Influenza A virus suppresses SARS-CoV-2 replication during co-infection

In a recent study posted on bioRxiv* In a preprint server, researchers will study the interaction of influenza A virus with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in co-infected hosts and these using human respiratory epithelial cultures. Examine virus-host interactions. Simultaneously exposed host.

study: Counterintuitive effects of antiviral therapy on influenza A-SARS-CoV-2 co-infection due to viral interferenceImage credit: Artbox / Shutterstock.com

Background

The epidemic of novel SARS-CoV-2 variants, the recent resurgence of influenza A viruses, and the winter seasonality of the two viruses raise the possibility of co-infection. Co-infection is thought to exacerbate infection of one or both viruses, but research suggests that viral interference, which occurs when one virus slows the replication rate of the other virus, is also possible. I’m here.

Induction of the interferon (FIN) response, an antiviral defense mechanism induced by respiratory viruses that can suppress the replication of other viruses, has been hypothesized to be one mechanism by which viral interference occurs.

Viral genome replication triggers IFN responses in airway epithelia. IFN-stimulated genes (ISGs) are expressed when cytosolic innate immune sensors sense viral ribonucleic acid (RNA).

Because the expression of ISGs is triggered by viral load Antiviral drugs are available against both viruses and the interaction between co-infection and antiviral therapy needs further investigation.

About research

In the present study, researchers used air-liquid interface cultures of human airway epithelial cells to study virus-virus interactions and response dynamics between host and virus. In addition, the impact of the influenza antiviral drug oseltamivir during co-infection with influenza A and SARS-CoV-2 was also examined.

Human bronchial epithelial cells were ethically obtained from healthy donors for airway epithelial culture. Mature and differentiated epithelial cells were confirmed based on the presence of active cilia and mucus production during viral infection.

in vitro Infection was performed by inoculating cultured bronchial epithelial cells for 1 h, resulting in the lowest multiplicity of infection (MOI) for each virus required for exponential and reproducible replication.

Oseltamivir treatment was initiated at 16, 40, and 64 hours after vaccination. Cell cultures were examined at 72 hours to assess host response and viral load. Additionally, RNA from each differentiated epithelial cell well was isolated and subjected to a reverse transcription-polymerase chain reaction (RT-PCR) assay.

RT-PCR was performed to determine the levels of influenza A virus RNA as well as the messenger RNA (mRNA) of ISG, the SARS-CoV-2 nucleocapsid gene, and the housekeeping gene hypoxanthine-guanine phosphoribosyltransferase (HPRT). Quantified.

Investigation result

Infection with influenza A 3 days before SARS-CoV-2 infection suppressed SARS-CoV-2 replication more than 10,000-fold 72 hours after inoculation. Co-infection with influenza A virus and SARS-CoV-2 also significantly suppressed SARS-CoV-2 replication. Interestingly, prior or concurrent SARS-CoV-2 co-infection did not suppress influenza A virus replication.

Expression of ISGs was elevated 72 hours after SARS-CoV-2 infection with simultaneous and consecutive co-infections with influenza A virus and infection with influenza A virus alone. Thus, co-infection with influenza A virus induces stronger IFN responses, enhances antiviral responses during co-infection with SARS-CoV-2, and suppresses SARS-CoV-2 replication.

Effect of previous or concurrent influenza A virus (IAV) infection on SARS-CoV-2 replication. (A) Experimental design of simultaneous or sequential infections in differentiated human airway epithelial cultures. (B) Quantification of SARS-CoV-2 RNA by RT-qPCR on day 1 (24 h after CoV-2 infection; white bars) and day 3 (72 h; gray bars), which is below the limit of detection. Expressed as fold change. (C, D) mRNA levels of interferon-stimulated genes ISG15 or MX1 ​​by RT-qPCR. Housekeeping gene HPRT. The graph combines the results of his two independent experiments using primary human bronchial epithelial cultures from different healthy adult donors, with 4–5 replicates for each condition. . Mean, and His SEM of 9-10 replicates are shown. Mann-Whitney p-values ​​are provided for conditions significantly different from SARS-CoV-2 infection on day 3 only.

Since no viral inhibition of SARS-CoV-2 against influenza A was observed, the effect of oseltamivir, an influenza A antiviral agent that inhibits viral replication, was investigated. To this end, treatment with oseltamivir reduced influenza A viral load during single influenza A infections and co-infections with SARS-CoV-2.

Oseltamivir treatment did not affect SARS-CoV-2 viral load in SARS-CoV-2 infection alone, but oseltamivir treatment improved SARS-CoV-2 replication during co-infection with influenza A . Her ISG is expressed in host tissues only when administered at her 16 hours rather than 40 hours post-infection.

Conclusion

In the current study, human bronchial epithelial cell cultures were used to investigate the interaction between viruses and the dynamics of co-infection with influenza A virus and SARS-CoV-2.

Overall, the results suggest that influenza A virus triggers ISG expression and suppresses SARS-CoV-2 replication during influenza A and SARS-CoV-2 co-infection. Conversely, SARS-CoV-2 does not suppress influenza A replication in simultaneous or sequential co-infections.

Experiments with the influenza A antiviral drug oseltamivir showed that treatment with oseltamivir rescued SARS-CoV-2 replication during co-infection, supporting a clear diagnosis of co-infection and appropriate antiviral therapy. The importance of use was emphasized.

*Important Notices

Bio Rxiv We publish a non-peer-reviewed, preliminary scientific report and should not be taken as conclusive, to guide clinical practice/health-related actions, or to be treated as established information.