Abstract

Introduction: Bacterial extracellular vesicles (bEV) transport diverse cargoes, including nucleic acids, and play a crucial role during host-microbe interactions, including modifying host immune response. Neutrophil activation is prevalent in aortic disease pathogenesis, but the cause is unclear. The baseline neutrophilic bEV content and its dynamics are unknown and may provide insight into neutrophil activation in aortic disease. Research Question: Does open aortic surgery change neutrophil bEV content? Methods: Blood was collected pre and post-operatively from 6 patients undergoing open aortic surgery. Neutrophils were isolated using standard centrifugation techniques, and nucleic acids were purified. The V1-V3 16s rRNA segments were amplified with universal primers and sequenced using an Illumina MiSeq platform. Reads were processed in QIIME2 and aligned to reference banks of known bacterial sequences. Sequence abundance was analyzed with Kruskal-Wallis and Wilcoxon-rank tests. Results: The average patient age was 60.2 years, with 4 male patients and 4 current smokers. The most common phylum and genus represented in the neutrophil bacterial reads were Proteobacteria (Figure 1A) and Delftia , respectively. The relative abundance of Proteobacteria sequences increased overtime (p=0.042) from a median of 45.43% (IQR:35.3-52.0) to 70.8% (IQR:66.1-81.5, p=0.026) post-operatively, to 83.5% (IQR:60.7-89.7, p=0.004) on POD1 (Figure 1B). POD3 Proteobacteria sequence abundance was stable from POD1 at 81.4% (IQR:64.2-89.6). Conclusions: Neutrophils of patients with aortic disease rapidly change their bacterial sequence content in response to open aortic surgery. Bacteria in the phylum Proteobacteria change most dramatically and equilibrate between POD 1 and 3. Further studies will elucidate the impact changing bacterial sequence abundance and bEV content has on neutrophil activity and its relationship to disease pathogenesis.