The Mx1 gene is nonfunctional (truncated) in certain mouse strains including DBA/2J and C57BL/6J, but even the nonfunctional murine form is fully interferon inducible [18],

suggesting that it does reflect the anti-influenza interferon response of the DBA/2J and C57BL/6J mice. Among these four genes, only Stat1 has been shown to be regulated by stress or 4SC-202 clinical trial hypoxia [19, 20]. Interestingly, it was not affected by the mock treatment in the presented study, perhaps because its sensitivity to regulation in this murine model is not high enough to respond to any stress/hypoxia due to the mock treatment. Indeed, its upregulation in the infection was much smaller compared to the other three interferon-related genes. Thus, the observation that expression of these four interferon-related mRNAs was not affected by the mock treatment supports the aforementioned notion that the procedure-associated effects in this model relate to a stress response that can be functionally separated from the

antiviral response. Differences between the two mouse strains Differences were observed in the magnitude of the response to both mock treatment and viral infection. The fact that both procedure and infection-related responses were more vigorous in the DBA/2J mice agrees with the previously described NVP-LDE225 overall stronger inflammation in this strain during IAV infection [1]. This may reflect a greater intrinsic propensity to inflammation, but also the higher rate of viral replication in this strain. We favor a combination of both models, as the procedure-dependent effects, too, were brisker in the DBA/2J mice. Limitations The relatively small sample size represents a limitation of this study. Nonetheless, statistical significance was reached for several variables. A larger sample size would likely reveal additional significant changes, such as procedure-dependent regulation of Il1b, at least in the DBA/2J strain, in which there currently is a tendency toward significance (mean fold increase

at 6 h in mock-treated mice = 2.8; p = 0.09). In addition, the small number of target mRNAs does not represent overall gene expression in the lung. Other methods such as RNA deep sequencing would likely reveal genes showing an earlier Acyl CoA dehydrogenase response to IAV infection or a longer persistence of procedure-dependent effects. Conclusions Despite the aforementioned limitations, the presented results clearly show that the manipulations surrounding the infection procedure can affect pulmonary gene expression in a host strain-dependent manner for approx. 24 h. Thus, “mock treatment” controls should be included in all murine studies on IAV infection where measurements are to be taken within approx. the first 24 h. Likewise, such controls are likely needed in similar studies with other viral and selleck chemical non-viral respiratory pathogens.