Development of an objective gene expression panel as an alternative to self-reported symptom scores in human influenza challenge trials

• Main Authors: Julius Muller, Eneida Parizotto, Richard Antrobus, James Francis, Campbell Bunce, Amanda Stranks, Marshall Nichols, Micah McClain, Adrian V. S. Hill, Adaikalavan Ramasamy, Sarah C. Gilbert
• Format: Article
• Language: English
• Published: BMC 2017-06-01
• Series: Journal of Translational Medicine
• Subjects: Influenza; Challenge trial; Symptom scores; Biomarker; Transcriptomics
• Online Access: http://link.springer.com/article/10.1186/s12967-017-1235-3

Abstract Background Influenza challenge trials are important for vaccine efficacy testing. Currently, disease severity is determined by self-reported scores to a list of symptoms which can be highly subjective. A more objective measure would allow for improved data analysis. Methods Twenty-one volunteers participated in an influenza challenge trial. We calculated the daily sum of scores (DSS) for a list of 16 influenza symptoms. Whole blood collected at baseline and 24, 48, 72 and 96 h post challenge was profiled on Illumina HT12v4 microarrays. Changes in gene expression most strongly correlated with DSS were selected to train a Random Forest model and tested on two independent test sets consisting of 41 individuals profiled on a different microarray platform and 33 volunteers assayed by qRT-PCR. Results 1456 probes are significantly associated with DSS at 1% false discovery rate. We selected 19 genes with the largest fold change to train a random forest model. We observed good concordance between predicted and actual scores in the first test set (r = 0.57; RMSE = −16.1%) with the greatest agreement achieved on samples collected approximately 72 h post challenge. Therefore, we assayed samples collected at baseline and 72 h post challenge in the second test set by qRT-PCR and observed good concordance (r = 0.81; RMSE = −36.1%). Conclusions We developed a 19-gene qRT-PCR panel to predict DSS, validated on two independent datasets. A transcriptomics based panel could provide a more objective measure of symptom scoring in future influenza challenge studies. Trial registration Samples were obtained from a clinical trial with the ClinicalTrials.gov Identifier: NCT02014870, first registered on December 5, 2013