Respiratory Virus-Specific and Time-Dependent Interference of Adenovirus Type 2, SARS-CoV-2 and Influenza Virus H1N1pdm09 During Viral Dual Co-Infection and Superinfection In Vitro

Background. Understanding how respiratory viruses interference could be important to highlights potential strategies to fight these human infecting agents. Aim. Investigate the possible interactions between Adenovirus Type 2 (AdV2), Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), and Influenza A/H1N1 pandemic (H1N1pdm09) using the A549 cell line. Methods. Single infections, co-infections and superinfections (at 3 h and 24 h after the first virus- infection) were performed varying the multiplicity of infection (MOI). Kinetics of virus replication and the mRNA expression of IFN-α, IL-1, and IL-6 were assessed using real-time qPCR. Results. Coinfection experiments showed different growth dynamics, depending on the presence of specific virus and time. AdV2 replication remained stable or possibly boosted in the presence of coinfection with each of the two RNA viruses used. SARS-CoV-2 replication was instead facilitated by H1N1pdm09 but hampered by AdV2, indicating different possible interactions. Finally, H1N1pdm09 replication was variably reduced in the presence of AdV2 and SARS-CoV-2. Superinfection experiments showed that replication of all viruses was affected by the time and MOI. The mRNA expression of IFN-α, IL-1α, and IL-6 showed contrasting results depending from the virus used and the time of infection. Conclusions. Additional investigations of co-infection or superinfection may be useful to figure out the potential relationship implicated in the outcome of viral respiratory infection in human population.