Shigella Sonnei 53G Challenge

Inclusion Criteria:

1. Male or non-pregnant female between 18 and 49 years of age (inclusive).

2. General good health defined as (a) no significant medical illness, (b) no clinically
significant physical examination findings and (c) no screening laboratory values
significantly outside the normal limits of the testing laboratory within 45 days of
challenge.

3. Demonstrate comprehension of the protocol procedures and knowledge of study by passing
a written examination (pass grade ≥70%) on day -1.

4. Willing to sign an informed consent form (ICF).

5. Willingness to participate for an inpatient stay lasting up to 11 days and an
outpatient follow-up lasting 6 months from challenge.

6. Willing to not smoke during the inpatient stay.

7. Available for all planned follow-up visits.

8. Negative serum pregnancy test at screening and negative urine pregnancy test on the
day of admission to the inpatient phase for female subjects of childbearing potential.
Females of childbearing potential must agree to use an effective method of birth
control (birth control pills, injection hormonal contraceptive, implant hormonal
contraceptive,

hormonal patch, IUD, sterilization by hysterectomy or tubal ligation, spermicidal
products and barrier methods such as cervical sponge, diaphragm, or condom) within two
months of challenge and during the entire study. Abstinence is acceptable. A woman is
eligible if she is monogamous with a vasectomized partner.

9. Willing to not donate blood for up to 6 months after completion of the inpatient phase
of the study.

10. Willing to refrain from participation in another investigational vaccine or drug trial
at least until after completion of the 6 month follow-up safety call.

Exclusion Criteria:

1. Presence of a significant medical condition (e.g. psychiatric conditions, alcohol or
illicit drug abuse/dependency, or gastrointestinal disease, such as peptic ulcer,
symptoms or evidence of active gastritis or gastroesophageal reflux disease,
inflammatory bowel disease), or other laboratory abnormalities which in the opinion of
the investigator precludes participation in the study.

2. Immunosuppressive illness or IgA deficiency

3. Positive serology results for HIV, HBsAg, HCV, or RPR (syphilis) antibodies.

4. Evidence of inflammatory arthritis on exam and/or HLA-B27 positive.

5. Family history of inflammatory arthritis.

6. Significant abnormalities in screening lab hematology or serum chemistry, as
determined by PI.

7. Allergy to fluoroquinolones or trimethoprim-sulfamethoxazole

8. Fewer than 3 stools per week or more than 3 stools per day as the usual frequency.

9. History of diarrhea in the 2 weeks prior to planned inpatient phase

10. Use of antibiotics during the 7 days before receiving the challenge inoculum dosing

11. Use of prescription and/or OTC medications that contain Imodium, acetaminophen,
aspirin, ibuprofen, and other non-steroidal anti-inflammatory drugs, during the 48
hours prior to investigational product administration

12. Travel within two years prior to dosing to countries where Shigella infection is
endemic.

13. Use of any medication known to affect the immune function [e.g., oral steroids,
parenteral steroids, or high-dose inhaled steroids (>800 μg/day of beclomethasone
dipropionate or equivalent and others): nasal and topical steroids are allowed] within
30 days preceding receipt of the challenge inoculum or planned use during the active
study period.

14. Serologic evidence of Shigella sonnei (titer > 1:2500)

15. A positive urine test for opiates.

16. A chronic disease (such as hypertension, hyperlipidemia or anxiety/depression) for
which doses of prescription medications are not stable for at least the past 3 months.

17. Scheduled and/or long-term use of oral steroids, parenteral steroids, or high-dose
inhaled steroids (>800 μg/day of beclomethasone dipropionate or equivalent) within the
preceding 6 months (Nasal, intra-articular, and topical steroids are allowed)

18. Have immunocompromised household contacts.

19. A clinically significant abnormality on physical examination, including a systolic
blood pressure >140 mm Hg or diastolic blood pressure >90 mm Hg, or a resting pulse
>100 beats/min or <55 beats/min (<50 beats/min for conditioned athletes).

20. Pregnant, nursing, or plan to become pregnant within 6 months of receipt of the study
product.

21. In the 4 weeks following challenge, subject will be living with or having daily
contact with elderly persons aged 70 years or more, diapered individuals, persons with
disabilities, children <2 years old, or a woman known to be pregnant or nursing, or
anyone with diminished immunity. This includes contact at home, school, day-care,
nursing homes, or similar places.

22. Work in a health care setting, day care center, or as a food handler in the 4 weeks
following the challenge with S. sonnei.

23. Use of any investigational drug or any investigational vaccine within 60 days
preceding challenge, or planned use during the 6 months after receipt of the study
agent.

24. Have received a licensed, live vaccine within 28 days or a licensed inactivated
vaccine within 14 days of receiving the challenge inoculum.

25. Inability to comply with inpatient rules and regulations.

26. Has any other condition that, in the opinion of the Investigator, would jeopardize the
safety or rights of a participant or would render the subject unable to comply with
the protocol.

27. Received blood or blood products within the past six months.