Infection of monocyte-derived macrophages with a reporter Map strain: Validation of the susceptibilty SNP (-298A/G) in the bovine MIF gene

Abstract

Johne’s disease (JD) is a chronic, infectious enteritis of ruminant animals caused by Mycobacterium avium subsp. paratuberculosis (Map). Monitoring host-pathogen interaction over time is critical to understanding the complex pathogenesis of JD. A major constraint in studying the host-pathogen interaction in JD infection is the inherent difficulty of detecting cells infected with Map. The purpose of the present study was to develop and use a fluorescent Map isolate to assess the association between SNP (-298 A>G) in the MIF gene with innate susceptibility to Map infection. In order to rapidly detect bacterial load within host cells, we cloned the gene encoding mCherry into a clinical isolate of Map. The recombinant Map clinical isolate expressing mCherry was used to quantify bacterial numbers, detect infected macrophages in vitro using fluorescent microscopy, determine effector killing of bacteria by macrophages and was tested in an in vivo calf infection study to assess its stability.