Vaccination with Cytoplasmic ErbB-2 DNA Protects Mice from Mammary Tumor Growth Without Anti-ErbB-2 Antibody

Abstract

Wild-type ErbB-2 (E2) positive D2F2/E2 tumors are rejected by active vaccination with ErbB-2 DNA. However, anti-ErbB-2 Ab response can cause cardiac toxicity or interfere with cellular immunity. It will be advantageous to induce only cellular immunity by active vaccination. A panel of E2 DNA vaccines were constructed, and their vaccination efficacy was ranked as E2 > tyrosine kinase-deficient ErbB-2 (E2A) > full-length ErbB-2 targeted to the cytoplasm (cytE2) > tyrosine kinase-deficient cytE2 (cytE2A). E2A is a tyrosine kinase-deficient mutant containing a single residue substitution. CytE2 or cytE2A encodes a full-length protein that is targeted to and rapidly degraded in the cytosol by the proteasomes. Covaccination with cytE2A and GM-CSF or IL-2 DNA resulted in equivalent anti-tumor activity as E2. However, anti-ErbB-2 Ab was induced by E2 or E2A, but not cytE2 or cytE2A. Therefore, cytE2A appears to induce anti-tumor immunity without an Ab response. ErbB-2-specific CTL were detected in mice immunized with cytE2A and GM-CSF and have rejected tumor challenge. Depletion of CD8, but not CD4 T cells reduced anti-tumor immunity, indicating CTL as the effector cells. Covaccination with E2A and cytE2A induced synergistic anti-tumor activity, supporting enhanced peptide presentation from cytE2A, which was further evidenced by superior CTL activation using APCs expressing cytE2 vs E2. Taken together, cytoplasmic ErbB-2 DNA induced anti-tumor CTL, but not humoral response, demonstrating the feasibility of eliciting individual effector mechanism by targeted DNA vaccine.

Venezuelan Equine Encephalitis Replicon Immunization Overcomes Intrinsic Tolerance and Elicits Effective Anti-tumor Immunity to the ‘Self’ tumor-associated antigen, neu in a Rat Mammary Tumor Model

“…These results were obtained in a rat tumor model that has expression of the TAA in an entirely physiologic manner in contrast to the various rat neu transgenic mouse models [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57] and using a designed TAA target antigen selected to enhance both specificity and elicited Th1/ cytotoxic T lymphocyte (CTL) immune responses. The failure of immunization with VRPs expressing an irrelevant antigen, HA, to protect animals from tumor challenge strongly supports the generation of antigen-specific anti-tumor immune responses.…”

“…In contrast, the highly conserved rat homologue rat neu, both wild type and mutated/activated (tumorigenic) sequences, has been well characterized. Transgenic mouse models using both wild type and activated rat neu have been developed and have been useful in studies of anti-tumor immunotherapies including those targeting neu [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57]. It is widely acknowledged that expression of transgene encoded products can result in immunologic tolerance [47] however, the expression pattern is not always consistent with normal physiology.…”

HER-2/neu-gene engineered dendritic cell vaccine stimulates stronger HER-2/neu-specific immune responses compared to DNA vaccination

“…11,35 More recently, it has also been reported that the antitumor immunity derived from vaccination of DNA encoding ICD of HER-2/neu was mediated by HER-2/neu-specific CTL, but not humoral response. 36,37 Conceptually, vaccination with DNA en- Previous reports have shown that AdV transfection itself can mature DCs. 38,39 In this study, our data also showed that the transfected DC neu upregulated the expression of immunologically important molecules (MHC class II, CD40, CD54 and CD86) and inflammatory cytokines (IL-6, TNF-a, IL-1b, macrophage inflammatory protein-beta (MIP-b) and IP-10), compared with the untransfected DCs, indicating that AdV-transfected DCs are more immunogenic form of DCs with high immunostimulatory properties and capability in stimulating both natural killer cells and CTL.…”

Anti-HER2 vaccines: new prospects for breast cancer therapy

“…On the other hand, immunization of mice with another construct, pcytE2 (i.e., HER2 without signal peptide), elicited only a CD8 ? TL response [27]. These first pre-clinical studies used DNA vaccines alone injected intramuscularly (im).…”

“…Since effective vaccine strategies must circumvent tolerance, methods of breaking tolerance, such as presenting the critical epitope in a different molecular environment to the tolerized host, have been developed. Indeed, from the beginning, several studies have focused on evaluating whether tolerance to HER-2/neu could be circumvented by immunization with either peptide-based vaccines [22][23][24] or DNA [25][26][27]. Today, protein-, peptide-, DNA-and antiidiotype (Id) antibody-based vaccines have been developed with great specificity and without toxicity [28,29].…”