Characterization of host responses during Pseudomonas aeruginosa acute lung infection in the lungs and blood and after treatment with the synthetic immunomodulatory peptide IDR-1002

Pseudomonas aeruginosa is an opportunistic pathogen that causes nosocomial pneumonia and infects patients with cystic fibrosis. P. aeruginosa lung infections are difficult to treat due to bacterial resistance to antibiotics, and strains with multi-drug resistance are becoming more prevalent. Here we examined the use of a small host defense peptide, innate defense regulator 1002 (IDR-1002), in an acute P. aeruginosa lung infection in vivo. IDR-1002 significantly reduced the bacterial burden in the bronchoalveolar lavage fluid (BALF) as well as MCP-1 in the BALF and serum, KC in the serum, and IL-6 in the BALF. RNA-Seq was conducted on lungs and whole blood and the effects of P. aeruginosa, IDR-1002, or the combination of P. aeruginosa and IDR-1002 were evaluated. Differential gene expression analysis showed that P. aeruginosa increased multiple inflammatory and innate immune pathways as well as affected hemostasis, matrix metalloproteinases, collagen biosynthesis, and various metabolism pathways in the lungs and/or blood. Infected mice treated with IDR-1002 had significant changes in gene expression compared to untreated infected mice, with fewer differentially expressed genes associated with the inflammatory and innate immune responses to microbial infection, and treatment also affected morphogenesis, certain metabolic pathways, and lymphocyte activation. Overall, these results show that IDR-1002 was effective in treating P. aeruginosa acute lung infections and associated inflammation. RNA-Seq profiling of mouse lung tissue or whole blood, with 4 conditions (negative control, IDR-1002 control, PA103 infected, and IDR-1002 treated PA103 infected), with 3-5 replicates per condition.