The Immunological Co-Adjuvant Action of Liposomal Interleukin-15
It is well known that the immunological adjuvant property of liposomes established in the early 70’s (Gregoriadis, 1990) can be further enhanced by interleukin-2 (IL-2) (Tan and Gregoriadis, 1989; Ho et al, 1992; Abraham and Shah, 1992; Sencer et al, 1991; Mbawuike et al, 1990; Anderson et al, 1994; Gursel and Gregoriadis, 1997a). It has been suggested (Meuer et al, 1989) that the co-adjuvant activity of liposomal IL-2 could prove useful in the vaccination of certain individuals who are low or non-responders (eg. immunosuppressed patients). Such findings with liposomal IL-2 have raised the question as to whether the recently discovered (Grabstein et al, 1994) interleukin-15 (IL-15) exhibits a similar action: IL-15 interacts with components of the IL-2 receptor and, as with IL-2, promotes T cell growth (Giri et al, 1994; Matthews et al, 1995; Carson et al, 1994), serves as a chemoattractant for human blood T-cells (Wilkinson and Liew, 1995) and induces B-cell proliferation and differentiation in the presence of stimuli (Armitage et al, 1995). Here we have studied IL-15 behaviour in vivo by entrapping the cytokine together with a model antigen (tetanus toxoid) into liposomes in a variety of formulations and monitoring its co-adjuvant activity in mice. Data indicate that IL-15 augments immune responses against the toxoid to levels well above those achieved with liposomal toxoid alone, but only when both the cytokine and the antigen are associated with the same vesicles.
KeywordsTetanus Toxoid Small Unilamellar Vesicle Covalent Coupling Liposomal Surface Empty Liposome
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