Trancriptome profiling of murine lung after pneumococcal respiratory infection, antibiotic administation, and treatment with immunostimulants

The study aimed at defining the transcriptional responses of the respiratory tract after respiratory infection with Streptococcus pneumoniae, treatment with antibiotic and administration of immunostimulatory molecules. For this purpose, mice were infected by intranasal route with S. pneumoniae. After 12h, animals were treated by orogastric administration of amoxicillin and either intraperitoneal injection of monophosphoryl lipid A or intranasal instillation of flagellin FliC∆174-400. Whole lungs were then sampled at selected times for microarray analyses. Animals were maintained in individually ventilated cages and handled in a vertical laminar flow cabinet (class II A2, ESCO, Hatboro, PA). Experiments complied with current national, institutional and European regulations and ethical guidelines (Animal facility agreement C59-350009, Institut Pasteur de Lille; Protocol 2015121722429127). Six-to-eight weeks old female BALB/cJRj mice were used for all in vivo experiments. Mice were first anesthetized by intraperitoneal injection of 1.25 mg ketamine plus 0.25 mg xylazine in 250 μl PBS, then infected intranasally with 30µL of a PBS suspension containing 2-4106 S. pneumoniae serotype 1 (clinical isolate E1586). All treatments described were administered 12h post-infection. Amoxicillin trihydrate (AMX) was prepared in a stock solution of 1.75 mg/mL in sterile water, then adjusted to a final dose of 10µg/mouse before intragastric administration by oral gavage at a volume of 200µL. Monophosphoryl lipid A (MPLA) from S. minnesota R595 (Re) (Innaxon UK) in sterile distilled water at a concentration of 1 mg/L was adjusted to the dose of 50µg in sterile PBS and administered by intraperitoneal injection at a volume of 200µL. Alternatively, the recombinant flagellins FliC∆174-400 (2.5 µg in 30 μl PBS) or PBS alone were administrated intranasally under light anesthesia by inhalation of isoflurane. Mock animals received only amoxicillin.