Effect of DETOX as an adjuvant for melanoma vaccine

Monophosphoryl Lipid A-Rhamnose Conjugates as a New Class of Vaccine Adjuvants

Adjuvant is an integral part of all vaccine formulations but only a few adjuvants with limited efficacies or application scopes are available. Thus, developing more robust and diverse adjuvants is necessary. To this end, a new class of adjuvants having α- and β-rhamnose (Rha) attached to the 1- and 6'-positions of monophosphoryl lipid A (MPLA) was designed, synthesized, and immunologically evaluated in mice. The results indicated a synergistic effect of MPLA and Rha, two immunostimulators that function via interacting with toll-like receptor 4 and recruiting endogenous anti-Rha antibodies, respectively. All the tested MPLA-Rha conjugates exhibited potent adjuvant activities to promote antibody production against both protein and carbohydrate antigens. Overall, MPLA-α-Rha exhibited better activities than MPLA-β-Rha, and 6'-linked conjugates were slightly better than 1-linked ones. Particularly, MPLA-1-α-Rha and MPLA-6'-α-Rha were the most effective adjuvants in promoting IgG antibody responses against protein antigen keyhole limpet hemocyanin and carbohydrate antigen sTn, respectively.

Monophosphoryl lipid A (MPL) as an adjuvant for anti-cancer vaccines: clinical results

As technological advances allow for the identification of tumor-associated antigens (TAAs) against which adaptive immune responses can be raised, efforts to develop vaccines for the treatment of cancer continue to gain momentum. Some of these vaccines target differentiation antigens that are expressed by tumors derived from one particular tissue (e. g., Melan-A/ MART-1, tyrosinase, gp 100). Some target antigens are specifically expressed in tumors of different types but not in normal tissues (e. g., MAGE-3), while other possible targets are antigens that are expressed at low level in normal tissues and are over-expressed in tumors of different types (e. g., HER2, Muc 1). Oncogenes (HER2/neu, Ras, E7 HPV 16), tumor suppressor genes (pS3) or tumor-specific post-translational modified proteins (under glycosylated Muc 1) can also be used as cancer vaccine candidates. In either case, these antigens tend to be poorly inmmunogenic by themselves and vaccines containing them generally require the inclusion of potent immunological adjuvants in order to generate robust anti-tumor immune responses in humans. Many adjuvants currently under evaluation for use in cancer vaccines activate relevant antigen presenting cells, such as dendritic cells and macrophages, via toll-like receptors (TLRs) and promote effective uptake, processing and presentation of antigen to T-cells in draining lymph nodes.Lipid A, the biologically active portion of the gram-negative bacterial cell wall constituent lipopolysaccharide (LPS), is known to possess strong immunostimulatory properties and has been evaluated for more than two decades as an adjuvant for promoting immune responses to minimally immunogenic antigens, including TAAs. The relatively recent discovery of TLRs and the identification of TLR4 as the signaling receptor for lipid A have allowed for a better understanding of how this immunostimulant functions with regard to induction of innate and adaptive immune responses.Although several lipid A species, including LPS and synthetic analogs, have been developed and tested as monotherapeutics for the treatment of cancer,1-8 only 3-O-desacyl-4'-monophosphoryl lipid A (MPL) has been evaluated as a cancer vaccine adjuvant in published human clinical trials. MPL comprises the lipid A portion of Salmonella minnesota LPS from which the (R)-3-hydroxytetrade canoyl group and the l-phosphare have been removed by successive acid and base hydrolysis.9 LPS and MPL induce similar cytokine profiles, but MPLis at least 1OO-fold less toxic.9,10 lOMPL has been administered to more than 300, 000 human subjects in studies of next-generation vaccines.11 In this chapter, published clinical trials conducted to evaluate the safety and/or efficacy of various cancer vaccines containing MPL, either alone or combined with other immunostimulants, Such as cell wall skeleton (CWS) of Mycobacterium phlei in the adjuvant Detox; Biomira, Inc.), the saponin QS-21 (in the adjuvants AS01B and AS02B; GSK Biologicals) or with QS-21 and CpG oligonucleotides (in the adjuvant AS15; GSK Biologicals) will be summarized. Combining MPL with other immunostimulants has been demonstrated to be advantageous in many cases and may be required to elicit the full complement of activities necessary to achieve an effective immune response and overcome the ability of tumors to evade attack by the immune system. In this chapter, information relating to vaccines targeting specific cancers will be presented in the first section, while information relating to vaccines targeting multiple tumor types by the induction of immune responses to shared TAAs is presented in the second section.

Delivery strategies of melanoma vaccines: an overview

For many years, various cancer vaccines have been widely evaluated, however clinical responses remain rare. In this review, we attempt to address the question of which delivery strategies and platforms are feasible to produce clinical response and define the characteristics of the strategy that will induce long-lasting antitumor response. We limit our analysis and discussion to microparticles/nanoparticles, liposomes, heat-shock proteins, viral vectors and different types of adjuvants. This review aims to provide an overview of the specific characteristics, strengths and limitations of these delivery systems, focusing on their impacts on the development of melanoma vaccine. To date, only adoptive T-cell transfer has shown promising clinical outcomes compared to other treatments.

Tumor Cell Vaccines

This chapter reviews the history of tumor cell vaccines, both autologous and allogeneic, as well as adjuvants used with tumor cell vaccines. The chapter discusses various tumor cell modifications that have been tested over the years. The immune response to tumor vaccines is briefly described, as are some methods of immune monitoring after vaccine therapy. Finally, there is a description of various tumor cell-based vaccines that have been tested in clinical trials.

Cancer vaccines entering Phase III clinical trials

The last 10 years have seen a growth in the number of tumour antigens identified from immune responses raised in patients. The discovery that tumours can be recognised by the immune system stimulated a great deal of work characterising the molecular mechanisms underlying immune recognition. This in turn has led to an impressive array of immunological approaches to the generation of cancer vaccines; these range from molecularly defined T cell epitopes, antibody-based vaccines, cytokine therapies, immune modulators and DNA vaccines, to whole cell vaccines and, more recently, combinations of these methods. Many of these approaches have entered Phase I/II trials and have shown interesting clinical results. Moreover, they have extended our knowledge of the immune system and our understanding of the mechanisms required to design a successful cancer vaccine. This review outlines some of the approaches that have led to some of these vaccines entering Phase III clinical trials, discusses their modes of action and reports on their current status in trial.

Experimental squalene adjuvant

Model experiments on laboratory animals (guinea pigs) were carried out to test the possible allergic reaction (possibility of sensitisation) to the repeated administration of an experimental lipoid adjuvant prepared on the basis of squalene (experimental squalene adjuvant--ESA). No significant differences were observed between the animals sensitised-provoked with ESA and control animals. In order to evaluate the local tissue reactivity (local reactogenity), also with regard to the process dynamics to the administration of ESA, comparative patho-anatomical and patho-histological examinations of tissues were carried out in the location of adjuvant administration. The examinations indicated very low local reactogenity of the experimental lipoid adjuvant prepared in our laboratory. The test of pyrogenicity also confirmed the safety of ESA, the labelled lysate sensitivity lambda was under 0.25 IU/cm3.

Adjuvants in veterinary vaccines: modes of action and adverse effects

Vaccine adjuvants are chemicals, microbial components, or mammalian proteins that enhance the immune response to vaccine antigens. Interest in reducing vaccine-related adverse effects and inducing specific types of immunity has led to the development of numerous new adjuvants. Adjuvants in development or in experimental and commercial vaccines include aluminum salts (alum), oil emulsions, saponins, immune-stimulating complexes (ISCOMs), liposomes, microparticles, nonionic block copolymers, derivatized polysaccharides, cytokines, and a wide variety of bacterial derivatives. The mechanisms of action of these diverse compounds vary, as does their induction of cell-mediated and antibody responses. Factors influencing the selection of an adjuvant include animal species, specific pathogen, vaccine antigen, route of immunization, and type of immunity needed.

Survey of human-use adjuvants

Although there are only four adjuvants used in licensed vaccines for humans, a wealth of information on novel vaccine adjuvants has become available in both animal models and clinical studies over the past decade. Many vaccine candidates require immunopotentiation to achieve a satisfactory immune response, which is driving the search for new and safer approaches. In this review, we take a brief look at what is known of the mechanisms of action, consider some of the elements of product development, then survey several of the classes of adjuvants within the context of human trials.

Malignant melanoma: current state of primary and adjuvant treatment

Metastatic malignant melanoma remains a highly lethal disease with an incidence that continues to rise. Management of melanoma includes definitive local, regional and distant control. There is substantial prospective and retrospective data to base the extent of both primary as well as adjuvant therapy. The results of these trials have on occasion been at odds. A critical assessment of the available information pertaining to the adjuvant treatment of cutaneous melanoma is needed. This review provides a critical assessment of the current data that is available to guide both primary resection as well as adjuvant therapy. To date, current trials have shown little promise with nonspecific immunostimulants and cytotoxic chemotherapy. In contrast, dose interferon-alpha2b has been shown to improve relapse-free survival and likely improves melanoma-specific survival as well. Based on the available data, interferon-alpha2b remains the adjuvant therapy of choice for high-risk patients treated outside clinical trials, and the appropriate control arm for clinical trials evaluating new or modified adjuvant regimens.

The development and use of vaccine adjuvants

Interest in vaccine adjuvants is intense and growing, because many of the new subunit vaccine candidates lack sufficient immunogenicity to be clinically useful. In this review, I have emphasized modern vaccine adjuvants injected parenterally, or administered orally, intranasally, or transcutaneously with licensed or experimental vaccines in humans. Every adjuvant has a complex and often multi-factorial immunological mechanism, usually poorly understood in vivo. Many determinants of adjuvanticity exist, and each adjuvanted vaccine is unique. Adjuvant safety is critical and can enhance, retard, or stop development of an adjuvanted vaccine. The choice of an adjuvant often depends upon expensive experimental trial and error, upon cost, and upon commercial availability. Extensive regulatory and administrative support is required to conduct clinical trials of adjuvanted vaccines. Finally, comparative adjuvant trials where one antigen is formulated with different adjuvants and administered by a common protocol to animals and humans can accelerate vaccine development.

Adjuvant immunotherapy of resected, intermediate-thickness, node-negative melanoma with an allogeneic tumor vaccine: overall results of a randomized trial of the Southwest Oncology Group

PURPOSE

Patients with clinically negative nodes constitute over 85% of new melanoma cases. There is no adjuvant therapy for intermediate-thickness, node-negative melanoma patients.

PATIENTS AND METHODS

The Southwest Oncology Group conducted a randomized phase III trial of an allogeneic melanoma vaccine for 2 years versus observation in patients with intermediate-thickness (1.5 to 4.0 mm or Clark's level IV if thickness unknown), clinically or pathologically node-negative melanoma (T3N0M0).

RESULTS

Six hundred eighty-nine patients were accrued over 4.5 years; 89 patients (13%) were ineligible. Surgical node staging was performed in 24%, the remainder were clinical N0. Thirteen eligible patients refused assigned treatment: seven on the observation arm and six on the vaccine arm. Most vaccine patients experienced mild to moderate local toxicity, but 26 (9%) experienced grade 3 toxicity. After a median follow-up of 5.6 years, there were 107 events (tumor recurrences or deaths) among the 300 eligible patients randomized to vaccine compared with 114 among the 300 eligible patients randomized to observation (hazard ratio, 0.92; Cox-adjusted P(2) = 0.51). There was no difference in vaccine efficacy among patients with tumors < or = 3 mm or > 3 mm.

CONCLUSION

This represents one of the largest randomized, controlled trials of adjuvant vaccine therapy in human cancer reported to date. Compliance with randomization was excellent, with only 2% refusing assigned therapy. There is no evidence of improved disease-free survival among patients randomized to receive vaccine, although the power to detect a small but clinically significant difference was low. Future investigations of adjuvant vaccine approaches for patients with intermediate-thickness melanoma should involve larger numbers of patients and ideally should include sentinel node biopsy staging.

Transcutaneous immunization using colonization factor and heat-labile enterotoxin induces correlates of protective immunity for enterotoxigenic Escherichia coli

Enterotoxigenic Escherichia coli (ETEC) diarrheal disease is a worldwide problem that may be addressed by transcutaneous delivery of a vaccine. In several human settings, protective immunity has been associated with immune responses to E. coli colonization factors and to the heat-labile toxin that induces the diarrhea. In this set of animal studies, transcutaneous immunization (TCI) using recombinant colonization factor CS6 and cholera toxin (CT) or heat-labile enterotoxin (LT) as the adjuvant induced immunoglobulin G (IgG) and IgA anti-CS6 responses in sera and stools and antibody responses that recognized CS6 antigen in its native configuration. The antitoxin immunity induced by TCI was also shown to protect against enteric toxin challenge. Although immunization with LT via the skin induced mucosal secretory IgA responses to LT, protection could also be achieved by intravenous injection of the immune sera. Finally, a malaria vaccine antigen, merzoite surface protein 1(42) administered with CT as the adjuvant, induced both merzoite surface protein antibodies and T-cell responses while conferring protective antitoxin immunity, suggesting that both antiparasitic activity and antidiarrheal activity can be obtained with a single vaccine formulation. Overall, our results demonstrate that relevant colonization factor and antitoxin immunity can be induced by TCI and suggest that an ETEC traveler's diarrhea vaccine could be delivered by using a patch.

Optimization of intracerebral tumour protection by active-specific immunization against murine melanoma B16/G3.12

Development of brain metastases despite extracerebral response to systemic immunotherapy is a common problem in melanoma patients. We have previously described a murine melanoma vaccine of interferon-gamma (IFNgamma)-treated, irradiated syngeneic B16/G3.12 and allogeneic (Cloudman) melanoma cells, plus the adjuvant DETOX, that is protective against subcutaneous (93%) or intracerebral (69%) syngeneic challenge. This study aimed to optimize this vaccine. Groups of nine or 10 mice were immunized five times in 5 weeks with: (i) complete vaccine +/- IFNgamma (VAC+, VAC-); (ii) syngeneic 2 x 106 G3.12 cells plus DETOX (Syn+D), (iii) 2 x 106 allogeneic Cloudman cells plus DETOX (Allo+D); (iv) VAC+ without DETOX (no DETOX); (v) DETOX alone (DETOX); or (vi) phosphate buffered saline (PBS). Mice were challenged subcutaneously with 104 viable G3.12 (or Cloudman cells) and after 35 days intracerebrally with 104 G3.12 cells. Expression of H-2 antigens (measured using fluorescence-activated cell sorting), splenocyte cytotoxicity (measured using 51Cr release) and median overall survival (OAS) were analysed using the log-rank test. VAC+, VAC- and G3.12 mice were equally protected from subcutaneous (s.c.) and intracerebral (i.c.) melanoma challenge (OAS 65 days for s.c., 30 days for i.c.). Protection was less (P < 0.05) in DETOX mice (48 days for s.c.), PBS mice (47 days for s.c., 21 days for i.c.) or no DETOX mice (51 days for s.c.). Allo+D mice showed s.c. (59 days) but not i.c. protection (20 days). IFNgamma incubation did not increase the effect in either the challenge cells or the vaccine cells (P > 0.05). Specific cytotoxicity was seen with G3.12 targets in VAC+ (27%) but not PBS (2%; P < 0.05) mice with equal NK (YAC-1) lysis (10% versus 7%; P< 0.05). Optimal protection against s.c./i.c. experimental murine melanoma was yielded by irradiated syngeneic cells plus DETOX. DETOX alone was not active. Upregulation of H-2 antigens with IFNgamma under these conditions does not augment protection.

Enhanced dendritic cell maturation by TNF-alpha or cytidine-phosphate-guanosine DNA drives T cell activation in vitro and therapeutic anti-tumor immune responses in vivo

Dendritic cells (DC) manipulated ex vivo can induce tumor immunity in experimental murine tumor models. To improve DC-based tumor vaccination, we studied whether DC maturation affects the T cell-activating potential in vitro and the induction of tumor immunity in vivo. Maturation of murine bone marrow-derived DC was induced by GM-CSF plus IL-4 alone or by further addition of TNF-alpha or a cytidine-phosphate-guanosine (CpG)-containing oligonucleotide (ODN-1826), which mimics the immunostimulatory effect of bacterial DNA. Flow cytometric analysis of costimulatory molecules and MHC class II showed that DC maturation was stimulated most by ODN-1826, whereas TNF-alpha had an intermediate effect. The extent of maturation correlated with the secretion of IL-12 and the induction of alloreactive T cell proliferation. In BALB/c mice, s.c. injection of colon carcinoma cells resulted in rapidly growing tumors. In this model, CpG-ODN-stimulated DC cocultured with irradiated tumor cells also induced prophylactic protection most effectively and were therapeutically effective when administered 3 days after tumor challenge. Thus, CpG-ODN-enhanced DC maturation may represent an efficient means to improve clinical tumor vaccination.

Newer strategies for effective evaluation of primary melanoma and treatment of stage III and IV disease

Our objective in this article is to update dermatologists on the clinical management of malignant melanoma, including the role of sentinel node biopsy and options for the treatment of stage III and stage IV disease. The role of the dermatologist throughout the continuum of care is emphasized, and the essential partnership with medical oncology in recognizing promising new options for patients with advanced disease is examined.

Keyhole limpet hemocyanin (KLH): a biomedical review

In this review we present a broad survey of fundamental scientific and medically applied studies on keyhole limpet hemocyanin (KLH). Commencing with the biochemistry of KLH, information on the biosynthesis and biological role of this copper-containing respiratory protein in the marine gastropod Megathura crenulata is provided. The established methods for the purification of the two isoforms of KLH (KLH1 and KLH2) are then covered, followed by detailed accounts of the molecular mass determination, functional unit (FU) structure, carbohydrate content, immunological analysis and recent aspects of the molecular genetics of KLH. The transmission electron microscope (TEM) has contributed significantly to the understanding of KLH structure, primarily from negatively stained images. We give a brief account of TEM studies on the native KLH oligomers, the experimental manipulation of the oligomeric states, together with immunolabelling data and studies on subunit reassociation. The field of cellular immunology has provided much relevant biomedical information on KLH and has led to the expansion of use of KLH in experimental immunology and clinically as an immunotherapeutic agent; this area is presented in some detail. The major clinical use of KLH is specifically for the treatment of bladder carcinoma, with efficacy probably due to a cross-reacting carbohydrate epitope. KLH also has considerable possibilities for the treatment of other carcinomas, in particular the epithelially derived adenocarciomas, when used as a carrier for carcinoma ganglioside and mucin-like epitopes. The widespread use of KLH as a hapten carrier and generalised vaccine component represent other major on-going aspects of KLH research, together with its use for the diagnosis of Schistosomiasis, drug assay and the treatment of drug addiction. Immune competence testing, assessment of stress and the understanding of inflammatory conditions are other areas where KLH is also making a useful contribution to medical research.

Immunization with recombinant class 1 outer-membrane protein from Neisseria meningitidis: influence of liposomes and adjuvants on antibody avidity, recognition of native protein and the induction of a bactericidal immune response against meningococci

The porA gene from Neisseria meningitidis was cloned into the pRSETA vector and recombinant class 1 outer-membrane protein expressed at high levels in Escherichia coli. The protein was readily purified by affinity chromatography on a Ni2+ matrix and used for immunization of mice with conventional AI(OH)3 adjuvant, with experimental adjuvants which have the potential for human use, and with liposomes. The resulting sera were analysed for the magnitude, subclass distribution and antigenic specificity of the immune response. In addition, surface plasmon resonance (SPR) was used to quantify antibody avidity by analysis of the kinetics of binding to native class 1 protein. Immunization with conventional and experimental adjuvants induced antibodies of low avidity that did not recognize native class 1 protein. In contrast, immunization with recombinant protein in liposomes induced antibodies of high avidity which recognized native class 1 protein, as measured by their ability to label meningococcal cells in immunofluorescence assays and to inhibit the binding of a protective mAb. These properties were associated with the presence in sera of high levels of antibodies with the ability to induce complement-mediated killing of meningococci. These data show that liposomes containing recombinant class 1 protein represent a potential basis of future vaccines, of defined composition, designed for the prevention of group B meningococcal infections.

Experimental rationale for treatment of high-risk human melanoma with zinc chloride fixative paste. Increased resistance to tumor challenge in murine melanoma model

BACKGROUND

Fixed-tissue micrographic surgery (Mohs) of melanoma has been shown by retrospective analysis to improve 5-year survival.

OBJECTIVES

To determine whether zinc chloride fixative paste acts as an immune adjuvant to increase host resistance to melanoma.

METHODS

We performed a murine study using the poorly immunogenic B16 melanoma of C57Bl6J mice, and the more immunogenic K1735p melanoma of C3H/HeN mice. Tumors were treated with zinc chloride paste and excised 24 hours later (Group 1), or simply excised (Group 2). Mice were challenged 7 days later with injection of melanoma cells at a distant site, and tumor growth in this second site was followed.

RESULTS

K1735p melanomas developed at the challenge site in 69% of mice treated with excision versus 32% of mice treated with zinc chloride fixation (P < 0.025). Development of B16 melanoma was not altered by zinc chloride fixation.

CONCLUSION

Zinc chloride fixation of the more immunogenic K1735p melanoma increased resistance to subsequent tumor challenge, suggesting that zinc chloride fixative paste acts as an immune adjuvant.

Enhancement of tumour response to photodynamic therapy by adjuvant mycobacterium cell-wall treatment

Mycobacterium cell-wall extract (MCWE) is a potent non-specific immunostimulant that elicits a local inflammatory response associated with antitumour activity. Tumour-localized administration of MCWE has been examined as an adjuvant to photodynamic therapy (PDT) mediated by the photosensitizers Photofrin, benzoporphyrin derivative monoacid (BPD), metatetrahydroxyphenylchlorin (mTHPC), or zinc (II)-phthalocyanine (ZnPc). A single MCWE treatment, given immediately after light treatment of murine EMT6 tumours, potentiates the curative effect of PDT. A similar enhancement of tumour response to Photofrin-based PDT is obtained with the live Bacillus Calmette-Guérin (BCG) vaccine. Despite differences in the kinetics/intensity of damage induction to tumour microvasculature and other characteristics underlying the mechanism of antitumour activity of Photofrin, BPD, mTHPC and ZnPc, there appear to be no marked differences in the therapeutic benefit of adjuvant MCWE therapy combined with the PDT mediated by these various photosensitizers. This may be related to the fact that MCWE elicits a wide range of immunomodulatory effects that could amplify and sustain the inflammatory/immune responses triggered by PDT. The enhancement of inflammatory effector cell activity is indicated by the increased infiltration of neutrophils and other myeloid cells at the expense of malignant cells found in the MCWE plus mTHPC-based PDT treatment group compared to the PDT-only group.

Adjuvants--a classification and review of their modes of action

Since early this century, various substances have been added to vaccines and certain formulations have been devised in an attempt to render vaccines more effective. Despite a plethora of options, only aluminium salts have gained acceptance as human vaccine adjuvants and even veterinary vaccines are largely dependent upon the use of aluminium salts. Currently, many new vaccines are under development and there is a desire to simplify vaccination schedules both by increasing the number of components per vaccine and decreasing the number of doses required for a vaccine course. New, more effective adjuvants will be required to achieve this.

ISCOMs (immunostimulating complexes): the first decade

A little over a decade ago, novel immunostimulating complexes (ISCOMs) were described. This review examines the position and progress that ISCOM technology has achieved in the fields of vaccine research and medicine over this period. Much of the work on ISCOMs has remained in the area of vaccine research where there is still an urgent need for improved adjuvants to help combat important diseases such as AIDS, malaria and influenza. Currently the only widely licensed adjuvants for human use are the aluminium salts, but with the trend towards highly purified subunit vaccines, which are inherently less immunogenic than some of the older vaccines, potent adjuvants capable of promoting specific immune responses are required. ISCOMs are one such technology that offers many of these requirements and as their use in vaccines enters its second decade clinical trials are commencing that will establish whether these submicron, non-living particles composed of saponin, cholesterol, phospholipid and in many cases protein, are useful components for a range of human vaccines.