Inflammation induced by influenza virus impairs innate control of human pneumococcal carriage

Simon P. Jochems; Fernando Marcon; Beatriz F. Carniel; Mark Holloway; Elena Mitsi; Emma Smith; Jenna F. Gritzfeld; Carla Solórzano; Jesús Reiné; Sherin Pojar; Elissavet Nikolaou; Esther L. German; Angie Hyder-Wright; Helen Hill; Caz Hales; Wouter A.A de Steenhuijsen Piters; Debby Bogaert; Hugh Adler; Seher Zaidi; Victoria Connor; Jamie Rylance; Helder I. Nakaya; Daniela M. Ferreira

Indeed, for subjects in the control group with very low carriage densities, which were only 145 detectable by molecular methods, no monocyte recruitment was observed (Fig S4c) . This suggests 146 that a minimum Spn load is required for sensing and monocyte recruitment and that LAIV infection 147 interferes with this process. While MCP-1 was not significantly induced following Spn carriage, 148 levels correlated with numbers of monocytes at all timepoints ( Fig S5a) . Furthermore, stratification 7 of individuals showed that those with increased MCP-1 levels at day 2 post Spn inoculation exhibit 150 increased monocyte recruitment (Fig S5b) . Levels of IL-6, IFN-γ and TNF-α also correlated with 151 levels of monocytes at each time point, but stratification of individuals did not reveal a differential 152 recruitment of monocytes (Fig S5a,b) . In a second, independent cohort that did not receive any 153 vaccine, monocytes were increased at day 9 following Spn inoculation, which correlated with 154 increased MCP-1 levels in nasal fluid, validating these results (Table S3 and Fig S5c) . pneumococcal cytokine responses by re-challenge was absent (Fig 4a and Fig S6a) . The 162 production of the above five cytokines correlated with decreased density at day 29 post Spn 163 inoculation, suggesting these responses are involved in Spn clearance (Fig 4b) . To test whether 164 monocytes/macrophages were the source of these cytokines we compared the cytokine signature 165 from whole nasal cells with that from alveolar macrophages exposed to Spn in vitro (Fig 4c) .