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8 The Use of Flt3 Ligand as an Adjuvant for Hepatitis B Vaccination of Healthy Adults
T. G. Evans*1, M. Hasan2, L. Galibert3, and D. Caron3
1Univ. of California, Davis, USA; 2Univ. of Rochester, NY, USA; and 3Immunex Corp., Seattle, WA, USA
A phase I/II clinical trial was carried out to determine the safety of Flt3 ligand used as a vaccine adjuvant when administered to healthy human volunteers on 2 different schedules. In the first phase of this study, Flt3 ligand was administered SQ at a dose of 20 mug/kg (to a maximum of 1,500 mug) every day (n = 10) or every other day (n = 10) for 1 week. The Flt3 ligand injection series was followed 1 day later by the first of 3 vaccinations with the licensed hepatitis B vaccine given I.M. on a 0-, 1-, and 6-month schedule. Hepatitis B antibody titers were measured 4 weeks after the first and second vaccination and 3 weeks after the third immunization. In the second phase of the trial, 30 volunteers received either Flt3 ligand or placebo on the alternate day schedule in a randomized, double-blind design. The hepatitis B vaccine series was again administered the day after the last injection. The Flt3 ligand injections were safe and very well tolerated. The number of lineage negative (CD3(, CD14(, CD16(, CD19(, CD20(, CD56(), HLA-DRhi, CD11c+, and CD123( dendritic cells (DC) increased 23-fold, and the lineage negative, HLA-DRhi, CD11c(, and CD123bright pre-DCs increased 6-fold. There was an associated increase in monocytes and WBCs in the Flt3 ligand recipients. Despite the marked increase in peripheral circulating dendritic cells, no increase was observed in the hepatitis B antibody titers induced after vaccination.
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