Selective IgG binding to the LPS glycolipid core found in bovine colostrum, or milk, during Escherichia coli mastitis influences endotoxin function.

The dynamic interplay between intramammary IgG, formation of antigen-IgG complexes and effector immune cell function is essential for immune homeostasis within the bovine mammary gland. We explore how changes in the recognition and binding of anti-LPS IgG to the glycolipid "functional" core in milk from healthy or clinically diagnosed Escherichia coli (E. coli) mastitis cows' controls endotoxin function. In colostrum, we found a varied anti-LPS IgG repertoire and novel soluble LPS/IgG complexes with direct IgG binding to the LPS glycolipid core. These soluble complexes, absent in milk from healthy lactating cows, were evident in cows diagnosed with E. coli mastitis and correlated with endotoxin-driven inflammation. E. coli mastitis milk displayed a proportional reduction in anti-LPS glycolipid core IgG compared to colostrum. Milk IgG extracts showed that only colostrum IgG attenuated LPS induced endotoxin activity. Furthermore, LPS-stimulated reactive oxygen species (ROS) in milk granulocytes was only suppressed by colostrum IgG, while IgG extracts of neither colostrum nor E. coli mastitis milk influenced N-formylmethionine-leucyl-phenylalanine (fMLP)-stimulated ROS in LPS primed granulocytes. Our findings support bovine intramammary IgG diversity in health and in response to E. coli infection generate milk anti-LPS IgG repertoires that coordinate appropriate LPS innate-adaptive immune responses essential for animal health.
Competing Interests: Declaration of conflicting interestsThe authors declared the following potential conflicts of interest with respect to the research, authorship, and/or publication of this article: The authors, SH, DF and RK are or were (DF) employees of Koru Diagnostics Ltd, confirm there is no individual personal financial relationship and declare that research was conducted in the absence of any commercial or financial relationship that could be construed as a potential conflict of interest. AP is a shareholder of Koru Diagnostics Ltd and as CSO was involved in conceptualisation, supervision, investigation and writing of the original draft. No payment or services from a third party was received for any aspect of the submitted work. In addition, selective concepts and data described in this manuscript are part of a patent submission by Koru Diagnostics Ltd, entitled “Method for Detecting Microorganisms and Uses Thereof” in November 2022. Patent Ref: PCT/NC2022/050136, #KDL1007PC. The raw data supporting the conclusions of this study are not readily available as they are proprietary and part of a pending patent submission. However, requests to access specific data should be directed to Koru Diagnostics Ltd info@korudiagnostics.com.