Targeting of the non-mutated tumor antigen HER2/neu to mature dendritic cells induces an integrated immune response that protects against breast cancer in mice

INTRODUCTION

Given their relative simplicity of manufacture and ability to be injected repeatedly, vaccines in a protein format are attractive for breast and other cancers. However, soluble human epidermal growth factor receptor (HER2)/neu protein as a vaccine has not been immunogenic. When protein is directly targeted to antigen uptake receptors, such as DEC205 (DEC), efficient processing and presentation of antigen take place. The aim of this study was to determine the immunogenicity of a HER2 protein vaccine that directly targets to DEC+ dendritic cells (DCs) in a mouse breast cancer model.

METHODS

We genetically engineered the HER2 extracellular domain into a monoclonal antibody specific for DEC (DEC-HER2). Mice of various genetic backgrounds were immunized with DEC-HER2 in combination with DC maturation stimuli (poly IC ± CD40 Ab). Vaccine-induced T cell immunity was determined by analyzing the ability of CD4+/CD8+ T cell to produce interferon (IFN)-gamma and proliferate upon antigen rechallenge. Sera were assessed for the presence of antigen specific antibody (Ab). For vaccine efficacy, FVB/N mice were immunized with DEC-HER2 in combination with poly IC and protection against neu-expressing mammary tumors was assessed. Protection mechanisms and tumor-specific T cell responses were also evaluated.

RESULTS

We demonstrate that DEC-HER2 fusion mAb, but not Ctrl Ig-HER2, elicits strong, broad and multifunctional CD4+ T cell immunity, CD8+ T cell responses, and humoral immunity specific for HER2 antigen. Cross-reactivity to rat neu protein was also observed. Importantly, mice xeno-primed with DEC-HER2 were protected from a neu-expressing mammary tumor challenge. Both CD4+ and CD8+ T cells mediated the tumor protection. Robust anti-tumor T cell immunity was detected in tumor protected mice.

CONCLUSIONS

Immunization of mice with HER2 protein vaccine targeting DEC+ DCs in vivo induced high levels of T- and B-cell immunity. Non-targeted HER2 protein was poorly immunogenic for CD4+ and CD8+ T cells. This vaccination approach provided long-term survival benefit for mice challenged with neu-expressing tumor following as little as 2.7 μg of HER2 protein incorporated in the vaccine. Vaccine-induced CD4+ and CD8+ T cells were both essential for tumor protection. This immunization strategy demonstrates great potential towards the development of vaccines for breast cancer patients.

The human cancer antigen mesothelin is more efficiently presented to the mouse immune system when targeted to the DEC-205/CD205 receptor on dendritic cells

To develop a tumor vaccine directly targeting tumor antigen to dendritic cells in situ, we engineered human mesothelin (MSLN) into an antibody specific for mouse DEC-205, a receptor for antigen presentation. We then characterized both T cell and humoral responses to human MSLN and compared immunizing efficacy of DEC-205-targeted MSLN to nontargeted protein after a single-dose immunization. Targeting human MSLN to DEC-205 receptor induced stronger CD4(+) T-cell responses compared to high doses of mesothelin protein. Approximately 0.5% CD4(+) T cells were primed to produce IFN-gamma, tumor necrosis factor-alpha, and IL-2 via intracellular cytokine staining, and the T cells also could proliferate rapidly. The immune response exhibited breadth because the primed CD4(+) T cells responded to at least three epitopes in the H-2(b) background. Targeting MSLN protein to DEC-205 receptor also resulted in cross-presentation to CD8(+) T cells. Antibody responses against human MSLN were also detected in serum from primed mice by ELISA assays. In summary, targeting of MSLN to DEC-205 improves the induction of CD4(+) and CD8(+) T-cell immunity accompanied by an antibody response. DEC-205-targeting could be valuable for enhancing immunity to MSLN in cancers where this nonmutated protein is expressed.

Defining the interaction of the Treponema pallidum adhesin Tp0751 with laminin

Various invasive pathogens attach to host tissues via the extracellular matrix component laminin, the major glycoprotein found within basement membranes. Previous investigations identified the laminin-binding adhesin Tp0751 within the spirochete bacterium Treponema pallidum. In the current study, Tp0751 was shown to attach to a variety of laminin isoforms that are widely distributed throughout the host, including laminins 1, 2, 4, 8, and 10. Such universal attachment is conducive for an adhesin present within a highly invasive pathogen that encounters a variety of tissue sites during the course of infection. Additional studies systematically identified the amino acid residues within Tp0751 that contribute to laminin binding using synthetic peptides designed from the mature protein sequence. The minimum laminin-binding region of the adhesin was localized to 10 amino acids; peptides containing these residues inhibited attachment of Tp0751 and T. pallidum to laminin. Further, Tp0751-specific antibodies inhibited attachment of T. pallidum to laminin. This study furthers our knowledge of the interaction of T. pallidum with laminin, an association that is proposed to facilitate bacterial traversal of basement membranes and subsequent entry into the circulation and tissue invasion. As such, these investigations will reveal new targets for possible prevention of bacterial dissemination and establishment of chronic infection.

Treponema pallidum fibronectin-binding proteins

Putative adhesins were predicted by computer analysis of the Treponema pallidum genome. Two treponemal proteins, Tp0155 and Tp0483, demonstrated specific attachment to fibronectin, blocked bacterial adherence to fibronectin-coated slides, and supported attachment of fibronectin-producing mammalian cells. These results suggest Tp0155 and Tp0483 are fibronectin-binding proteins mediating T. pallidum-host interactions.

Ultrastructure of a novel eurytele nematocyst of Carybdea alata Reynaud (Cubozoa, Cnidaria)

The ultrastructural characteristics of nematocysts from the cubozoan Carybdea alata Reynaud, 1830 (Hawaiian box jellyfish) were examined using light, scanning and transmission electron microscopy. We reclassified the predominant nematocyst in C. alata tentacles as a heterotrichous microbasic eurytele, based on spine, tubule and capsule measurements. These nematocysts exhibited a prominent and singular stylet, herein referred to as the lancet. Discharged nematocysts from fixed tentacle preparations displayed the following structures: a smooth shaft base, lamellae, a hemicircumferential fissure demarking the proximal end of a stratified lancet, and a gradually tapering tubule densely covered with large triangularly shaped spines. The lancet remained partially adjoined to the shaft base in a hinge-like fashion in rapidly fixed, whole-tentacle preparations. In contrast, this structure was not observed in discharged nematocyst preparations which involved multiple transfer steps prior to fixation. Various approaches were designed to detect this structure in the absence of fixative. Detached lancets were located in proximity to discharged tubules in undisturbed coverslip preparations of fresh tentacles. In addition, examination of embedded nematocysts from fresh tentacles laid on polyacrylamide gels revealed still-attached lancets. To examine the function of this structure in prey capture, Artemia sp. laden tentacles were prepared for scanning electron microscopy. While carapace exteriors exhibited structures proximal to the lancet, i.e., the nematocyst capsule and shaft base, neither tubule nor lancet structures were visible. Taken together, the morphological data suggested a series of events involved in the discharge of a novel eurytele from C. alata.