5. Effect of exogenous IFN on HAstV replication. IF analysis of CaCo-2 cells after a 24 h pretreatment with 1,000 U IFN/ml and infection at different MOIs. Quantitative measurement of HAstV, EMCV, and RV progeny release in the supernatant of untreated cells and IFN-treated cells. Data represent mean values of 23 independent experiments and error bars represent the SEM. Asterisk indicates a statistically significant difference between mean titers from untreated and IFN-treated samples . doi:10.1371/journal.pone.0123087.g005 10 / 18 HAstV Delays SB203580 chemical information Interferon Induction qRT-PCR. EMCV and RV yields were measured by TCID50 titration in Vero and MA-104 cells, respectively. Reduction of HAstV replication after IFN pre-treatment was significant in all cases, but on average, there was a reduction of 0.8 0.2 log, which was less than what was observed with EMCV. As expected, RV was not affected by IFN-treatment. HAstV infection is not able to block IFN response induced by dsRNA In order to examine whether infection with HAstV inhibits the ability of cells to produce IFN in response to treatment with polyI:C, CaCo-2 cells were mock-infected or infected with HAstV at a MOI of 1, and transfected with polyI:C at 8 hpi. Twenty-four hours later, total RNA was analyzed by qRT-PCR to determine the level of IFN- mRNA induction, and supernatant of cells was collected to measure antiviral activity using the virus infectivity reduction bioassay. CaCo-2 cells infected with rotavirus at a MOI of 5, which is known to block the IFN response, were used as a positive control. Results suggest that HAstV infection is not able to disrupt the innate immune sensing pathway induced by polyI:C. Only a previous infection with RV was able to reduce by 60% Fig 6. HAstV is not able to inhibit the IFN response induced by polyI:C transfection. CaCo-2 cells were either mock-infected, infected with HAstV at a MOI of 1 or RV at PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19768747 a MOI of 5, and 8 hours later, they were mock-transfected or transfected with polyI:C. Level of IFN- mRNA normalized versus GAPDH produced within each experimental condition at 32 hpi. Level of antiviral activity in the supernatant of cultures at 32 hpi. Results are expressed as relative values to the reference control. Data represent mean values of 2 independent experiments and error bars represent the SEM. doi:10.1371/journal.pone.0123087.g006 11 / 18 HAstV Delays Interferon Induction the IFN- mRNA levels produced 
after polyI:C transfection, although differences were not statistically significant. HAstV and RV yields were similar between mock-transfected wells and wells transfected with polyI:C. As expected, antiviral activity in the supernatant of cultures at 32 hpi could only be detected in cells transfected with polyI:C, and the response could only be reduced by the presence of rotavirus infection. Higher percentage of infected cells correlates with higher levels of transepithelial resistance disruption and higher levels of IFN- response, but type I IFN does not cause a change in the TER Since it has been described that HAstV infection increases barrier permeability on differentiated CaCo-2 cells, we examined whether there was a correlation between disruption of intestinal barrier, the number of PubMed ID:http://www.ncbi.nlm.nih.gov/pubmed/19768759 infected cells and the IFN- response. Cells were differentiated and polarized on semipermeable inserts and infected apically at a MOI of 2 or 10. In these experiments, virus inoculum was not activated with trypsin in order to preserve cell monolayer. Activation of