NasoShield Study of Safety and Immunogenicity

This study is a Phase 1, randomized, double-blind, placebo-controlled, dose-escalation clinical trial to evaluate the safety and immunogenicity of NasoShield in healthy adults 18 to 49 years of age. Subjects will be screened within 28 days of randomization (Day 1). The study is comprised of 2 parts:

* Part A: Approximately 120 subjects who meet all inclusion and no exclusion criteria and provide written informed consent will be enrolled into 4 sequential cohorts of 30 subjects each defined by the NasoShield dose (1×108, 1×109, 1×1010, and 1×1011 vp). Within each cohort (and the sentinel group in the first dose cohort), subjects will be randomized in a 4:1:1 ratio to receive 1 intranasal dose of NasoShield (Day 1), 1 intranasal dose of placebo (Day 1), or 3 subcutaneous 0.5 mL doses of BioThrax 14 days apart (Days 1, 15, and 29). NasoShield and placebo will be administered in a double-blind fashion, and BioThrax will be administered in an open-label fashion. * Part B: Approximately 25 subjects who meet all inclusion and no exclusion criteria and provide written informed consent will be randomized in a 4:1 ratio to receive 2 intranasal doses of NasoShield at the highest well tolerated dose from Part A or placebo 21 days apart (Days 1 and 22). NasoShield and placebo will be administered in a double-blind fashion.

Subjects will return to the investigational site for multiple visits through Day 361. At each visit, the subject will be asked about the interim medical history and use of any medications, and safety and immunogenicity assessments will be performed.