Validation of the wild-type influenza A human challenge model H1N1pdMIST: an A(H1N1)pdm09 dose-finding investigational new drug study

Abstract

Background: Healthy volunteer wild-type influenza challenge models offer a unique opportunity to evaluate multiple aspects of this important virus. Such studies have not been performed in the United States in more than a decade, limiting our capability to investigate this virus and develop countermeasures. We have completed the first ever wild-type influenza A challenge study under an Investigational New Drug application (IND). This dose-finding study will lead to further development of this model both for A(H1N1)pdm09 and other strains of influenza.

Methods: Volunteers were admitted to an isolation unit at the National Institutes of Health Clinical Center for a minimum of 9 days. A reverse genetics, cell-based, Good Manufacturing Practice (GMP)-produced, wild-type A(H1N1)pdm09 virus was administered intranasally. Escalating doses were given until a dose was reached that produced disease in a minimum of 60% of volunteers.

Results: An optimal dose of 10(7) tissue culture infectious dose 50 was reached that caused mild to moderate influenza disease in 69% of individuals with mean viral shedding for 4-5 days and significant rises in convalescent influenza antibody titers. Viral shedding preceded symptoms by 12-24 hours and terminated 2-3 days prior to symptom resolution, indicating that individuals may be infectious before symptom development. As expected, nasal congestion and rhinorrhea were most common, but interestingly, fever was observed in only 10% of individuals.

Conclusions: This study represents the first healthy volunteer influenza challenge model using a GMP-produced wild-type virus under an IND. This unique clinical research program will facilitate future studies of influenza pathogenesis, animal model validation, and the rapid, efficient, and cost-effective evaluation of efficacy of novel vaccines and therapeutics. Clinical Trials Registration.NCT01646138.

Keywords: H1N1; challenge; healthy volunteer; influenza; influenza A.

Published by Oxford University Press on behalf of the Infectious Diseases Society of America 2014. This work is written by (a) US Government employee(s) and is in the public domain in the US.

Figures

Figure 1.

Viral shedding and clinical illness. A, Timing of symptoms and viral shedding for each individual participant who tested positive for influenza A by multiplex respiratory testing during their inpatient stay. Shedding typically began within 24–48 hours of challenge (solid line), and symptoms typically began 24–48 hours after shedding but lasted longer (dashed line). One participant (number 20) shed virus for 3 days without manifestation of symptoms. B, Aggregate quantitation of viral shedding (solid line) and correlation to number of symptoms each day (dashed line) during the inpatient stay (± standard error of the mean [SEM]). C, Mean severity of illness as measured by overall disease clinical score (number of symptoms multiplied by overall duration of symptoms) by dose group and positive or negative influenza shedding during inpatient stay. D, Days of shedding at the 3 doses that produced participants with positive nasal washes (± interquartile range [IQR]). E, Days of symptoms in the top 3 doses of all participants regardless of positive or negative nasal influenza viral shedding (±IQR). Abbreviation: TCID50, tissue culture infectious dose 50.

Figure 1.

Viral shedding and clinical illness. A, Timing of symptoms and viral shedding for each individual participant who tested positive for influenza A by multiplex respiratory testing during their inpatient stay. Shedding typically began within 24–48 hours of challenge (solid line), and symptoms typically began 24–48 hours after shedding but lasted longer (dashed line). One participant (number 20) shed virus for 3 days without manifestation of symptoms. B, Aggregate quantitation of viral shedding (solid line) and correlation to number of symptoms each day (dashed line) during the inpatient stay (± standard error of the mean [SEM]). C, Mean severity of illness as measured by overall disease clinical score (number of symptoms multiplied by overall duration of symptoms) by dose group and positive or negative influenza shedding during inpatient stay. D, Days of shedding at the 3 doses that produced participants with positive nasal washes (± interquartile range [IQR]). E, Days of symptoms in the top 3 doses of all participants regardless of positive or negative nasal influenza viral shedding (±IQR). Abbreviation: TCID50, tissue culture infectious dose 50.

Figure 2.

Antibody response. Geometric mean titer (GMT) of all challenge participants at different time points of both hemagglutination inhibition (HAI; top) and neuraminidase inhibition titers (NAI; bottom) pre- and postchallenge in the 3 low-dose groups (combined) and each of the 2 high-dose groups (shown separately). Error bars represent 95% confidence intervals. No significant change in GMT was noted for either HAI or NAI at the lowest 3 doses, whereas statistically significant changes were seen at the 2 higher doses. Participants were enrolled if their screening HAI titer was ≤1:40, approximately 8 weeks prior to challenge. For 4 participants in the 106 and 107 tissue culture infectious dose 50 (TCID50) groups, day 0 titers were 1:80 or 1:160, suggesting influenza exposure between screening and challenge.

Figure 3.

Clinical score observed by baseline hemagglutination inhibition (HAI) and neuraminidase inhibition (NAI) titers (A and B, respectively). Mean clinical score (number of symptoms multiplied by overall duration of symptoms in days) of all participants (regardless of presence or absence of viral shedding) at different baseline HAI and NAI titers is shown (± standard error of the mean [SEM]). Overall, there was a trend, for both HAI and NAI independently, that those with a higher baseline titer had a shorter duration and smaller number of clinical symptoms.

Figure 4.

Cytokine response. Mean rise in interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), and granulocyte colony-stimulating factor (G-CSF) in all participants both pre- and postchallenge, separated by those who met criteria for mild to moderate influenza disease (MMID), and those who did not (± standard error of the mean [SEM]). Significance is noted by P value between MMID and no MMID by day.