Transcriptomic analysis of persistent infection with foot-And-mouth disease virus in cattle suggests impairment of apoptosis and cell-mediated immunity in the nasopharynx

In order to investigate the mechanisms of persistent foot-And-mouth disease virus (FMDV) infection in cattle, transcriptome alterations associated with the FMDV carrier state were characterized using a bovine whole-Transcriptome microarray. Eighteen cattle (8 vaccinated with a recombinantFMDV A vaccine, 10 non-vaccinated) were challenged with FMDV A24 Cruzeiro, and the gene expression profiles of nasopharyngeal tissues collected between 21 and 35 days after challenge were compared between 11 persistently infected carriers and 7 non-carriers. Carriers and non-carrierswere furthercompared to 2 naïve animals that had been neither vaccinated nor challenged. At a controlled false-discovery rate of 10% and a minimum difference in expression of 50%, 648 genes were differentially expressed between FMDV carriers and non-carriers, and most (467) had higher expression in carriers.Among these, genes associated with cellular proliferation and the immune response-such as chemokines, cytokines and genes regulating T and B cells-were significantly overrepresented. Differential gene expression was significantly correlated between non-vaccinated and vaccinated animals (biological correlation +0.97), indicating a similar transcriptome profile across these groups. Genes related to prostaglandinE2 production and the induction of regulatoryT cells were overexpressed in carriers. In contrast, tissues from non-carrier animals expressed higher levels of complement regulators and pro-Apoptotic genes that could promote virus clearance. Based on these findings, we propose a working hypothesis for FMDV persistence in nasopharyngeal tissues of cattle, in which the virus may be maintained by an impairmentof apoptosis and the local suppression of cell-mediated antiviral immunity by inducible regulatoryT cells.