Lactoferrin affects the adherence and invasion of Streptococcus dysgalactiae ssp. dysgalactiae in mammary epithelial cells

Abstract

Streptococcus dysgalactiae spp. dysgalactiae is an important causative agent of bovine mastitis worldwide. Lactoferrin is an innate immune protein that is associated with many functions including immunomodulatory, antiproliferative and antimicrobial properties. This study aimed to investigate the interactions between lactoferrin and a clinical bovine mastitis isolate, S. dysgalactiae spp. dysgalactiae DPC5345. Initially a deliberate in vivo bovine intramammary challenge was performed with S. dysgalactiae DPC5345. Results demonstrated a significant difference in lactoferrin mRNA levels in milk cells between the control and infused quarters 7 hours post infusion. Milk lactoferrin levels in the S. dysgalactiae DPC5345 infused quarters were significantly increased compared to control quarters at 48 h post infusion. In vitro studies demonstrated that lactoferrin had a bacteriostatic effect on the growth of S. dysgalactiae DPC5345 and significantly decreased the ability of the bacteria to internalise into HC-11 mammary epithelial cells. Confocal microscopy images of HC-11 cells exposed to S. dysgalactiae and lactoferrin further supported this effect by demonstrating reduced invasion of bacteria to HC-11 cells. The combined data suggests that a bovine immune response to S. dysgalactiae infection includes a significant increase in lactoferrin expression in vivo and, based on in vitro data, lactoferrin limits mammary cell invasion of this pathogen by binding to the bacteria and preventing its adherence.

The Role of Streptococcus spp. in Bovine Mastitis

“…The protein has antimicrobial properties as it binds iron, which is essential for bacterial and viral replication [ 42 ]. Since iron demand of streptococcal species is rather low, lactoferrin was demonstrated to have a bacteriostatic effect on different streptococci [ 43 ]. Clinical trials attempted on seven Holstein Friesian cows showed that 67% of the mammary quarters infected with S. uberis wild-type showed clinical manifestations of mastitis (clots in produced milk, firm and moderate swelling of the mammary glands with red coloration).…”

“…After 8 h of exposure to lactoferrin, a dose-dependent growth inhibition of S. dysgalactiae was observed in a previous study due to the antimicrobial properties of the protein. In addition, assays conducted with HC-11 murine epithelial cells revealed lactoferrin-dependent decrease of bacterial adhesion [ 43 ]. Lactoferrin may serve as a bridging molecule for S. uberis , consequently promoting adherence and internalization into mammary epithelial cells, thereby surviving host defense mechanisms by immune evasion [ 46 ].…”

Emulsion-Based Postbiotic Formulation Is Comparable to Viable Cells in Eliciting a Localized Immune Response in Dairy Cows With Chronic Mastitis

“…Bacteriocins such as nisin A have demonstrated antibacterial activity against mastitis pathogens ( Malvisi et al, 2016 ). Immune stimulants such as ginseng ( Beccaria et al, 2018 ) and the use of plant-derived compounds ( Maia et al, 2018 ) and immune proteins such as lactoferrin ( O’Halloran et al, 2016 ) have also been tested in this regard. Probiotic lactic acid bacteria (LAB) strains have been reported to eliminate mastitis-causing staphylococcal biofilms ( Wallis et al, 2019 ).…”

Mini Review: Lactoferrin-binding protein of Streptococcus in Bovine Mastitis

“…Streptococcus is a bacterium that is often found in mastitis, including S. agalactiae, S. dysgalactiae, and S. uberis [4,5]. One of the virulence factors in streptococcus is a lactoferrin-binding protein (LBP), but there are differences among these organisms, especially the pathogenesis of milk lactoferrin protein to interact with streptococcus [6]. Lactoferrin is a host innate immune protein that acts as antibacterial, immunomodulator, antiadhesion, and has iron-binding properties [7,8,9].…”