Staphylococcus aureus chronic intramammary infection modifies the expression of transforming growth factor beta (TGF-â) subfamily components during active involution

ANDREOTTI CS; PEREYRA EAL; BARAVALLE C; RENNA MS; ORTEGA HH; CALVINHO LF; DALLARD BE

Los Cocos, Cordoba

Congreso; First Argentinean Spring Course In Advanced Immunology, Los Cocos, Córdoba; 2013

During the nonlactating interval the mammary gland of dairy cows undergoes extensive remodeling. Some intramammary infections (IMI) can persist, leading to increased milk loss in the subsequent lactation. Staphylococcus aureus is a major pathogen causing primarily subclinical chronic mastitis, whose ability to withstand inflammatory responses have been associated with a decreased immune response. The objectives of this study were to determine whether S. aureus chronic IMI influences the expression of TGF-â subfamily components during active involution and to examine the histomorphometric changes that occur in mammary stroma and parenchyma and collagen I expression. Eighteen Holstein non-pregnant cows in late lactation were included in the study. Based on previous bacteriological studies and somatic cell counts (SCC), animals were either uninfected or naturally infected with S. aureus. Cows were slaughtered at 7, 14 and 21 d after cessation of milking and samples for immunohistochemical (IHC) and morphometric analysis were taken. The specificity of antibodies used in IHC was verified by western blot. Expression of the three TGF-â isoforms and type 1 and 3 receptors, as well as collagen I, was significantly higher in chronically infected quarters than in uninfected controls at the three involution stages studied. In infected quarters the highest expression of TGF-â1, TGF-â3, TGF-âR1 and TGF-âR3 was observed at 14 d of involution. The percentages of tissue area composed of parenchyma and intralobular stroma were significantly higher in S. aureus?infected than in uninfected quarters. The percentages of interlobular stromal area remained unchanged in infected quarters throughout the sampling period and were significantly lower than percentages in uninfected quarters. Chronic S. aureus mastitis modifies expression of the three TGF-â isoforms and type 1 and 3 receptors, which was associated with changes directed to limit the scope of inflammation and injury to the host.