Analysis of wild-type and C mutant human HPIV1 and interferon beta treatment in human respiratory epithelial A549 cells. Homo sapiens

HPIV1 is an important respiratory pathogen in children and the most common cause of viral croup. We performed a microarray-based analysis of gene expression kinetics to examine how wild-type (wt) HPIV1 infection altered gene expression in human respiratory epithelial cells and what role IFN-beta played in this response. We similarly evaluated HPIV1-P(C-), a highly attenuated and apoptosis-inducing virus that does not express any of the four C proteins, and HPIV1-C(F170S), a less attenuated mutant that contains a single point mutation in C and, like wt HPIV1, does not efficiently induce apoptosis, to examine the role of the C proteins in controlling host gene expression. We also used this data to investigate whether the phenotypic differences between the two C mutants could be explained at the transcriptional level. Mutation or deletion of the C proteins of HPIV1 permitted the activation of over 2000 cellular genes that otherwise would be repressed by HPIV1 infection. Thus, the C proteins profoundly suppress the response of human respiratory cells to HPIV1 infection. Cellular pathways targeted by the HPIV1 C proteins were identified and their transcriptional control was analyzed using bioinformatics. Transcription factor binding sites for IRF and NF-kappaB were over-represented in some of the C protein targeted pathways, but other pathways were dominated by less known factors such as forkhead transcription factor FOXD1. Surprisingly, the host response to the C knockout and C(F170S) mutants was very similar, and thus the phenotypic differences between these two viruses could not be explained at the host cell transcriptional level. Keywords: Time course; response to viral infection; response to IFN-beta Overall design: A549 cells were infected with wt HPIV1, C(F170S), or P(C-) in triplicate, and RNA was isolated at 6, 12, 24, and 48 hours. A549 cells were also treated with IFN-beta in triplicate, and RNA was isolated at 6 and 24 hours. Mock infection/treatment was performed in triplicate at each corresponding time point. Overall, 42 samples and microarrays were analyzed.