Utilizing Microbes to Treat Naturally Occurring Cancer in Veterinary Species

Purpose of Review Therapeutics that harness the immune system to exert their effect may be more critically tested in immunocompetent pet animals than mice or other model systems. This is because pet animals share their environment with humans and spontaneously develop complex, heterogeneous cancers that exhibit similar immunosuppressive microenvironment features. Furthermore, owners of companion animals are increasingly seeking more effective therapeutic options for their pets that go beyond traditional chemotherapy. Microbial-based anticancer therapeutics exploit evolutionarily acquired host-pathogen interactions to break host immune tolerance and/or induce tumor cell death. Therefore, this review summarizes recent studies evaluating microbial-based therapeutics for naturally occurring cancers in veterinary species. Recent Findings Adenovirus and poxvirus vectors and genetically modified bacteria expressing tumor-associated antigens are the basis of promising therapeutics targeting an array of canine and feline cancers. Several well-funded multi-institutional clinical trials are currently underway evaluating microbial-based therapeutics for naturally occurring veterinary cancers. Recent advancements in our ability to monitor immune responses in these species and a growing appreciation for the similarities and differences in host-pathogen interactions between humans and animals will assist in future comparative studies.