Antigen-presenting cells from calves persistently infected with bovine viral diarrhoea virus, a member of the Flaviviridae, are not compromised in their ability to present viral antigen

Abstract

The aim of this study was to assess whether the infection of antigen-presenting cells (APC) in vivo, evident in calves persistently infected (PI) with bovine viral diarrhoea virus (BVDV), compromised their ability to stimulate virus-specific T cell responses. Major histocompatibility complex (MHC) molecule-identical cattle were identified from the inbred family at the Institute for Animal Health. One was PI and immunotolerant to BVDV. Virus was not isolated from the remaining calves, which were classified as BVDV-immune or BVDV-naïve depending on the presence or absence of BVDV-specific antibodies in sera. Two-colour flow-cytometric analysis of PBMC from the PI calf showed that 40% of CD14+ monocytes were infected in vivo. Monocytes from the PI calf (PI monocytes) were used as naturally infected ex vivo APC with CD4+ or CD8+ T cells isolated from the BVDV-naïve or BVDV-immune animals. PI monocytes stimulated proliferative responses with CD4+ and CD8+ T cells from BVDV-immune animals, but not from BVDV-naïve calves. This provided evidence for the presence of virus-specific CD4+ and CD8+ memory T cells after acute infection and indicated that ex vivo monocytes from PI, immunotolerant calves stimulated both MHC class I- and MHC class II-restricted T cell responses to BVDV. Additionally, naturally infected ex vivo monocytes cultured in vitro for 3 days stimulated effective T cell responses to the virus with which they were infected.