Advances in cancer vaccine development are facilitated by animal models reflecting key features of human
cancer and its interface with host immunity. Several series of transplantable preneoplastic and neoplastic
mouse mammary lesions have been used to delineate mechanisms of anti-tumor immunity. Mimicking
immune tolerance to tumor-associated antigens (TAA) such as HER2/neu, transgenic mice developing
spontaneous mammary tumors are strong model systems for pre-clinical vaccine testing. In these models, HER2 DNA vaccines are easily administered, well-tolerated, and induce both humoral and cellular
immunity. Although engineered mouse strains have advanced cancer immunotherapy, basic shortcomings remain. For example, multiple mouse strains have to be tested to recapitulate genetic regulation
of immune tolerance in humans. Outbred domestic felines more closely parallel humans in the natural
development of HER2 positive breast cancer and their varying genetic background. Electrovaccination
with heterologous HER2 DNA induces robust adaptive immune responses in cats. Importantly, homologous feline HER2 DNA with a single amino acid substitution elicits unique antibodies to feline mammary
tumor cells, unlocking a new vaccine principle. As an alternative approach to targeted vaccination, nonsurgical tumor ablation such as cryoablation induces anti-tumor immunity via in situ immunization,
particularly when combined with toll-like receptor (TLR) agonist. As strategies for vaccination advance,
non-invasive monitoring ofhost response becomes imperative. As an example, magnetic resonance imaging (MRI) and positron emission tomography (PET) scanning following administration of tryptophan
metabolism tracer [11C]-alpha-methyl-tryptophan (AMT) provides non-invasive imaging of both tumor
growth and metabolic activities. Because AMT is a substrate of indoleamine-pyrrole 2,3-dioxygenase
(IDO), an enzyme that produces the immune regulatory molecule kynurenine, AMT imaging can provide
novel insight of host response. In conclusion, new feline models improve the predictive power of cancer
immunotherapy and real-time PET imaging enables mechanistic monitoring of host immunity. Strategic
utilization of these new tools will expedite cancer vaccine development.