Modelling Bovine Granuloma Formation In Vitro upon Infection with Mycobacterium Avium Subspecies Paratuberculosis

Abstract

Mycobacterium avium subspecies paratuberculosis (Map) causes chronic granulomatous disease in cattle and ruminant livestock, causing substantial economic losses. Current vaccines delay clinical signs but cannot train the immune system to fully eradicate latent Map. During latency, Map uses host defenses, cage-like macrophage clusters called granuloma, as incubators for months or years. We used an in vitro model to investigate the early coordination of macrophages into granuloma upon Map infection over ten days. We found that at multiplicities of infection (MOI; Map:macrophages) of 1:2 and below, the macrophages readily form clusters and evolve pro-inflammatory cytokines in keeping with a cell-mediated immune response. At higher MOIs, viability of host macrophages is negatively impacted. At 1:4 MOI, we quantified viable Map in our model and confirmed that intracellular Map reproduced over the first five days of infection. Host cells expressed Type 1-specific cytokines, and Map-infected macrophages displayed reduced motility compared to Map-exposed, uninfected macrophages, suggesting an important role for uninfected macrophages in the early aggregative response. Reported is the first in vitro JD granuloma model capturing Map and macrophage viability, size distribution of resulting clusters, motility of monocyte-derived macrophages, and cytokine response during clustering, allowing quantitative analysis of multiple parameters of the Map-specific granulomatous response.

Early response of monocyte-derived macrophages from vaccinated and non-vaccinated goats against in vitro infection with Mycobacterium avium subsp. paratuberculosis

“…Despite the fact that TNF-α, IL-1β, IL-6 and IFN-γ cytokines have been implicated in the in vitro activation of Th1 immune response, the destruction of Map and the development of characteristic granulomas [ 58 – 61 ], the current study found no significant influence of vaccination or infection over the transcription of these cytokines by CaMØs, presumably due to the high individual variability. Previous in vitro studies have shown the effect of IFN-γ on the acidification and maturation of phagosomes in MDMs that reduce Mycobacterium avium subsp.…”

Alternatives to antibiotics in veterinary medicine: considerations for the management of Johne's disease

“…This poses an additional problem in terms of developing novel treatments and rapid diagnostic tests, as the pathogens effectively have a mammalian cell shield preventing the drug or the probe accessing its target. This becomes a greater issue as the infection progresses, as infected macrophages eventually differentiate into epithelioid cells, which aggregate to form granulomas to suppress bacterial growth (Martcheva et al ., 2015; Rice et al ., 2019). Within the granuloma, MAP enters a dormant state and can gradually reactivate in later stages of infection, resulting in intermittent shedding of MAP in mid-stage disease (Martcheva et al ., 2015; Rice et al ., 2019; Garvey, 2020).…”

Bacterial Species Associated With Human Inflammatory Bowel Disease and Their Pathogenic Mechanisms

“…MAP bacteria that travel across the intestinal epithelium are phagocytosed by macrophages via complement receptors. Infected macrophages form granulomas and become a latent infection or active disease ( Birkness et al, 2007 ; Rice et al, 2019 ).…”