Exogenous vitamin D3 modulates response of bovine macrophages to Mycobacterium avium subsp. paratuberculosis infection and is dependent upon stage of Johne's disease

Authors: WHERRY, T.L.T. - Iowa State University; Dassanayake, Rohana; Casas, Eduardo; MOOYOTTU, S. - Iowa State University; Bannantine, John; Stabel, Judith

Submitted to: Frontiers in Cellular and Infection Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/27/2021
Publication Date: 1/17/2022
Citation: Wherry, T., Dassanayake, R.P., Casas, E., Mooyottu, S., Bannantine, J.P., Stabel, J.R. 2022. Exogenous vitamin D3 modulates response of bovine macrophages to Mycobacterium avium subsp. paratuberculosis infection and is dependent upon stage of Johne's disease. Frontiers in Cellular and Infection Microbiology. https://doi.org/10.3389/fcimb.2021.773938.
DOI: https://doi.org/10.3389/fcimb.2021.773938

Interpretive Summary: Johne's disease is a chronic, debilitating intestinal disorder in cattle characterized by diarrhea, reduced feed intake, weight loss and death. Cattle usually become infected as young calves by ingesting feces containing the causative bacteria. However, symptoms of disease do not usually present themselves until the animals reach 3 to 5 years of age or even older. During this time the animal is infected and may be shedding the organism in its feces without showing any clinical signs of disease. In addition to reduced milk production by these animals, they also present a potential infective threat to the rest of the herd. Johne’s disease is difficult to diagnose and therefore to control. Understanding nutrition is a critical factor in improving overall health of the herd and reducing incidence of morbidity. Vitamin D is an important nutrient that is known for its role in calcium homeostasis. In addition, it has demonstrated roles in host immunity to bacterial pathogens. In the present study, the impact of infection with Mycobacterium avium subsp. paratuberculosis on vitamin D metabolism was investigated. This study demonstrated that cows naturally infected with Mycobacterium avium subsp. paratuberculosis have different responses than control noninfected cows and that macrophages from those cows respond to supplemental vitamin D3 differently. These data suggest that despite feeding high levels of vitamin D3 in the diet, efficient use of this nutrient/hormone may be retarded by chronic inflammatory reactions in infected cows and, therefore, may be impacting the ability of immune cells to respond to infection. Supplementing with vitamin D may be helpful to improve the cellular responses. Further work to elucidate the mechanism of vitamin D on immune cell function will help to determine its utility as a potential therapeutic during infectious disease.

Technical Abstract: Mycobacterium avium subspecies paratuberculosis (MAP), the causative agent of ruminant enteritis, targets intestinal macrophages. During infection, macrophages contribute to mucosal inflammation and development of granulomas in the small intestine which worsens as disease progression occurs. Vitamin D3 is an immunomodulatory steroid hormone with beneficial roles in host-pathogen interactions. Few studies have investigated immunologic roles of 25-hydroxyvitamin D3 (25(OH)D3) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in cattle, particularly cattle infected with MAP. This study examined the effects of exogenous vitamin D3 on immune responses of monocyte derived macrophages (MDMs) isolated from dairy cattle naturally infected with MAP. MDMs were pre-treated with ' 100 ng/ml 25(OH)D3 or ' 4 ng/ml 1,25(OH)2D3, then incubated 24 hrs with live MAP in the presence of their respective pre-treatment concentrations. Following treatment with either vitamin D3 analog, phagocytosis of MAP by MDMs was significantly greater in clinically infected animals, with a greater amount of live and dead bacteria. Clinical cows had significantly less CD40 surface expression on MDMs compared to subclinical cows and noninfected controls. 1,25(OH)2D3 also significantly increased nitrite production in MAP infected cows. 1,25(OH)2D3 treatment played a key role in upregulating secretion of pro-inflammatory cytokines IL-1' and IL-12 while downregulating IL-10, IL-6, and IFN-'. 1,25(OH)2D3 also negatively regulated transcripts of CYP24A1, CYP27B1, DEFB7, NOS2, and IL10. Results from this study demonstrate that vitamin D3 compounds, but mainly 1,25(OH)2D3, modulate both pro- and anti-inflammatory immune responses in dairy cattle infected with MAP, impacting the bacterial viability within the macrophage.