Streptococcus uberis-specific T cells are present in mammary gland secretions of cows and can be activated to kill S. uberis

Abstract

The presence, phenotype and function of Streptococcus uberis-specific T cells in the mammary gland secretion (MGS) and blood of cows exposed to S. uberis were assessed. MGS T cells in the udder were purified and incubated with autologous blood monocytes as antigen-presenting cells (APC). Most cows, irrespective of prior S. uberis infection status and lactation status, were shown to have S. uberis-specific T cells both in MGS and in the blood. When cells from a subgroup of cows were studied, it was found that the S. uberis-specific T cells produced high levels of interferon-gamma (IFN-γ), but low levels of interleukin-10 (IL-10). A high percentage of responding T cells were of the CD8(+) memory (CD45RO) subset. T cells from the MGS specific for S. uberis were propagated from animals during the drying off period and expanded in vitro using interleukin-2 (IL-2) and S. uberis antigens. This led to the accumulation of T cells of the CD8(+) subset bearing memory cell markers (CD45A(-), CD45RO(+)), which released high levels of IFN-γ. Four of the five T cell lines derived from the MGS of three animals had substantial direct killing activity towards S. uberis in vitro. It is concluded that there is an emergence of S. uberis-specific bactericidal T cells in the MGS of cows after infection or environmental exposure to S. uberis. Vaccines aimed at activating and expanding this T cell population in the mammary glands of cattle may offer an avenue for the prevention of mastitis caused by S. uberis.

An update on environmental mastitis: Challenging perceptions

“…Vaccination with S. uberis enhances the proliferative response of peripheral blood lymphocytes to S. uberis antigens and induces an antigen-specific cytotoxic effect against blood monocytes/macrophages that have phagocytosed S. uberis (Hill et al, 1994;Wedlock et al, 2014). It is hoped that better understanding or manipulation of the cellular immune response to S. uberis may contribute to successful vaccine development (Denis et al, 2011;Schukken et al, 2011b), but it remains a challenge to activate and harness the cell-mediated arm of the immune response in the unique immunological environment of the mammary gland (Bharathan & Mullarky, 2011).…”

Trends Intherapeutic and Prevention Strategies for Management of Bovine Mastitis: An Overview

“…Sortase-anchored proteins derived from S uberis may be potential candidates for vaccine as they are important potential virulence antigens contributing to the pathogenesis of bovine mastitis [184]. Recently, Denis et al [185] reported that cows which developed mastitis after environmental exposure to S uberis developed bactericidal antibodies and T cells in blood and milk, resulting in an increased level of interferon-gamma (IFN-γ) that was specific for in-vitro killing of S uberis [185]. Clearly, research on the development of an effective vaccine against S uberis -associated mastitis is highly warranted.…”

Faibles concentrations cellulaires du lait et sensibilité aux mammites des ruminants laitiers

“…On sait que ces lymphocytes présentent un phénotype qui les fait qualifier de cellules mémoires (Taylor et al, 1994). Quelques travaux indiquent que les lymphocytes T CD8+ peuvent avoir une activité antibactérienne (Denis et al, 2011), mais aussi qu'ils peuvent avoir une activité immunosuppressive sur les fonctions des lymphocytes T CD4+ (Shafer-Weaver et Sordillo, 1997). Les fonctionnalités des lymphocytes T auxiliaires CD4+ que l'on trouve dans le lait n'ont pas été caractérisées.…”