Introduction

Osteosarcoma is an aggressive primary mesenchymal tumor of bone in both humans and dogs. Unfortunately, local and systemic treatment strategies have resulted in limited improvements in survival times, and thus alternative approaches are needed. Immunotherapy is a possible approach as osteosarcoma is known to be highly immunogenic, spurring research into therapeutic vaccine strategies. This study evaluated the safety of the lyophilized canine osteosarcoma vaccine, live Listeria vector (COV-LLV).

Methods

Participating clinicians from 11 sites completed electronic data capture forms on dogs receiving the COV-LLV during and after vaccine administration.

Results

Forty-nine cases receiving 123 doses were included for analysis. Adverse events during COV-LLV administration were typically mild and self-limiting, most commonly nausea, lethargy, and fever (veterinary cooperative oncology group—common terminology criteria for adverse events grade 1). Four dogs (8%) cultured positive for Listeria (3 infections: an amputation site abscess, a septic stifle joint, and bacterial cystitis; and one patient whose lungs cultured positive on necropsy within 24 hours of COV-LLV administration). These cases join the previously reported Listeria-positive thoracic abscess that developed at a metastatic site in a canine following administration of COV-LLV. As concurrent treatment regimens varied, evaluation of the impact of COV-LLV on overall survival time was not possible.

Conclusion

Although side effects during administration of COV-LLV were generally mild and self-limiting, clinically significant Listeria infections are possible. In addition, as Listeria is zoonotic and patients with Listeria infections may shed the bacterium; caution for veterinarians and family members of dogs receiving attenuated therapeutic vaccinations is warranted.

Funding Information

None.