Dose Escalating Study of a Prototype CS6 Subunit Vaccine With a Modified Heat-labile Enterotoxin From Enterotoxigenic Escherichia Coli (ETEC)

This is an open-label, Phase 1 clinical trial in which a total of 50 subjects will receive
three injections of either CssBA alone, dmLT alone or CssBA + dmLT. The vaccine will be
administered via IM injection to alternating deltoid regions on days 0, 21 and 42. Each
subject will receive the same dose at each vaccination dependent upon group assignment. Group
A is considered a pilot group in which all 3 doses will be administered and subjects
monitored for safety 7 days after the third vaccination, prior to the enrollment of subjects
in Group B.

Inclusion Criteria:

1. Healthy, adult, male or female, age 18 to 45 years (inclusive) at the time of
enrollment.

2. Completion and review of comprehension test (achieved > 70% accuracy).

3. Signed informed consent document.

4. Available for the required follow-up period and scheduled clinic visits.

5. Women: Negative pregnancy test with understanding (through informed consent process)
to not become pregnant during the study or within three (3) months following last
vaccination.

Exclusion Criteria:

1. Health problems (for example, intercurrent febrile illness, chronic medical conditions
such as psychiatric conditions, diabetes mellitus, hypertension or any other condition
that might place the subject at increased risk of adverse events) - study clinicians,
in consultation with the PI, will use clinical judgment on a case-by-case basis to
assess safety risks under this criterion. The PI will consult with the Research
Monitor as appropriate.

2. Clinically significant abnormalities on physical examination.

3. Immunosuppressive drugs (use of systemic corticosteroids or chemotherapeutics that may
influence antibody development) or illness (including IgA deficiency, defined by serum
IgA <7mg/dL).

4. Women who are pregnant or planning to become pregnant during the study period plus
three (3) months beyond the last received dose and currently nursing women.

5. Participation in research involving another investigational product (defined as
receipt of investigational product or exposure to invasive investigational device) 30
days before planned date of first vaccination or anytime through the last study safety
visit.

6. Positive blood test for HBsAg, HCV, HIV-1/2.

7. Clinically significant abnormalities on basic laboratory screening.

8. Exclusionary skin disease history/findings that would confound assessment or prevent
appropriate local monitoring of AEs, or possibly increase the risk of a local AE

9. History of chronic skin disease (clinician judgement)

10. Acute skin infection/eruptions on the upper arms including fungal infections, severe
acne or active contact dermatitis

11. Allergies that may increase the risk of AEs

12. Regular use (weekly or more often) of antidiarrheal, anti-constipation, or antacid
therapy

13. Abnormal stool pattern (fewer than 3 stools per week or more than 3 stools per day) on
a regular basis; loose or liquid stools on other than an occasional basis

14. History of microbiologically confirmed ETEC or cholera infection in the last 3 years

15. Travel to countries where ETEC or V. cholerae or other enteric infections are endemic
(most of the developing world) within 3 years prior to dosing (clinician judgement)

16. Symptoms consistent with Travelers' Diarrhea or concurrent with travel to countries
where ETEC infection is endemic (most of the developing world) within 3 years prior to
dosing, OR planned travel to endemic countries during the length of the study

17. Vaccination for or ingestion of ETEC, cholera, or E. coli heat labile toxin within 3
years prior to dosing

18. Occupation involving handling of ETEC or V. cholerae currently, or in the past 3 years