Induction of HER2 Immunity in Outbred Domestic Cats by DNA Electrovaccination

Abstract

Domestic cats share human living environments and genetic traits. They develop spontaneous feline mammary carcinoma (FMC) with histopathology similar to human breast cancer. HER2 and AKT phosphorylation was demonstrated in primary FMC by immunoblot, indicating HER2 as a therapeutic target. FMC lines K12 and K248 expressing HER1, HER2 and HER3 were sensitive to receptor tyrosine kinase (RTK) inhibitors gefitinib and lapatinib. To test HER2 vaccine response in cats, purpose-bred, healthy cats were electrovaccinated with heterologous (xenogeneic) or point-mutated feline HER2 DNA. T-cell reactivity to feline self-HER2 was detected in 4 of 10 cats that received bear HER2, human/rat fusion HER2 (E2Neu) or mutant feline HER2 (feHER2-K) which contains a single amino acid substitution. The variable T-cell responses may resemble that in the genetically heterogeneous human population. All immune sera to heterologous HER2 recognized feline HER2 expressed in 3T3 cells (3T3/HER2), but not that in FMC K12 or K248. Immune sera to mutant pfeHER2-K bound 3T3/HER2 cells weakly, but they demonstrated better recognition of K12 and K248 cells that also express HER1 and HER3, suggesting distinct HER2 epitopes displayed by FMC that may be simulated by feHER2-K. In summary, HER2 DNA electroporation overcomes T-cell immune tolerance in ~40% healthy cats and induces antibodies with distinct specificity. Vaccination studies in domestic cats can expedite vaccine iteration to guide human vaccine design and better predict outcome, with the added benefit of helping feline mammary tumor patients.

Evolution of animal models in cancer vaccine development

“…Disease progression and histopathology of FMC are similar to that of human breast cancer [51;53–60]. FMC express EGFR, HER2 and HER3 as we reported with two feline mammary tumor lines K12 [61] and K248 [62] as well as primary tumor tissue [63]. ERBB family receptors are functional in these cell lines, as evident from the receptor tyrosine kinase inhibitors (TKI) gefitinib and lapatinib reducing proliferation in vitro and HER2 and AKT phosphorylation detected in primary tumor samples by Western blot.…”

“…Cats received DNA electroporation using the NEPA21 electroporator (Nepa Gene, Co.) as in mice. Vigorous antibody and T-cell responses to the heterologous human HER2 antigen were robust, with specific antibody titers exceeding 1,000,000 and T-cell response evident in all immunized cats [63]. These positive results provide the first evidence that DNA electrovaccination is feasible and effective in cats with consistent immunological response.…”

“…This conclusion was put to test in a “First in cats” immunization study [63]. Two heterologous vaccines, p bear HER2 (95% identity to feline HER2) and pE2Neu (human and rat fusion, 89% identity) were tested in parallel.…”

“…In another vaccine design, a feline HER2 variant (p fe HER2-K) was constructed with a single a.a. substitution Q141K in extracellular subdomain 1, a region often recognized by immune sera [12][63]. Protein modeling analysis (Sybyl-X Suite; Tripos) indicated that Q141K substitution introduced a novel positive charge onto an exposed surface region.…”

Trial watch: DNA-based vaccines for oncological indications

“…98 Additional studies on DNAbased vaccines specific for ERBB2 have been conducted in a model of feline mammary carcinoma (FMC), [123][124][125] which naturally reproduces several aspects of human breast cancer. 126 In particular, Gibson et al (from Wayne State University, Detroit, MI, USA) vaccinated healthy cats with a plasmid coding for heterologous (xenogeneic) or mutated feline ERBB2, demonstrating that vaccination can break immune tolerance and induce antibodies with distinct specificity. 126 Fibroblast activation protein alpha (FAP) is a serine peptidase integral to the plasma membrane and overexpressed by cancer-associated fibroblasts (CAFs).…”