• The A/Texas-like H3N2 Influenza challenge virus safely induced MMID in healthy volunteers, but was less effective than the A(H1N1)pdm09 challenge virus.

• This lower MMID rate of 40% was observed at the 107 TCID50 dose and was driven by less detection of shedding as the incidence of symptoms was similar to A(H1N1)pdm09.

• The limited serum antibody responses observed demonstrate that preexisting immunity in healthy volunteers against the seasonal H3N2 lineage may limit shedding compared to the more recently emerged seasonal A(H1N1)pdm09 lineage.

• The successful characterization of this H3N2 model makes future studies using this model to evaluate vaccine candidates possible.

Figure 4. HAI and NAI titers after H3N2 challenge. A) Overall there was an increase in HAI titer by Week 8 compared to Day 0 (pre-inoculation). B) NAI titers were elevated prior to inoculation and remained elevated throughout the study period. C) Participants with a response after challenge had a fourfold or greater increase in HAI titer after challenge and showed a significant rise by Week 8. D) A subset of participants did not have a rise in HAI titer after challenge and HAI titers remained low. Dotted lines indicate the lowest level of detection. Dashed lines indicate the level of protection (> 1:40)

Table 3. Percent of participants with influenza symptoms for both Influenza A H3N2 and H1N11 by viral shedding status. The 5 most common symptoms are bolded.

Figure 3. Proportion of participants with viral shedding by dose groups and symptom severity. A) Participants receiving 104 and 105 TCID50 did not have any viral shedding. Participants receiving 106 and 107 TCID50 had the highest proportion of shedding 1 day after challenge and no shedding by Day 7. B) The peak of symptom severity by FLU-PRO occurred on Day 4 with the most severe symptoms being reported on Days 2-4. C) The number of symptoms by day ranged from 0-12 with the average number of symptoms peaking on Day 3. D) FLU-PRO total scores and number of symptoms had similar trajectories. Circles represent means and the error bars represent standard error of the mean (SEM).

H3N2 H1N1

Viral shedding

(n=16)

No viral shedding

(n=21)

All (n=37)

Viral shedding

(n=20)

No viral shedding

(n=26)

All (n=46)

Arthralgia 1 (6.3%) 0 1 (2.7%) 2 (10.0%) 2 (7.7%) 4 (8.7%)

Chills 1 (6.3%) 0 1 (2.7%) 6 (30.0%) 1 (3.8%) 7 (15.2%)

Red/Watery Eyes 1 (6.3%) 0 1 (2.7%) 5 (25.0%) 2 (7.7%) 7 (15.2%)

Nasal/Sinus Congestion 7 (43.8%) 11 (52.4%) 18 (48.6%) 15 (75.0%) 9 (34.6%) 24 (52.2%)

Diarrhea 3 (18.8%) 1 (4.8%) 4 (10.8%) 1 (5.0%) 1 (3.8%) 2 (4.3%)

Dry Cough 2 (12.5%) 4 (19.0%) 6 (16.2%) 7 (35.0%) 6 (23.1%) 13 (28.3%)

Dyspnea on exertion 0 0 0 6 (30.0% 4 (15.4%) 10 (21.7%)

Fatigue 7 (43.8%) 7 (33.3%) 14 (37.8%) 12 (60.0%) 7 (26.9%) 19 (41.3%)

Fever (>38°C) 0 1 (4.8%) 1 (2.7%) 2 (10.0%) 1 (3.8%) 3 (6.5%)

Headache 8 (50%) 6 (28.6%) 14 (37.8%) 12 (60.0% 8 (30.8%) 20 (43.5%)

Myalgia 4 (25%) 0 4 (10.8%) 9 (45.0%) 3 (11.5%) 12 (26.1%)

Nausea 3 (18.8%) 1 (4.8%) 4 (10.8%) 3 (15.0%) 2 (7.7%) 5 (10.9%)

Productive Cough 1 (6.3%) 1 (4.8%) 2 (5.4%) 3 (15.0%) 1 (3.8%) 4 (8.7%)

Rhinorrhea 5 (31.3%) 4 (19.0%) 9 (24.3%) 15 (75.0%) 5 (19.2%) 20 (43.5%)

Sore Throat 8 (50%) 4 (19.0%) 12 (32.4%) 13 (65.0%) 7 (26.9%) 20 (43.5%)

Sweats 2 (12.5%) 0 2 (5.4%) 6 (30.0%) 2 (7.7%) 8 (17.4%)

Table 1. Clinical outcomes of participants receiving Influenza A H3N2.

Table 2. Clinical outcomes of participants receiving Influenza A H1N11.

Notes: Mild to moderate influenza disease (MMID) is defined as positive molecular testing AND at least 1 symptom. Data are presented as No. (%). Abbreviations: TCID50, tissue culture infectious dose; MMID, mild to moderate influenza disease.

Figure 2. Disease severity measures by days of shedding and symptoms and by number of symptoms after H3N2 challenge. A) There was no viral shedding in the lowest dose groups. The median duration was 1 day in the two highest dose groups. B) Participants in all dose groups experienced influenza symptoms with a median duration of 5 days for all participants. C) The highest number of symptoms occurred among the highest dose group with a median of 3.5 symptoms over the study period. Blue lines represent medians with error bars representing interquartile ranges (IQR).

• Healthy volunteer influenza challenge studies provide an opportunity to better understand influenza pathogenesis and correlates of protection.

• The development of currently available vaccines and therapeutics have relied on these studies as will future universal vaccine candidates.

• Expanding the repertoire of influenza challenge viruses are needed to test the cross-reactivity and broad protection of universal vaccine candidates.

• To characterize a wild-type influenza A/Texas-like H3N2 challenge virus in healthy volunteers.

• To compare this H3N2 challenge virus to a previously validated wild-type Influenza A(H1N1)pdm09 human infection model.1

▸ Healthy volunteers were isolated at the NIH Clinical Center for < 9 days. ▸ Participants received a single dose of a reverse genetics, cell-based, GMP-

manufactured, wild-type A H3N2 virus intranasally. ▸ Dose escalation was performed from 104 to 107 TCID50. ▸ Viral shedding and clinical disease were evaluated daily, including clinician

assessments and a validated patient-reported outcome tool, FLU-PRO.2-3

Figure 1. Study Enrollment

BACKGROUND

METHODS

RESULTS

CONCLUSIONS

REFERENCES

Validation of a Wild-Type Influenza A/Texas-like H3N2 Human Challenge Model with Comparison to the Validated A(H1N1)pdm09 Model

H3N2 Total Symptoms Shedding MMID

104 TCID50 4 4 (100%) 0 0

105 TCID50 4 2 (50%) 0 0

106 TCID50 9 6 (67%) 5 (56%) 4 (44%)

107 TCID50 20 15 (75%) 11 (55%) 8 (40%)

Total 37 27 (73%) 16 (43%) 12 (32%)

H1N1 Total Symptoms Shedding MMID

103 TCID50 5 2 (40%) 0 0

104 TCID50 4 2 (50%) 0 0

105 TCID50 5 4 (80%) 1 (20%) 1 (20%)

106 TCID50 19 17 (89%) 9 (47%) 9 (47%)

107 TCID50 13 11 (85%) 10 (77%) 9 (69%)

Total 46 36 (78%) 20 (43%) 19 (41%)

Enrolled (n=49)

Inoculated (n=41)

Included in Analysis(n=37)

104 TCID50

(n=4)

105 TCID50

(n=4)

106 TCID50

(n=9)

107 TCID50

(n=20)

Co-infection with another respiratory

virus (n=4)

Abnormal Echo or PFT (n=2)

Respiratory infection (n=2)

Voluntary withdrawal

(n=1)

Positive drug test (n=2)

Did not meet eligibility criteria

(n=1)

Dose groups

Contact: Alison Han, MD, MSAddress: 33 North Drive MS 3203, Bethesda, MD 20892Email: alison.han@nih.govPhone: 301-480-5722 Fax: 301-480-4509

Alison Han, MD, MS, Lindsay M. Czajkowski, MSN, NP-C, Amanda Donaldson, BSN, Holly Ann Baus, RN, MSN, Susan M. Reed, BA, CRC, Rani S. Athota, PhD, Tyler Bristol, BS, Luz Angela Rosas, MS, MLS(ASCP)CM, Adriana Cervantes-Medina, BS, Jeffery K. Taubenberger, MD, PhD, Matthew J. Memoli, MD, MS

LID Clinical Studies Unit, Viral Pathogenesis and Evolution Section, Laboratory of Infectious Diseases, NIAID, National Institutes of Health, Bethesda, MD

1. Memoli, M. J., et al. (2016). "Evaluation of Antihemagglutinin and Antineuraminidase Antibodies as Correlates of Protection in an Influenza A/H1N1 Virus Healthy Human Challenge Model." MBio 7(2).

2. Powers, J. H., et al. (2016). "Development of the Flu-PRO: a patient-reported outcome (PRO) instrument to evaluate symptoms of influenza." BMC Infect Dis 16(1): 1.

3. Powers, J. H., et al. (2018). "Reliability, Validity, and Responsiveness of InFLUenza Patient-Reported Outcome (FLU-PRO(c)) Scores in Influenza-Positive Patients." Value Health 21(2): 210-218.

OBJECTIVES

Funding: This research was supported by the Intramural Research Program of the NIH, NIAID.