Adenovirus phagocytosis by neutrophils triggers a pro-inflammatory response

Adenoviruses are common pathogens that have been engineered and used for medical purposes. Their recognition by innate immune cells such as macrophages and dendritic cells has been widely studied, but very little information is available on adenovirus interaction with neutrophils. Using cytometry and confocal and electron microscopy, we showed that neutrophils bind to antibody-coated adenoviruses and engulf them in a phagosome. Using a single-cell transcriptomic approach, we found that adenovirus phagocytosis activates a specific transcriptional program in neutrophils. It also triggers calcium entry into neutrophils, reactive oxygen species production in the phagosome, and CXCL8 release. Moreover, 4 hours after adenovirus incubation, 50% of neutrophils undergo calcium- and RIPK3-dependent cell death, accompanied by Neutrophil Extracellular Trap emission. Because of this rapid cell death, engulfed adenoviruses are not fully degraded after 3 hours, and the remaining viruses are still capable of expressing their genome in target cells. Thus, our data suggest that, during adenoviral infection, the neutrophil response may promote a pro-inflammatory environment that could damage host tissues. Author SummaryAdenoviruses are common viruses that trigger mild infections, although they can lead to more severe diseases such as gastroenteritis or respiratory tract infections in immunocompromised patients. Non-replicative adenovirus-derived vectors are widely used in medicine for vaccination and antitumor therapy. In this study, we investigated how adenoviruses affect neutrophils, the first immune cells recruited to the site of infection and crucial players in the immune system. We used various methods to explore this interaction. We found that adenoviruses bind to neutrophils, and that this binding is enhanced by human serum containing antibodies against the viruses. This binding is followed by adenovirus internalization, and we showed that it triggers several responses. These responses include the activation of specific genes, the entry of calcium into the cells, the production of reactive oxygen species (molecules that fight infections), and the release of signaling molecules to attract other immune cells. However, this process also leads to rapid neutrophil death and the release of structures called Neutrophil Extracellular Traps. Because of this quick death, adenoviruses are not fully broken down and can still infect other cells. We suggest that this neutrophil response might create an inflammatory environment that could potentially harm the bodys tissues.