This study is a randomized, placebo-controlled, dose-escalation, single-center study evaluating two different doses of Imprime PGG, each in 7 different dosing regimes. A total of 66 subjects will be enrolled into 2 cohorts and, within each cohort, randomized to 1 of 7 treatment groups receiving Imprime PGG or placebo in varied dosing regimens with granulocyte-colony stimulating factor (G-CSF).