HMGB1 mediates HAdV-7 infection-induced pulmonary inflammation in mice

Human adenovirus (HAdV) is a common respiratory pathogen in children, with no safe and effective treatment currently available. HAdV type 7 (HAdV-7), in particular, causes severe pediatric pneumonia with a high incidence of sequelae and mortality. Clinical data and animal experiments suggest that HAdV-7-induced pneumonia promotes cell necrosis, releasing a large number of inflammatory mediators. In recent years, the high mobility group box-1 (HMGB1) protein, released by necrotic cells, has been shown to play important roles in several viral infections. Here, we show that HMGB1 levels gradually increased in the media supernatants of HAdV-7 infected A549 cells, starting at 12 h post-infection. In vivo, HMGB1 levels in BALF and mRNA levels in lung tissues significantly increased after 3 days of HAdV-7 infection. Among the HMGB1 receptor genes, TLR-4 and TLR-9 expression increased, and so did the receptor for advanced glycation end-products (RAGE). Interestingly, NF-κB levels also increased concomitantly. Conversely, when HMGB1 was blocked, the pathological scores from lung tissues, inflammatory mediator levels, and viral copy number all were reduced significantly; in addition, HMGB1-related signaling pathway molecules, namely TLR-4, TLR-9, RAGE, and NF-κB were also reduced. We conclude that HMGB1 promotes HAdV-7 replication and signals through TLR-4, TLR-9, and RAGE receptors to activate NF-κB, stimulating the release of inflammatory mediators and contributing to adenoviral pathology. Thus, HMGB1 could be used as a therapeutic target in HAdV-7 infection.