Correlations between initial cytokine/chemokine concentrations and clinical parameters at presentation (temperature, respiratory rate, oxygen saturation) and the clinical outcomes (hospital length-of-stay, ICU admission).

<p>For correlations with temperature, respiratory rate, oxygen saturation, and length-of-stay, the Spearman's rank coefficients (<i>rho</i>) were shown. For risk of ICU admission, the adjusted odds ratio and the 95% confidence interval (CI) per log₁₀ unit increase in cytokine concentration were shown (adjusted for age, comorbidity and time from onset). Data on respiratory rate was incomplete in seasonal influenza cases, and there were too few ICU admissions to allow meaningful analysis.</p><p>*p<0.05,</p><p>**p<0.01.</p

PBMC activation and <i>ex vivo</i> cytokine/chemokine expression during seasonal influenza infection.

<p>PBMC actively expressed IL-6, (CXCL8/IL-8), CCL2/MCP-1, CXCL10/IP-10, and CXCL9/MIG during acute influenza infection; upon illness recovery, cytokine production decreased, and there was a corresponding increase in cellular responsiveness to stimuli. Cytokine response pre-/post-stimulation and the trend changes in cytokine expression across time points (with PHA/LPS stimulation – red bars; without stimulation – blue bars; folds increase in expression or the ‘responsiveness’ – gray bars) were compared using the <i>Mann-Whitney U</i> test (asterisks, underlined), and the <i>Jonckheere-Terpstra</i> test (blue/gray triangles and asterisks), respectively. IL-17A did not appear to be activated via the PHA/LPS stimulation pathway.</p

Serial changes in plasma cytokine/chemokine concentrations during the course of hospitalization.

<p>There was sustained elevation of the proinflammatory cytokines (IL-6, CXCL8/IL-8, CCL2/MCP-1, sTNFR-1) in severe pH1N1 pneumonia; the adaptive-immunity related cytokines (CXCL10/IP-10, CXCL9/MIG, IL-17A) were markedly suppressed compared with seasonal influenza. All patients with pH1N1 influenza (severe pneumonia, n = 34; milder illness, n = 29) received antiviral treatment soon after hospitalization/recruitment; none had received high-dose corticosteroids or other immunosuppressants for ‘viral pneumonitis’ or ‘ARDS’<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026050#pone.0026050-Lee2" target="_blank">[8]</a>. Among seasonal influenza patients (most had complicated illnesses, see <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026050#pone-0026050-t001" target="_blank">Table 1</a> footnotes), 30(57%) received antiviral treatment. Median concentrations at each time point are shown for each group; the interquartile ranges (presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026050#pone-0026050-t001" target="_blank">Table 1</a>) are omitted here for clarity. Fewer mild pH1N1 and untreated seasonal influenza patients remained hospitalized at day 6–7 for study (Day 1, n = 116; Day 3–4, n = 62; Day 6–7, n = 30).</p

Plasma cytokine/chemokine concentrations in adults hospitalized for seasonal or pandemic H1N1 influenza, measured at presentation.

<p>Values are stated as median (interquartile range, IQR); pandemic influenza A/H1N1 ‘severe’: radiographic pneumonia plus hypoxemia; ‘mild’: hospitalized for significant respiratory or systemic symptoms (only 5/29 patients had mild pulmonary infiltrates on chest radiographs)<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026050#pone.0026050-Lee2" target="_blank">[8]</a>. Over 80% of seasonal influenza patients had respiratory/cardiovascular complications, and nearly half developed hypoxemia. Only 2 patients received long-term immunosuppressants in these cohorts. The normal plasma reference ranges of cytokines/chemokines were obtained from >100 healthy individuals <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026050#pone.0026050-Lee2" target="_blank">[8]</a>, <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0026050#pone.0026050-Lee4" target="_blank">[15]</a>.</p><p>Comparisons: (<b>1</b>) Seasonal influenza A (combined) vs influenza B; (<b>2</b>) seasonal influenza A/H3N2 vs A/H1N1; (<b>3</b>) severe pH1N1 vs all seasonal influenza cases (similar results when influenza B was excluded); (<b>4</b>) pH1N1 cases, ‘severe’ vs ‘mild’. Fewer pH1N1 infections had detectable levels of IFN-γ compared with seasonal influenza (8.8% vs 43.4%; p<0.001). Cytokine/chemokine concentrations were also compared between severe pH1N1 pneumonia and a subgroup of seasonal influenza patients with complicated infections and hypoxemia: CXCL10/IP-10, CXCL9/MIG and IL-17A concentrations were all significantly lower in severe pH1N1 infections (all p<0.01), and fewer had detectable IFN-γ level (p = 0.001). Complete data on plasma C-reactive protein (n = 34), serum amyloid A and cortisol were unavailable for pH1N1 cases. Mann-Whitney U test,</p><p>**p≤0.01,</p><p>*p<0.05;</p><p>#p<0.10.</p