Short communication: Differential immunoglobulin transfer during mastitis challenge by pathogen-specific components

Mastitis induced by Escherichia coli is often characterized by severe clinical signs, indicating a more powerful combat of the immune system against the pathogen compared with Staphylococcus aureus infections, which are often represented by chronic and subclinical diseases. The aim of this study was to test the major pathogenic component lipopolysaccharide (LPS) from E. coli and lipoteichoic acid (LTA) from Staph. aureus for their effects on blood-milk barrier integrity and the related transfer of immunoglobulins and lactate from blood into milk. A similar somatic cell count (SCC) increase was achieved by intramammary challenge of 1 quarter of 5 cows with 20 µg of LTA, and 8 cows with 0.2 µg of LPS (maximum log SCC/mL: 7). Milk IgG1 concentrations increased in LPS- but not in LTA-challenged quarters. Milk IgG2 concentrations were increased in treated quarters at 3 h after LPS, and 6 h after LTA challenge. Higher maximum levels of IgG2 were reached in milk of LPS-treated quarters (173 ± 58 μg/mL) than of LTA-challenged quarters (62 ± 13 μg/mL). Immunoglobulin G1 and IgG2 levels did not change in control quarters. l-Lactate concentrations in milk increased 4 h after LPS and 5 h after LTA challenge and reached higher maximum levels in LPS- (221 ± 48 mg/L) than in LTA-treated quarters (77 ± 18 mg/L). In conclusion, a mammary inflammation on a quantitatively similar level based on SCC increase achieves a more efficient transfer of blood components such as IgG2 via the blood-milk barrier if induced by LPS from E. coli than by LTA from Staph. aureus. This pathogen-specific difference may play an important role in the cure rate of the respective intramammary infection, which is usually lower in Staph. aureus- than in E. coli-induced mastitis.