These studies were undertaken with the approval of the Institutional Biosafety Committee (Protocol# #01/08-2010-1) and the Institutional Animal Care and Use (IACUC) Committee (Protocol # 0904028). Five to six week old female Balb/c mice (Harlan Laboratories) were housed in microisolater cage for 4 days in the Animal Resource Center at the University of Texas Medical Branch before beginning the immunization protocol. Mice in groups of five were immunized by subcutaneous inoculation of four different concentrations of VLPs (1.75, 3.5, 7 or 14 mg/ mouse, referred to subsequently as treatment groups A through D respectively) prepared just prior to use in sterile endotoxin free PBS. No adjuvant was used. A group of five mice inoculated with sterile endotoxin free PBS served as negative control group. Mice in the four treatment groups (A through D) were boosted (6 mg/ mouse) on days 15 and 29; the negative control group received PBS. Blood was collected from the submandibular vein of the animals on days 21, 14, 21, 28 and 35; they were euthanized on day 35.