['influenza']
['vis410', 'placebo']

        Inclusion Criteria:

          1. Male or female subjects of age 18-45 years, inclusive, at the time of informed
             consent.

          2. Women should fulfill one of the following criteria:

               -  Post-menopausal; either amenorrhea ≥ 12 months or follicle stimulating hormone >
                  40 mIU/mL.

               -  Surgically sterile; bilateral oophorectomy, hysterectomy, or tubal ligation.

               -  Women of childbearing potential participating in heterosexual sexual relations
                  must be willing to use adequate contraception until the end of the study.

               -  Must be sexually inactive by abstinence which is consistent with the preferred
                  and usual lifestyle of the subject.

          3. Women of childbearing potential must have a negative pregnancy test at screening
             (serum) and on Day -2 (urine).

          4. Non-vasectomized (or vasectomized less than 6 months prior to dosing) male subjects
             must use an effective birth control method (see Inclusion Criterion 2).

          5. Seronegative for the challenge virus (HAI ≤ 10).

        Exclusion Criteria:

          1. Known or suspected intolerance or hypersensitivity to the investigational study drug
             or virus.

          2. Has an acute or chronic medical condition that would render the investigational study
             drug unsafe or would interfere with the evaluation of the responses.

          3. Subjects receiving medications that affect the immune system.

          4. Significant adulthood history of seasonal hay fever or a seasonal allergic rhinitis or
             perennial allergic rhinitis or chronic or nasal or sinus condition.

          5. Subjects who have received any vaccination within the last 3 months or influenza
             vaccine within the last 6 months.

          6. Subjects with a confirmed diagnosis of influenza A within the last 6 months prior to
             screening.

          7. Subjects with abnormal nasal structure (including septal deviation and nasal polyps),
             chronic sinusitis, or reason (i.e., intolerance) that complicates nasopharyngeal
             swabbing.

          8. Presence of lung disease, asthma, or chronic obstructive pulmonary disease.

          9. Has a history of alcohol or drug abuse.

         10. A positive HIV antibody screen, HBsAg, HBcAb or hepatitis C antibody screen.

         11. Cancer or treatment for cancer, within 3 years, excluding basal cell carcinoma of the
             skin, which is allowed.

         12. Presence of immunosuppression or any medical condition that may be associated with
             impaired immune responsiveness.

         13. Anticipated presence of a household contact with potential immunosuppression.

         14. History of Guillain-Barré syndrome.

         15. Current professional activity as a healthcare worker who will return to work within 2
             weeks following challenge.

         16. Anticipated presence of a pregnant household contact, within 2 weeks following
             challenge.

         17. Women who are pregnant or breast-feeding, or consider becoming pregnant.

         18. Acute disease within 2 weeks prior to challenge.

         19. Elevated white blood cell count above 10.90 x 109/L or an absolute neutrophil count
             above 7.5 x 109/L.

         20. Current enrollment in any other investigational drug study or disease study or
             participation in an investigational drug study.

         21. Any other reasons for which the investigator considers the subject unfit for the
             study.
      