TDENV-PIV Dosage: 0.5 mL of DENV serotypes 1-4 (4 µg / serotype) in alum adjuvant Mode of administration: intramuscular (IM) into the subject's upper arm, deltoid area of the subject's arm; vaccination will be given in the non-dominant arm whenever possible TDENV-LAV F17 Dosage: 0.5 mL of the post-transfection LAV F17 vaccine Mode of administration: subcutaneously into the upper-outer triceps/deltoid area of the subject's arm; vaccination will be given in the non-dominant arm whenever possible Schedule Varied, 2 vaccinations per volunteer in a heterologous prime-boost strategy. First dose on Day 0 (PIV) AND a second dose (LAV) on Day 180 for group 1. First dose on Day 0 (PIV) AND a second dose (LAV) on Day 90 for group 2.