Exploratory Study to Estimate the Prophylactic Efficacy of Palivizumab in Healthy Adult Participants Inoculated With RSV

Inclusion Criteria: 1. An informed consent document signed and dated by the participant and the Investigator. 2. Aged between 18 and 55 years old on the day of signing the consent form. 3. In good health with no history, or current evidence, of clinically significant medical conditions, and no clinically significant test abnormalities that will interfere with participant safety, as defined by medical history, physical examination, (including vital signs), Electrocardiogram (ECG), and routine laboratory tests as determined by the Investigator. 4. A documented medical history prior to enrolment. 5. The following criteria are applicable to female participants participating in the study. 1. Females of childbearing potential must have a negative pregnancy test prior to enrolment. 2. Females of non-childbearing potential: <!-- --> 1. Post- menopausal females; defined as having a history of amenorrhea for \>12 months with no alternative medical cause, and /or by Follicle stimulating hormone (FSH) level \>40mIU/mL, confirmed by laboratory 2. Documented status as being surgically sterile (e.g. tubal ligation, hysterectomy, bilateral salpingectomy and bilateral oophorectomy). 6. The following criteria apply to female and male participants: 1. Female participants of childbearing potential must use one form of highly effective contraception. Hormonal methods must be in place from at least 2 weeks prior to the first study visit. The contraception use must continue until 30 days after the date of viral challenge/last dosing with IMP (whichever occurs last). Highly effective contraception is as described below: <!-- --> 1. Established use of hormonal methods of contraception described below (for a minimum of 2 weeks prior to the first study visit). When hormonal methods of contraception are used, male partners are required to use a condom with a spermicide: 1\. Oral 2. Intravaginal 3. Transdermal b. Intrauterine device (IUD) c. Intrauterine hormone-releasing system (IUS) d. Bilateral tubal ligation e. Male sterilisation (with the appropriate post vasectomy documentation of the absence of sperm in the ejaculate) where the vasectomised male is the sole partner for that woman. f. True abstinence - sexual abstinence is considered a highly effective method only if defined as refraining from heterosexual intercourse during the entire period of risk associated with the study treatments. The reliability of sexual abstinence needs to be evaluated in relation to the duration of the clinical trial and the preferred and usual lifestyle of the participant. b) Male participants must agree to the contraceptive requirements below at entry to quarantine and continuing until 90 days after the date of Viral challenge / last dosing with the investigational medicinal product (IMP) (whichever occurs last): 1. Use a condom with a spermicide to prevent pregnancy in a female partner or to prevent exposure of any partner (male and female) to the IMP. 2. Male sterilisation with the appropriate post vasectomy documentation of the absence of sperm in the ejaculate (please note that the use of condom with spermicide will still be required to prevent partner exposure). This applies only to males participating in the study 3. In addition, for female partners of childbearing potential, that partner must use another form of contraception such as one of the highly effective methods mentioned above for female participants. 4. True abstinence - sexual abstinence is considered a highly effective method only if defined as refraining from heterosexual intercourse during the entire period of risk associated with the study treatments. The reliability of sexual abstinence needs to be evaluated in relation to the duration of the clinical trial and the preferred and usual lifestyle of the participant. c) In addition to the contraceptive requirements above, male participants must agree not to donate sperm following discharge from quarantine until 90 days after the date of Viral Challenge/last dosing with IMP (whichever occurs last). 7\. For Part 2 of the study: Sero-suitable to the challenge virus, as defined in the study Analytical Plan. Exclusion Criteria: Medical History 1. History of, or currently active, symptoms or signs suggestive of upper or lower respiratory tract infection within 4 weeks prior to the first study visit. 2. a) Any history or evidence of any other clinically significant or currently active systemic comorbidities including psychiatric disorders (includes participants with a history of depression and/or anxiety). b) And/or other major disease that, in the opinion of the Investigator, may put the participant at undue risk, or interfere with a participant completing the study and necessary investigations. The following conditions apply: • Participants with clinically mild atopic eczema/atopic dermatitis and clinically mild psoriasis may be included at the Investigator's discretion (e.g., if small amounts of regular topical steroids are used, no eczema in cubital fossa; moderate to large amounts of daily dermal corticosteroids is an exclusion). * Rhinitis (including hay fever) which is clinically active or history of moderate to severe rhinitis, or history of seasonal allergic rhinitis likely to be active at the time of inclusion into the study and/or requiring regular nasal corticosteroids on an at least weekly basis, within 30 days of admission to quarantine will be excluded. Participants with a history of currently inactive rhinitis (within the last 30 days) or mild rhinitis may be included at the PI's discretion. * Participants with a physician diagnosed underactive thyroid who have been controlled on treatment for at least 6 months with evidence of a normal thyroid function test (TFT) can be included at the discretion of the PI. * Any concurrent serious illness including history of malignancy that may interfere with the aims of the study or a participant completing the study. Basal cell carcinoma within 5 years of initial diagnosis or with evidence of recurrence is also an exclusion. o Participants with a history of psychiatric illness including depression and/or anxiety of any severity within the last 2 years can be included if the Patient Health Questionnaire (PHQ-9) and / or the Generalised Anxiety Disorder Questionnaire (GAD-7) is less than or equal to 4. Participants with a PHQ-9 or GAD-7 score of between 5 and 9 may be included following consultation with a Senior Physician (Clinical Lead for Screening) who may advise further consultation with the PI. o Participants reporting physician diagnosed migraine can be included provided there are no associated neurological symptoms such as hemiplegia or visual loss. Cluster headache/migraine or prophylactic treatment for migraine is an exclusion. * Participants with physician diagnosed mild Irritable Bowel Syndrome (IBS) not requiring regular treatment can be included at the discretion of the PI. 3. Participants who have smoked ≥ 10 pack years at any time \[10 pack years is equivalent to one pack of 20 cigarettes a day for 10 years\]). 4. A total body weight ≤ 50 kg and Body Mass Index (BMI) ≤18 kg/m2 and ≥30kg/m2 5. Females who: 1. Are breastfeeding, or 2. Have been pregnant within 6 months prior to the study. 6. History of anaphylaxis-and/or a history of severe allergic reaction or significant intolerance to any food or drug, as assessed by the PI. 7. Venous access deemed inadequate for the phlebotomy and cannulation demands of the study. 8. a) For Part 2 of the study: Any significant abnormality altering the anatomy of the nose in a substantial way or nasopharynx that may interfere with the aims of the study and in particular any of the nasal assessments or viral challenge, (historical nasal polyps can be included, but large nasal polyps causing current and significant symptoms and/or requiring regular treatments in the last month will be excluded). b) Any clinically significant history of epistaxis (large nosebleeds) within the last 3 months of the first study visit and/or history of being hospitalized due to epistaxis on any previous occasion. c) Any nasal or sinus surgery within 3 months of the first study visit. Prior or Concomitant Medications and Assessments 9. For Part 2 of the study: 1. Evidence of vaccinations within the 4 weeks prior to the planned date of viral challenge/first dosing with IMP (whichever occurs first). 2. Intention to receive any vaccination(s) before the last day of Follow-up. (NB. No travel restrictions will apply after the Day 28 (±3 days) Follow-up Visit). 10. Receipt of blood or blood products, or loss (including blood donations) of 470 mL or more of blood during the 3 months prior to the planned date of viral challenge/first dosing with IMP (whichever occurs first) or planned during the 3 months after the final visit. 11. a) Receipt of any investigational drug within 3 months prior to the planned date of viral challenge/first dosing with IMP (whichever occurs first). b) Receipt of three or more investigational drugs within the previous 12 months prior to the planned date of viral challenge/first dosing with IMP (whichever occurs first). For Part 2 of the study: c) Prior inoculation with a virus from the same virus-family as the challenge virus. d) Prior participation in another human viral challenge study with a respiratory virus in the preceding 3 months, taken from the date of viral challenge in the previous study to the date of expected viral challenge in this study 12. a) Confirmed positive test for drugs of abuse on first study visit. One repeat test allowed at PI discretion. b) History or presence of alcohol addiction, or excessive use of alcohol (weekly intake in excess of 28 units alcohol; 1 unit being a half glass of beer, a small glass of wine or a measure of spirits), or excessive consumption of xanthine containing substances (e.g. daily intake in excess of 5 cups of caffeinated drinks e.g. coffee, tea, cola). 13. For Part 2 of the study: A forced expiratory volume in 1 second (FEV1) \< 80%. 14. Positive human immunodeficiency virus (HIV), active hepatitis A (HAV), B (HBV), or C (HCV) test. Other 15. Those employed or immediate relatives of those employed at hVIVO or the Sponsor. 16. Any other finding that, in the opinion of the Investigator, deems the participant unsuitable for the study.