Non-typeable Haemophilus influenzae protects human airway epithelial cells from a subsequent respiratory syncytial virus challenge

- Exposure of human epithelial cells to non-typeable Haemophilus influenzae (NTHi) inhibits a subsequent infection with RSV.
- NTHi-mediated protection requires live bacteria capable of invading the epithelia cell.
- NTHi-mediated inhibition was specific to RSV and failed to inhibit the replication of a subsequent influenza virus infection.

Respiratory syncytial virus (RSV) and the common commensal and opportunistic pathogen, non-typeable Haemophilus influenzae (NTHi) both serve as a frequent cause of respiratory infection in children. Although it is well established that some respiratory viruses can increase host susceptibility to secondary bacterial infections, few studies have examined how commensal bacteria could influence a secondary viral response. Here, we examined the impact of NTHi exposure on a subsequent RSV infection of human bronchial epithelial cells (16HBE14o-). Co-culture of 16HBE14o- cells with NTHi resulted in inhibition of viral gene expression following RSV infection. 16HBE14o- cells co-cultured with heat-killed NTHi failed to protect against an RSV infection, indicating that protection requires live bacteria. However, NTHi did not inhibit influenza A virus replication, indicating that NTHi-mediated protection was RSV-specific. Our data demonstrates that prior exposure to a commensal bacterium such as NTHi can elicit protection against a subsequent RSV infection.