Influenza D Virus, Secondary Bacterial Infections, and the Immune Response—Oh My!

Influenza D virus (IDV) was identified in 2011 and is the most recently added genus of the Orthomyxoviridae family of viruses. Although cattle are known to be a natural reservoir for IDV, there is limited knowledge about host immune responses against IDV or how IDV may contribute to secondary bacterial infection susceptibility. This project utilized in vivo and in vitro experiments to evaluate host responses against both primary IDV infection and secondary Staphylococcus aureus (S. aureus) infection. Following primary IDV and secondary S. aureus infection, mice did not exhibit clinical symptoms normally associated with secondary bacterial infections. In fact, primary IDV infection led to improved weight loss, survival, and recovery in mice compared to S. aureus infection alone, suggesting IDV provides a protective effect to the host against secondary S. aureus infection. When investigating early immune responses in human alveolar epithelial cells following IDV infection, an increase in interferon-β was observed. This project provides evidence for the first time that primary IDV infection may protect the host against subsequent bacterial infections, as demonstrated through the anti-viral immune responses observed in mouse and lung epithelial cell models