CRISPR Screening Platform Uncovers 17 Host Genes Essential for Influenza A Infection

Influenza A virus (IAV) remains a leading pathogen responsible for seasonal flu epidemics and global pandemics. Upon entering a host cell, the virus relies heavily on an array of host cell proteins to complete its replication cycle—spanning viral attachment, endocytosis, nuclear uncoating, transcription, replication, assembly, and budding. These host proteins, "hijacked" by the virus, are known as host factors. Theoretically, targeting host factors could provide a broad-spectrum antiviral effect while minimizing the risk of inducing viral drug resistance.

In virological research, functionally validating host factors within intact animal models has always been a major bottleneck. Although a vast number of in vitro studies, such as siRNA screens in cell lines, have identified numerous host proteins potentially involved in viral replication, translating these findings into a deeper understanding of the viral infection cycle and pathogenic mechanisms has frequently been stalled by the lack of convenient and reliable in vivo verification methods.

To overcome this challenge, an international research team engineered a systematic in vivo screening platform specifically tailored for Influenza A virus research. This platform features a library composed of 84 distinct mouse strains generated via CRISPR-Cas9 gene-editing technology, targeting a candidate list of host genes derived from scientific literature and previous in vitro siRNA screens.

Utilizing this resource, the research team successfully identified 17 host genes whose knockout conferred significant resistance to Influenza A virus infection in mice. Further mechanistic exploration of two specific genes—Arhgef28 (encoding the protein RGNEF) and Lasp1—revealed that they protect the host through completely distinct pathways:

1. RGNEF Deficiency: Directly reduces viral load by inhibiting viral replication in the lungs, thereby mitigating pathological damage.
2. Lasp1 Modification: Enhances host resistance via a pathway independent of viral replication, likely involving the regulation of immune responses or tissue repair.

Figure 1. A systematic in vivo screening platform for influenza A virus. (Ueki H, et al., 2026)

Traditional studies on host factors rely predominantly on in vitro cultured cell lines, which fail to mirror the complex environment of a whole organism, such as immune system responses, tissue barriers, and metabolic states. The advent of CRISPR-Cas9 technology enables scientists to directly knock out specific genes in live animals and observe the subsequent impact on viral infection, dramatically increasing the reliability and translational potential of screening results.

In summary, by establishing an in vivo screening platform of 84 CRISPR-knockout mouse strains, this novel study successfully discovered 17 host genes capable of defending against Influenza A virus infection. Among them, RGNEF functions by suppressing viral replication, whereas LASP1 protects the host through a replication-independent mechanism. This research not only uncovers promising new targets for anti-influenza drug development but also provides a systematic in vivo methodology for the broader field of virology. It holds profound significance for understanding virus-host interactions and preparing for future pandemics. Furthermore, the research team's commitment to openly sharing this mouse library is poised to accelerate the pace of global influenza research.