This study will provide preliminary safety and comparative immunogenicity data for the E.coli derived rPA vaccine administered by intramuscular (IM) injection at Day 0 and Month 1.Doses will range from 5 μg to 100 μg rPA, and at each dose-level, rPA will either be combined with phosphate-buffered saline (PBS) or adsorbed to Alhydrogel.

This is a safety study with an open-label part (2 groups), followed by a dose-ranging part evaluating safety and immunogenicity using a double-blind, sequential-group design with randomization and placebo-control within each of the 6 groups. Volunteers in each dose group will receive two IM injections at Day 0 and Month 1

Volunteers are eligible for this study if they meet all the following criteria:

• Citizens of the U.S.

• Age 18 to 40 years.

• For women, a negative serum pregnancy test will be required at study entry and within 24 hours prior to each vaccination, as well as verbal assurance that adequate birth control measures are applied prior to initial vaccination and for 3 months after the last vaccination.

• Good health as determined by medical history, physical examination, and clinical judgment.

• Normal Baseline Clinical Laboratory Values at screening including:

  • Complete Blood Count (CBC) including:
  • White Blood Cell Count: 3.8 -10.8
  • Red Blood Cell Count (Mill/MCL)
  • Male: 4.20 - 5.80
  • Female: 3.80 - 5.10
  • Hemoglobin (G/DL)
  • Male: 13.2 - 17.1
  • Female: 11.7 - 15.5
  • Hematocrit (%)
  • Male: 38.5- 50.0
  • Female: 35.0 - 45.0
  • Platelet Count: 140 - 440 (THOUS/MCL)
  • Differential
  • Urine dipstick for protein and blood: negative or trace. If either is ≥ 1+, obtain complete urinalysis (UA). If microscopic UA confirms evidence of hematuria or proteinuria ≥ 1+, the volunteer is ineligible.
  • Negative serology for HIV infection (ELISA test).
  • CPK within normal limits
  • Hepatic Function Tests including AST, ALT, ALK PHOS.
  • Total bilirubin, BUN, serum creatinine, serum electrolytes

• Availability for at least 13 months of follow-up from the time of the screening visit.

• Successful completion of the Test of Understanding defined as 90% correct with three opportunities to take test. Errors will be reviewed with volunteer after each test.

• Commitment for trial participation and signature of the approved consent form.