulatory TLR9 agonist oligodeoxynucleotide, as adjuvant to Engerix-B HBV vaccine in healthy adults: a double-blind phase I/II study

Oligodeoxynucleotides containing immunostimulatory CpG motifs (CpG ODN) act as potent Th1-like immune enhancers with many antigens in animal models. We have extended these observations to the first clinical evaluation of the safety, tolerability and immunogenicity of CPG 7909 when added to a commercial HBV vaccine. In a randomized, double-blind phase I dose escalation study, healthy volunteers aged 18-35 years were vaccinated at 0, 4 and 24 weeks by intramuscular injection with Engerix-B (GlaxoSmithKline). The regular adult dose of 20 microg recombinant hepatitis B surface antigen (HBsAg) adsorbed to alum was administered mixed with saline (control) or with CPG 7909 at one of three doses (0.125, 0.5 or 1.0 mg). HBsAg-specific antibody responses (anti-HBs) appeared significantly sooner and were significantly higher at all timepoints up to and including 24 weeks in CPG 7909 recipients compared to control subjects (p< or = 0.001). Strikingly, most CpG 7909-vaccinated subjects developed protective levels of anti-HBs IgG within just two weeks of the priming vaccine dose. A trend towards higher rates of positive cytotoxic T cell lymphocyte responses was noted in the two higher dose groups of CPG 7909 compared to controls. The most frequently reported adverse events were injection site reactions, flu-like symptoms and headache. While these were more frequent in CPG 7909 groups than in the control group (p<0.0001), most were reported to be of mild to moderate intensity regardless of group. In summary, CPG 7909 as an adjuvant to Engerix-B was well-tolerated and enhanced vaccine immunogenicity. CPG 7909 may allow the development of a two-dose prophylactic HBV vaccine.

Murine mammary adenocarcinoma cells transfected with p53 and/or Flt3L induce antitumor immune responses

Transfection of tumors with tumor-associated antigens (Ags) or cytokines can increase immunogenicity and slow down tumor growth. However, the effect of cotransfection with genes that encode a tumor-associated Ag, such as the tumor suppressor gene p53, and a cytokine has been rarely investigated. We report that transfection of 4T1 mammary tumor cells (p53-null) with the dendritic cell (DC) growth factor, fms-like tyrosine kinase 3 ligand (Flt3L), significantly delayed their growth in vivo, resulting in the rejection of 100% of the tumors formed by injection of tumor cells cotransfected with Flt3L and p53. Immunization with irradiated 4T1 cells transfected with Flt3L induced DC infiltration of the immunization site and significantly increased the antitumor T-cell responses. Further, immunization with irradiated 4T1 cells cotransfected with p53 and Flt3L significantly increased p53-specific immune responses, as compared to vaccination with 4T1 cells transfected with either Flt3L or p53 alone. These responses included increased activity against clone 66 (Cl-66), a sister tumor to 4T1 with high murine mutant p53 expression levels. Challenge with Cl-66 revealed that immunization with irradiated 4T1-Flt3L-p53 cells significantly slowed growth, prolonged survival, and resulted in complete remissions. Further, immunization with irradiated 4T1-Flt3L also slowed Cl-66 growth, although to a lesser extent than 4T1-Flt3L-p53. We suggest that immunization with DCs transfected with the Flt3L transgene and a tumor Ag may potentially heighten T-cell responses and therapeutic activity.

Flt-3 ligand as adjuvant for DNA vaccination augments immune responses but does not skew TH1/TH2 polarization

Since transfection of dendritic cells (DC) plays a key role in DNA vaccination, in vivo expansion of DC might be a tool to increase vaccine efficacy. We asked whether Fms-like tyrosine kinase-3 ligand (Flt-3L), a growth factor for DC, can be used as an adjuvant for DNA vaccination. Beta-galactosidase (beta-gal) was used as a model antigen in C57BL/6 mice. Mice were immunized i.m. with DNA coding for beta-gal with or without additional injection of Flt-3L. In both cases, antigen-specific CD4+ and CD8+ T cells were detectable after vaccination. Compared with DNA alone, additional administration of Flt-3L led to a significant increase in the antigen-specific proliferative response. However, increased cytotoxicity by T cells was not observed. The cytokines secreted by splenocytes of immunized mice upon in vitro stimulation with antigen had a TH2 profile. Humoral responses against beta-gal preferentially consisted of IgG1 antibodies. Analysis of DC from Flt-3L-treated mice revealed an immature phenotype with low or absent expression levels of CD80, CD86 and CD40. We conclude that Flt-3L does not generally skew immune responses towards a TH1 type. More likely, factors determined by the antigen and/or the vaccination procedure itself are crucial for the resulting type of immune response. Flt-3L - under circumstances such as the one we have investigated - can also lead to suppression of TH1 T cell immunity, possibly by expansion of immature/unactivated DC.

Modulating vaccine responses with dendritic cells and Toll-like receptors

The immune system is ignorant or even unresponsive to most foreign proteins that are injected in a soluble, deaggregated form, but when injected together with an immune-stimulating agent (i.e. an adjuvant, such as CpG-rich DNA), these foreign proteins can generate robust immunity and long-lived memory to the antigen. In fact, the nature of the adjuvant is what determines the particular type of immune response that follows, which may be biased towards cytotoxic T-cell responses, antibody responses, particular classes of T-helper responses, or antibody isotypes. Clearly, the ability of a vaccine to skew the response toward a particular type is of paramount importance, because different pathogens require distinct types of protective immunities. Therefore, the quest to manipulate the immune system to generate optimally effective immunity against different pathogens can justifiably be considered the 'grand challenge' of modern immunology. Central to this issue is a rare but widely distributed network of cells known as dendritic cells (DCs). DCs, which have been called 'Nature's adjuvants,' express pathogen recognition receptors, such as the Toll-like receptors (TLRs) and C-type lectins, which enable them to sense and respond to microbes or vaccines. Research in the last decade has demonstrated a fundamental role for DCs in initiating and controlling the quality and strength of the immune response. As such, DCs and TLRs represent attractive immune modulatory targets for vaccinologists. The present review provides a summary of emerging themes in the biology DCs and TLRs, with a particular focus on relevance for vaccine development.

Immunological Foundations to the Quest for New Vaccine Adjuvants

Developing efficient adjuvants for human vaccines that elicit broad and sustained immune responses at systemic or mucosal levels remains a formidable challenge for the vaccine industry. Conventional approaches in the past have been largely empirical and--at best--partially successful. Importantly, recent advances in our understanding of the immune system, most particularly with respect to early proinflammatory signals, are leading to the identification of new biological targets for vaccine adjuvants. This review covers both the current status of adjuvant testing in humans, the residual needs for vaccines in development, and the emerging immunological foundations for adjuvant design. A better understanding of the biology of toll-like receptors, non-conventional T cell subpopulations, T and B cell memory, regulatory T cells, and mucosal immunity has profound implications for a modern approach to adjuvant screening and development. The future lies in the high throughput screening of synthetic chemical entities targeting well-characterized biological molecules. Used alone or in combination, such synthetic adjuvants will allow stimulation or modulation in a safe and efficient manner of strong effector, regulatory and memory immune mechanisms.