Comparison of adjuvants with Leishmania antigens in a guinea pig model to induce delayed-type hypersensitivity responses.

Background and purpose: Guinea pigs have been a traditional model for studies of delayed-type hypersensitivity. They are the natural host of Leishmania enriettii and have been experimentally infected with other species of Leishmania. They have been used as a skin-test model to screen potential antigens for use in diagnostic tests for Leishmania. Use of complete Freund's adjuvant (CFA), along with whole promastigote Leishmania antigen, was necessary to sensitize guinea pigs to invoke a sufficient cell-mediated immune response. However, use of CFA has come under scrutiny by Animal Care and Use Committees due to the pathologic changes associated with its use.

Methods: Thirty-two specific-pathogen-free male Hartley guinea pigs were inoculated with Leishmania antigens alone or mixed with one of three adjuvants (CFA, TiterMax, and liposomes), and were skin tested 2 weeks later.

Results: For the Leishmania antigens tested, guinea pigs that received liposomes as an adjuvant had skin-test responses comparable to those of guinea pigs that received CFA. TiterMax was also tested, but cellular responses at antigen test sites were poor.

Conclusions: Liposomes can be used in this model as a safe, effective adjuvant.