Keyhole limpet haemocyanin - a model antigen for human immunotoxicological studies

Alpha-1 Antitrypsin-Expressing Mesenchymal Stromal Cells Confer a Long-Term Survival Benefit in a Mouse Model of Lethal GvHD

Acute graft-versus-host disease is a frequent complication associated with allogeneic hematopoietic stem cell transplantation. Patients that become refractory to initial steroid treatment have a poor prognosis. apceth-201 consists of human allogeneic mesenchymal stromal cells, engineered by lentiviral transduction to express the protease inhibitor alpha-1 antitrypsin, to augment the anti-inflammatory potential of the mesenchymal stromal cells. We show that apceth-201 mesenchymal stromal cells efficiently suppress T cell proliferation and polarize macrophages to an anti-inflammatory M2 type, in vitro. To assess the in vivo efficacy of apceth-201, it was tested in two different mouse models of acute graft-versus-host disease. Control animals in a humanized model succumbed quickly to disease, whereas median survival was doubled in apceth-201-treated animals. The product was also tested in a graft-versus-host disease model system that closely mimics haploidentical hematopoietic stem cell transplantation, an approach that is now being evaluated for use in the clinic. Control animals succumbed quickly to disease, whereas treatment with apceth-201 resulted in long-term survival of 57% of the animals. Within 25 days after the second injection, clinical scores returned to baseline in responding animals, indicating complete resolution of graft-versus-host disease. These promising data have led to planning of a phase I study using apceth-201.

Early suppression of B cell immune responses by low doses of chloroquine and pyrimethamine: implications for studying immunity in malaria

Malaria remains a significant worldwide public health problem. To address biological questions, researchers rely on the experimental murine model. For decades, chloroquine (CQ) and pyrimethamine (Pyr) have been used to clear Plasmodium infections in experimental animals using standardised accepted protocols and, because of this, drug-treated controls are rarely included. However, there is limited data available on the modulation of anti-malarial immunity, including generation of memory B cells, when these drugs are administered days after malaria infection. We investigated B cell responses to an important malaria glycolipid, glycosylphosphatidylinositol (GPI), and the hapten nitrophenol (NP), with or without standard CQ and Pyr treatment using the murine model. At day 14, CQ/Pyr treatment significantly suppressed the frequency of NP⁺IgG1⁺ memory B cells in NP-KLH-immunised mice. Furthermore, CQ/Pyr-treated NP-KLH-immunised mice did not have significantly higher cellular counts of NP⁺ B cells, germinal centre B cells, nor NP⁺IgG1⁺ memory B cells than naïve mice (CQ/Pyr treated and untreated). CQ/Pyr-treated GPI-KLH-immunised mice did not have significantly higher cellular counts of GPI⁺ B cells than naïve untreated mice. By day 28, this effect appeared to resolve since all immunised mice, whether treated or untreated, had significantly higher B cell proliferative responses than naïve mice (CQ/Pyr treated and untreated) for the majority of B cell phenotypes. The current study emphasises the potential for drug modulation of antigenic B cell responses when using standardised malaria treatment protocols in the experimental murine model. It is recommended that drug-treated controls are included when using experimental malaria infections to address biological questions.

Exposure to Solar UVR Suppresses Cell-Mediated Immunization Responses in Humans: The Australian Ultraviolet Radiation and Immunity Study

Animal and human studies show that exposure to solar-simulated UVR is immunomodulatory. Human studies that used natural sun exposure and controlled for confounding are rare. We immunized 217 healthy adults (age range = 18-40 years) with a T-cell-dependent antigen, keyhole limpet hemocyanin, and measured personal clothing-adjusted UVR exposure (for 5 days before and after immunization), lifetime cumulative UVR exposure, serum 25-hydroxyvitamin D concentration at immunization, and potential confounding factors. We tested cellular and humoral immune responses in relation to UVR exposure. The delayed-type hypersensitivity response to keyhole limpet hemocyanin recall challenge was lower in individuals with higher personal clothing-adjusted UVR exposure on the day before immunization (P = 0.015) and during intervals spanning the day before to 2-3 days after immunization. There was an incremental increase in T helper type 17 cells (as a proportion of CD4⁺ T cells) from preimmunization to postimmunization in the high, compared with the low, personal clothing-adjusted UVR exposure group (0.31% vs. -0.39%, P = 0.004). Keyhole limpet hemocyanin-specific antibody titers were not associated with acute or cumulative UVR exposure or serum 25-hydroxyvitamin D levels. Higher UVR exposure at antigen sensitization was associated with a reduced delayed-type hypersensitivity response and altered T helper type 17 kinetics. This has implications for the effectiveness of vaccinations and susceptibility to infections that rely on cell-mediated immune responses.

Immunotherapeutic Potential of Mollusk Hemocyanins in Combination with Human Vaccine Adjuvants in Murine Models of Oral Cancer

Mollusk hemocyanins have been used for decades in immunological and clinical applications as natural, nontoxic, nonpathogenic, and nonspecific immunostimulants for the treatment of superficial bladder cancer, as carriers/adjuvants of tumor-associated antigens in cancer vaccine development and as adjuvants to dendritic cell-based immunotherapy, because these glycoproteins induce a bias towards Th1 immunity. Here, we analyzed the preclinical therapeutic potential of the traditional keyhole limpet hemocyanin (KLH) and two new hemocyanins from Concholepas concholepas (CCH) and Fissurella latimarginata (FLH) in mouse models of oral squamous cell carcinoma. Due to the aggressiveness and deadly malignant potential of this cancer, the hemocyanins were applied in combination with adjuvants, such as alum, AddaVax, and QS-21, which have been shown to be safe and effective in human vaccines, to potentiate their antitumor activity. The immunogenic performance of the hemocyanins in combination with the adjuvants was compared, and the best formulation was evaluated for its antitumor effects in two murine models of oral cancer: MOC7 cells implanted in the flank (heterotopic) and bioluminescent AT-84 E7 Luc cells implanted in the floor of the mouth (orthotopic). The results demonstrated that the hemocyanins in combination with QS-21 showed the greatest immunogenicity, as reflected by a robust, specific humoral response predominantly characterized by IgG2a antibodies and a sustained cellular response manifesting as a delayed hypersensitivity reaction. The KLH- and FLH-QS-21 formulations showed reduced tumor development and greater overall survival. Hemocyanins, as opposed to QS-21, had no cytotoxic effect on either oral cancer cell line cultured in vitro, supporting the idea that the antitumor effects of hemocyanins are associated with their modulation of the immune response. Therefore, hemocyanin utilization would allow a lower QS-21 dosage to achieve therapeutic results. Overall, our study opens a new door to further investigation of the use of hemocyanins plus adjuvants for the development of immunotherapies against oral carcinoma.

Clinical Immunotoxicology

Assessment of the potential for a test article to have adverse effects on immune function can be difficult in clinical trials due to a relative lack of useful endpoints. It is therefore common to use a weight of evidence approach with nonclinical studies to indicate if there is a cause for concern that the test article has immunotoxic potential. The most commonly used follow-up assay for immunosuppression is the T-dependent antibody response (TDAR). However, final selection of an assay (or assays) to evaluate potential human immunotoxicity depends on the type of findings in nonclinical studies. For example, signs of unintended immunostimulation or immunomodulation may be assessed using specialized assays using human cells. Other factors should also be considered, such as pharmacology of the test article, potential structural similarities with known immunomodulatory agents, and/or pharmacokinetic/drug disposition findings consistent with accumulation of test article/metabolite in immune system tissues. Although evaluation of the potential for a test article to have adverse effects on immune function can be a complex task, established nonclinical models and some clinical endpoints can be useful to determine the safety of products intended for use as human therapeutics.

Dendritic cell-targeting DNA-based nasal adjuvants for protective mucosal immunity to Streptococcus pneumoniae

To develop safe vaccines for inducing mucosal immunity to major pulmonary bacterial infections, appropriate vaccine antigens (Ags), delivery systems and nontoxic molecular adjuvants must be considered. Such vaccine constructs can induce Ag-specific immune responses that protect against mucosal infections. In particular, it has been shown that simply mixing the adjuvant with the bacterial Ag is a relatively easy means of constructing adjuvant-based mucosal vaccine preparations; the resulting vaccines can elicit protective immunity. DNA-based nasal adjuvants targeting mucosal DCs have been studied in order to induce Ag-specific mucosal and systemic immune responses that provide essential protection against microbial pathogens that invade mucosal surfaces. In this review, initially a plasmid encoding the cDNA of Flt3 ligand (pFL), a molecule that is a growth factor for DCs, as an effective adjuvant for mucosal immunity to pneumococcal infections, is introduced. Next, the potential of adding unmethylated CpG oligodeoxynucleotide and pFL together with a pneumococcal Ag to induce protection from pneumococcal infections is discussed. Pneumococcal surface protein A has been used as vaccine for restoring mucosal immunity in older persons. Further, our nasal pFL adjuvant system with phosphorylcholine-keyhole limpet hemocyanin (PC-KLH) has also been used in pneumococcal vaccine development to induce complete protection from nasal carriage by Streptococcus pneumoniae. Finally, the possibility that anti-PC antibodies induced by nasal delivery of pFL plus PC-KLH may play a protective role in prevention of atherogenesis and thus block subsequent development of cardiovascular disease is discussed.

Immunization enhances the natural antibody repertoire

The role of immunization in the production of antibodies directed against immunogens is widely appreciated in laboratory animals and in humans. However, the role of immunization in the development of "natural antibodies" has not been investigated. Natural antibodies are those antibodies present without known history of infection or immunization, and react to a wide range of targets, including "cryptic" self-antigens that are exposed upon cell death. In this study, the ability of immunization to elicit the production of natural antibodies in laboratory rats was evaluated. Laboratory rats were immunized with a series of injections using peanut extracts (a common allergen), a high molecular weight protein conjugated to hapten (FITC-KLH), and a carbohydrate conjugated to hapten (DNP-Ficall). Significantly greater binding of antibodies from immunized animals compared to controls was observed to numerous autologous organ extracts (brain, kidney, liver, lung, prostate, and spleen) for both IgM and IgG, although the effect was more pronounced for IgM. These studies suggest that immunization may have at least one unforeseen benefit, enhancing networks of natural antibodies that may be important in such processes as wound repair and tumor surveillance. Such enhancement of natural antibody function may be particularly important in Western society, where decreased exposure to the environment may be associated with a weakened natural antibody repertoire.

Monitoring of dynamic changes in Keyhole Limpet Hemocyanin (KLH)-specific B cells in KLH-vaccinated cancer patients

Keyhole limpet hemocyanin (KLH) is used as an immunogenic neo-antigen for various clinical applications and during vaccine development. For advanced monitoring of KLH-based interventions, we developed a flow cytometry-based assay for the ex vivo detection, phenotyping and isolation of KLH-specific B cells. As proof-of-principle, we analyzed 10 melanoma patients exposed to KLH during anti-cancer dendritic cell vaccination. Our assay demonstrated sensitive and specific detection of KLH-specific B cells in peripheral blood and KLH-specific B cell frequencies strongly correlated with anti-KLH serum antibody titers. Profiling of B cell subsets over the vaccination course revealed that KLH-specific B cells matured from naïve to class-switched memory B cells, confirming the prototypic B cell response to a neo-antigen. We conclude that flow-cytometric detection and in-depth phenotyping of KLH-specific B cells is specific, sensitive, and scalable. Our findings provide novel opportunities to monitor KLH-specific immune responses and serve as a blueprint for the development of new flow-cytometric protocols.

Evaluating the potential of the GFAP-KLH immune-tolerizing vaccine for type 1 diabetes in mice

Glial fibrillary acidic protein (GFAP), expressed in peri-islet Schwann cells, is a novel target for the treatment of type 1 diabetes mellitus (T1DM). We designed a GFAP immune-tolerizing vaccine that successfully suppresses hyperglycemia and enhances C peptide secretion. The GFAP vaccine significantly prevented T cell infiltration into pancreatic islets. Moreover, after GFAP vaccination, naïve T-cell differentiation shifted from a cytotoxic Th1- to a Th2-biased humoral response. These results indicate that as a novel target, GFAP reliably predicts the development of T1DM, and that the GFAP vaccine successfully delays the progression of T1DM by regulating T-cell differentiation.