Interleukin-2 as a Co-Adjuvant for Liposomal Tetanus Toxoid

Abstract

Interleukin-2 (EL-2) plays a central role in cellular events associated with immune responses (Smith, 1988). For instance, it promotes the growth and proliferation of antigen-activated T cells (Carding et al, 1991) as well as the generation of effector T cells which include helper (Lederer et al, 1994), suppressor (Taylor et al, 1991) and cytotoxic T cells (Reiter and Rappaport, 1993). The latter cells secrete additional lymphokines which influence cells of the B cell (Brooks and Vitetta, 1986) and macrophage (Malkovski et al, 1987) lineages. In this respect, work with vaccines against Herpes simplex virus (HSV) (Weinberg and Merigan, 1988) and Haemophilus pleuropneumoniae (Anderson et al, 1987) suggests that IL-2 may act as an immunological adjuvant augmenting immune response to specific immunogens. This could be advantageous with populations of vaccinees such as haemodialysis patients who fail to respond to the alum-adsorbed hepatitis B vaccine. Indeed, such patients have been shown (Meuer et al, 1989) to produce antibodies against the hepatitis B surface antigen when the vaccine is administered together with IL-2, the latter acting as a co-adjuvant. Unfortunately, however, IL-2 as such in the amounts used can lead to toxicity (Anderson et al, 1992). Moreover, its pharmacokinetics may not be optimal in terms of eo-adjuvanticity.