Immunogenicity and Therapeutic Efficacy of a Dual-Component Genetic Cancer Vaccine Cotargeting Carcinoembryonic Antigen and HER2/neu in Preclinical Models

Abstract

Several cancer vaccine efforts have been directed to simultaneously cotarget multiple tumor antigens, with the intent to achieve broader immune responses and more effective control of cancer growth. Genetic cancer vaccines based on in vivo muscle electro-gene-transfer of plasmid DNA (DNA-EGT) and adenoviral vectors represent promising modalities to elicit powerful immune responses against tumor-associated antigens (TAAs) such as carcinoembryonic antigen (CEA) and human epidermal growth factor receptor-2 (HER2)/neu. Combinations of these modalities of immunization (heterologous prime-boost) can induce superior immune reactions as compared with single-modality vaccines. We have generated a dual component-dual target genetic cancer vaccine consisting of a DNA moiety containing equal amounts of two plasmids, one encoding the extracellular and transmembrane domains of HER2 (ECD.TM) and the other encoding CEA fused to the B subunit of Escherichia coli heat-labile toxin (LTB), and of an adenoviral subtype 6 dicistronic vector carrying the same two tumor antigens gene constructs. The CEA/HER2 vaccine was tested in two different CEA/HER2 double-transgenic mouse models and in NOD/scid-DR1 mice engrafted with the human immune system. The immune response was measured by enzyme-linked immunospot assay, flow cytometry, and ELISA. The CEA/HER2 vaccine was able to break immune tolerance against both antigens. Induction of a T cell and antibody immune response was detected in immune-tolerant mice. Most importantly, the vaccine was able to slow the growth of HER2/neu⁺ and CEA⁺ tumors. A significant T cell response was measured in NOD/scid-DR1 mice engrafted with human cord blood cells. In conclusion, the CEA/HER2 genetic vaccine was immunogenic and able to confer significant therapeutic effects. These data warrant the evaluation of this vaccination strategy in human clinical trials.

Evolution of animal models in cancer vaccine development

“…Using a bicistronic carcinoembryonic antigen (CEA)/HER2 DNA vaccine (V932), we showed reactivity to both antigens in HER2/CEA dual Tg mice [46]. The feasibility of dual targeted DNA vaccines is encouraging and may lead to the advent of multi-targeted vaccines.…”

Superior Immunologic and Therapeutic Efficacy of a Xenogeneic Genetic Cancer Vaccine Targeting Carcinoembryonic Human Antigen

“…One drawback of the study was that an heterogeneous patient population in terms of tumor types and clinical stage was enrolled in the trial. While the immune enhancing properties of LTB in rodent species have been clearly assessed by our group, 18,23 this clinical study did not address whether this adjuvant can enhance the immune response against a fused antigen in humans. In contrast, rhCEA is devoid of nonself portions of viral or bacterial origin and may act as a pure xeno-antigen by means of the mechanisms here described.…”

“…17 The two technologies can be combined together in heterologous prime-boost modalities to increase the level of immunogenicity and allow repeated boosting in order to maintain elevated levels of immune responses to target antigen(s) if necessary. 15,18 We have previously reported the cloning and characterization of the rhesus homolog of human CEA (hCEA). Rhesus CEA (rhCEA) encodes a protein of 705 amino acids that is 78.9% homologous to hCEA.…”

Cargo-Delivery Platforms for Targeted Delivery of Inhibitor Cargos Against Botulism

“…Alternatively, again using CT as an example, the cargo could be transported through a direct fusion to the B domain. This approach has been used primarily for cancer therapy [149–150] and vaccine antigen delivery [151–152]. For a retrograde transport-based delivery that is neuron specific to be realized, a neuron-specific binding domain must be incorporated into the delivery vehicle.…”