EFFECT OF MTP-PE LIPOSOMES AND INTERLEUKIN-7 ON INDUCTION OF ANTIBODYAND CELL-MEDIATED IMMUNE-RESPONSES TO A RECOMBINANT HIV-ENVELOPE PROTEIN

We investigated the ability of human recombinant interleukin-7 (IL-7) to enhance the immune responses of mice vaccinated with either the alu m-associated or liposome-formulated recombinant human immunodeficiency virus (HIV)-envelope protein, env-2-3(SF2) (a nonglycosylated denatur ed gp 120 of HIV-1(SF2) produced in genetically engineered yeast). Pat hogen-free (C3H) mice were vaccinated on days 0, 14, and 28 with 10 mu g of either the alum-associated env-2-3(SF2) or liposome-formulated e nv-2-3(SF2), both containing a lipophylic muramyl tripeptide, MTP-PE. Liposome-formulated IL-7 (5 mu g/mouse) or empty liposomes were given on days 7, 14, 21, and 28. Antibody response against the immunized ant igen, evaluated on day 21 and day 35 or 42, showed that liposome-formu lated antigen induced higher antibody titer than did alum-associated a ntigen, and these antibody responses can be enhanced by concurrent adm inistration of IL-7 liposomes. Spleen cells were harvested on day 21 a nd day 35 or 42 to evaluate cytotoxic T lymphocyte responses directed against autologous cells infected with vaccinia virus-expressing HIV-e nvelope protein. Mice treated with liposome-formulated antigen express ed the highest cytotoxic t-lymphocyte (CTL) activity, regardless of wh ether IL-7 liposome was given as an immune potentiator. In contrast, s pleen cells from mice vaccinated with alum-associated antigen exhibite d minimal CTL response, which was enhanced by concurrent IL-7 liposome treatment. Collectively, IL-7 liposome treatment enhanced the antibod y production of the alum-associated or liposome-formulated env-2-3(SF2 ), whereas its enhancement of CTL activity was detected only in mice v accinated with alum-associated antigen.