Characterisation of bovine dendritic cells following FMDV infection

Dendritic cells (DCs) are the sentinels of the immune system, responsible for recognising invading pathogens and priming the adaptive immune system for appropriate responses. Hence they are considered potential targets for vaccines against pathogens such as foot-and-mouth disease virus (FMDV). Little is known of the events of FMDV replication in bovine moDCs. Present work therefore sought to characterize FMDV and its immune complex (IC) replication in bovine moDCs in vitro. A chimeric heparin sulphate FMDV (O1M) was used in this study. Immuno-fluorescence microscopy (IFM) and quantitative RT-PCR was used to analyse viral replication at 0–6, 8, 16 and 24 hpi. Plaque assays were used to investigate the yields of live virus produced in moDCs at 0, 4, 8 and 24 hpi. FMDV and IC FMDV could infect moDC. In moDC infected with FMDV alone, or with immune-complexed (IC) FMDV, replication was observed by IFM between 2–4 and 1–16 hpi. In contrast, for both FMDV and FMDV IC infections RT-PCR analyses showed viral replication peaked at 4 hpi and then decreased between 8 to 24 hpi. Plaque assays using supernatants of the infected moDC showed no evidence of an increase in viral titre at 24 hpi. The detection of viral nsp (3AB and derivatives) suggests replication of FMDV persists for longer in moDCs when entry is mediated by IC. However, the lack of increase in virus yield suggests replication is abortive. One possible explanation for this difference could be that bovine moDCs are able to recognise non-immune complexed FMDV more rapidly.