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; Bannantine, John; MOOYOTTU, S. - Iowa State University; 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., Bannantine, J.P., Mooyottu, S., 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. Vol.11, article 773938. 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: Macrophages are important cells in host defense in ruminant paratuberculosis, a chronic enteritis caused by Mycobacterium avium subsp. paratuberculosis (MAP). Classical macrophage functions of pathogen trafficking, degradation, and antigen presentation are interrupted in mycobacterial infection. Additionally, immunologic roles of 25-hydroxyvitamin D3 (25(OH)D3) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) in bovine macrophage function have become of interest in recent years. The present study aimed to investigate the role of vitamin D3 on macrophage phenotype and endosomal trafficking of MAP in monocyte-derived macrophages (MDMs) cultured from healthy, subclinical, and clinically infected cattle. MDMs were pre-treated with ' 100 ng/ml 25(OH)D3 or ' 4 ng/ml 1,25(OH)2D3 and incubated 24 hrs with 10:1 MAP. In vitro MAP infection upregulated pro-inflammatory (M1) CD80 and downregulated resolution/repair (M2) CD163. Vitamin D3 generally decreased CD80 and increased CD163 expression. Early endosomal marker Rab5 was upregulated 140× across all three stages of infection following in vitro MAP infection; however, Rab5 was reduced in activated MDMs from subclinical and clinical cows compared to healthy controls. Rab7 expression decreased in control and clinical cows following MDM infection with MAP. Both forms of vitamin D3 reduced Rab5 expression in infected MDMs from control cows, while 1,25(OH)2D3 decreased Rab7 expression in control and subclinical animals regardless of MAP infection in vitro. Vitamin D3 promoted phagocytosis in MDMs from clinical cows and healthy controls treated with either vitamin D3 analog. Results from this study show exogenous vitamin D3 influences macrophage phenotype and impacts the expression of Rab GTPase within MDM culture.