(494) Investing the Role of IFI35 on Cell Viability Following Bacterial and Viral Infection by means of a Novel Human IFI35 Knock Out Respiratory Cell Line

Introduction/Rationale: Viral infections, such as Respiratory Syncytial Virus (RSV) or SARS-CoV-2, can trigger a widespread antiviral immune response that are both protective and pathogenic. Patients with respiratory viral infections are often susceptible to secondary bacterial infections, which may lead to further complications. One agent of particular concern according to the World Health Organization, is the gram-negative bacteria Acinetobacter baumannii, which has a proclivity for infecting ventilator-assisted patients. Interferon-induced protein 35 (IFI35) is upregulated during the antiviral interferon response and may modulate the host immune response, however, the specific impact and mechanisms by which IFI35 acts during viral and bacterial infections remains unclear. We sought to investigate the effect of IFI35 on lung epithelial cell viability under viral and bacterial infection conditions.

Methods: IFI35 knockout cells were generated via CRISPR-Cas9 in a human lung epithelial cell line, A549. We transfected wild-type and novel IFI35 knock out (IFI35KO) A549 cells with poly I:C, a mimic of viral RNA, to simulate a viral infection in the absence of viral proteins that may alter the natural host immune response. An MTT assay was then used to quantify cell viability. Additionally, control and IFI35KO cells were infected with A. baumannii at a MOI of 25 and host cell viability was assayed via AnnexinV/7-AAD at 8 and 24 hours post infection.

Results: IFI35KO was confirmed at the DNA and protein level in two independent cell lines. Following both viral and bacterial infection conditions, IFI35KO cells displayed increased cell viability relative to wild-type A549s.

Conclusion: These findings suggest that IFI35 plays a role in cell death during both viral and bacterial host immune responses. Further study of IFI35’s role cell dealth pathways may assist in developing new interventions to prevent complications of severe viral infections or reduce the risk of secondary infection, ultimately improving patient outcomes.