Transcutaneous immunization of domestic animals: opportunities and challenges.

Transcutaneous immunization (TCI), the topical application of antigen and adjuvant directly onto intact skin, can safely and effectively elicit systemic immune responses in mice and humans against a variety of antigens. This novel method of vaccine delivery has the potential to provide a safe and convenient method by which vaccines may be delivered to elicit protective immunity in domestic animals. To date, however, immune responses induced by TCI in companion and production animals has not been reported. In this report, we demonstrate that TCI may be widely applicable to many animals. Immune responses elicited by TCI require further optimization for each antigen and species, and success may depend upon the structure and composition of the skin of the target species. The prospect of TCI as a practical and broadly applicable approach to vaccination in veterinary medicine is discussed in the context of these challenges.