Vaccine, Vol. 15. No. 16, pp. 1753-1760, 1997 Q 1997 Elsevier Science Ltd. All rights reserved Printed in Great Britain zyxwvuts PII: SO264-410X(97)00111-4 0264-410X/97 $17+0.00 ELSEVIER zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Effect of IL-4 and IL-12 liposomal formulations on the induction of immune response to bovine herpesvirus type-l glycoprotein D M.E. Baca-Estrada*$, M. Foldvari’f, M. Snider*, S. van Drunen Littel-van den Hurk* and L.A. Babiuk” zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Activation of diflerent T-helper (Th) responses following immunisation has profound and specific influences on the development of the immune response and on the ability of a vaccine to confer protection. Since cytokines are capable of influencing the stimulation of distinct T-cell responses, their encapsulation in vaccines should modulate antigen-specific immune responses. Unfortunately, the use of cytokines in vivo is hampered by their rapid clearance and inactivation. One possible solution to this problem is the use of liposomes to entrap both cytokines and antigen. This approach will not only protect the cytokine but will also deliver the two components simultaneously to the same site. The authors examined, therefore, the immune responses elicited by systemic immunisation of mice with liposome formulations containing a truncated form of bovine herpesvirus type-l glycoprotein D (tgD) together with IL-4 or IL-12. Subcutaneous immunisation with liposomes containing tgD and IL-I2 signi~cant~ enhanced the induction of antigen-specific cellular and humoral immune responses. These responses were characterised by an increase in IFN-;< secreting cells and the induction of tgD-specific IgG2a antibodies. In contrast, encap- sulation of IL-4 into tgD-liposomes did not enhance the humoral immune response to gD but significantly influenced the development of antigen-specific IL-4 secreting cells. Our results indicated that encapsulation of IL-12 into the liposomes was necessary for the systemic adjuvant effect and demonstrated the feasibility of using liposome technology and cytokines to manipulate the development of diRerent antigen-specijic Th subsets in vivo. 0 1997 Elsevier Science Ltd. Keywords: IL-12 IL-d, liposomes The ability of IL-4 and IL-12 to influence resistance or susceptibility to infection has been shown in numerous systems (reviewed in’). IL-4 has been shown to have immunoregulatory activity favouring the generation of Th2 responses, whereas IL-12 enhances Thl develop- ment. This information is relevant in tailoring vaccines capable of inducing appropriate immune effector mechanisms and providing immunity at various anatomical sites. However, the use of cytokines in viva is hampered by their rapid clearance and inactivatior?. To overcome this problem, multiple injections of high doses of cytokines have been used’, increasing the risk “Veterinary Infectious Disease Organization, University of Saskatchewan, Saskatoon, Sask. S7N 5E3, Canada. GolIege of Pharmacy and Nutrition, University of Saskatchewan, Saskatoon, Sask. S7N 5E3, Canada. $To whom correspondence should be addressed. Tel.: (306) 966 7479; fax: (306) 966 7478. (Received 7 Novemeber 1996; revised version received 28 March 1997; accepted 3 April 1997) of side-effects and making this approach impractical for use as vaccine adjuvants. One possible solution is the use of liposomes to entrap both cytokines and antigens. This approach should not only protect the cytokine but also deliver the two components simulta- neously to the same site. In a number of models, it has been shown that liposome vaccine formulations of this nature are more efficient at inducing immunity than simple mixtures of antigen and cytokine alone’. In addition to their safety, liposomes have been shown to stimulate both humoral and cell-mediated immunity, including cytotoxic T lymphocyte (CTL) responses”. Liposomes also offer the advantages of low toxicity and biodegradability compared with more conventional adjuvants. Liposomes arc composed of bilayercd phospholipid membrane-forming vesicles enclosing, and surrounded by, an aqueous solution. Depending on the conditions used for production, liposomes can vary in form as well as in size. The two standard types of liposomes are Vaccine 1997 Volume 15 Number 16 1753