Impact of a teat disinfectant based on Lactococcus cremoris on the cow milk proteome.

BACKGROUND: Dairy cow milking practices require cleaning and disinfection of the teat skin before and after milking to ensure the safety and quality of milk and prevent intramammary infections. Antimicrobial proteins of natural origin can be valuable alternatives to traditional disinfectants. In a recent field trial, we demonstrated that a teat dip based on a nisin A-producing Lactococcus cremoris (L) had comparable efficacy to conventional iodophor dip (C) in preventing dairy cow mastitis. Here, we present the differential shotgun proteomics investigation of the milk collected during the trial. METHODS: Four groups of quarter milk samples with low (LSCC) and high somatic cell count (HSCC) collected at the beginning (T0) and end (TF) of the trial were analyzed for a total of 28 LSCC (14 LSCC T0 and 14 LSCC TF) and 12 HSCC (6 HSCC T0 and 6 HSCC TF) samples. Milk proteins were digested into peptides, separated by nanoHPLC, and analyzed by tandem mass spectrometry (LC-MS/MS) on an Orbitrap Fusion Tribrid mass spectrometer. The proteins were identified with MaxQuant and interaction networks of the differential proteins were investigated with STRING. The proteomics data have been deposited to the ProteomeXchange Consortium via the PRIDE partner repository with the dataset identifier PXD045030. RESULTS: In healthy milk (LSCC), we detected 90 and 80 differential proteins at T0 and TF, respectively. At TF, the Lactococcus group showed higher levels of antimicrobial proteins. In mastitis milk (HSCC), we detected 88 and 106 differential proteins at T0 and TF, respectively. In the Lactococcus group, 14 proteins with antimicrobial and immune defense functions were enriched at TF vs. 4 proteins at T0. Cathelicidins were among the most relevant enriched proteins. Western immunoblotting validation confirmed the differential abundance. CONCLUSIONS: At T0, the proteomic differences observed in healthy milk of the two groups were most likely dependent on physiological variation. On the other hand, antimicrobial and immune defense functions were higher in the milk of cows with mammary gland inflammation of the Lactococcus-treated group. Among other factors, the immunostimulatory action of nisin A might be considered as a contributor.

Peptidomic changes in the milk of water buffaloes (Bubalus bubalis) with intramammary infection by non-aureus staphylococci.

Mastitis by non-aureus staphylococci (NAS) is a significant issue in dairy buffalo farming. In a herd with subclinical NAS mastitis, we identified Staphylococcus microti as the predominant species. To assess milk protein integrity and investigate potential disease markers, we characterized 12 NAS-positive and 12 healthy quarter milk samples by shotgun peptidomics combining peptide enrichment and high-performance liquid chromatography/tandem mass spectrometry (LC-MS/MS). We observed significant changes in the milk peptidome. Out of 789 total peptides identified in each group, 49 and 44 were unique or increased in NAS-positive and healthy milk, respectively. In NAS-positive milk, the differential peptides belonged mainly to caseins, followed by milk fat globule membrane proteins (MFGMP) and by the immune defense/antimicrobial proteins osteopontin, lactoperoxidase, and serum amyloid A. In healthy milk, these belonged mainly to MFGMP, followed by caseins. In terms of abundance, peptides from MFGMP and immune defense protein were higher in NAS-positive milk, while peptides from caseins were higher in healthy milk. These findings highlight the impact of NAS on buffalo milk quality and mammary gland health, even when clinical signs are not evident, and underscore the need for clarifying the epidemiology and relevance of the different NAS species in this dairy ruminant.

Influence of subclinical mastitis and intramammary infection by coagulase-negative staphylococci on the cow milk peptidome.

Coagulase-negative staphylococci (CNS) are the most prevalent microorganisms isolated from cow milk and are associated with subclinical mastitis and persistent increases in the bulk milk somatic cell count (BMSCC) of low BMSCC herds. By combining peptide enrichment, LC-ESI-MS/MS, and statistical analysis, we investigated the influence of subclinical mastitis and CNS infection on the milk peptidome. Quarter milk samples from clinically healthy Holstein cows were subjected to bacteriological culture (BC) and somatic cell counting (SCC) for two consecutive samplings and 28 (including 11 negatives and 17 positives) were selected for peptidomic analysis. The study identified 1363 different endogenous peptides and highlighted a significant increase of peptides in CNS-positive milk, mainly represented by casein fragments. Milk peptidome changes increased with the SCC, as also demonstrated by protein electrophoresis and densitometry. Peptides significantly different in CNS or CONTROL samples were identified and characterized. Our results indicate that subclinical mastitis by CNS can induce significant changes in the milk peptidome, opening the way to future studies for the identification of a biomarker panel as well as for the understanding of their consequences for the technological and sensorial characteristics of cow milk and dairy products. SIGNIFICANCE: This is the first investigation on the impact of subclinical CNS mastitis on the bovine milk peptidome. The peptide enrichment strategy combined with a highly sensitive MS/MS analysis enabled the compilation of a very large peptide dataset for healthy and mastitic milk. The comparison of CNS and Control samples, also considering SCC classes, highlighted several peptides with potential for understanding milk protein and peptide dynamics in subclinical mastitis, with possible implications for its detection.

COPZ1 depletion in thyroid tumor cells triggers type I IFN response and immunogenic cell death.

The coatomer protein complex zeta 1 (COPZ1) represents a non-oncogene addiction for thyroid cancer (TC); its depletion impairs the viability of thyroid tumor cells, leads to abortive autophagy, ER stress, UPR and apoptosis, and reduces tumor growth of TC xenograft models. In this study we investigated the molecular pathways activated by COPZ1 depletion and the paracrine effects on cellular microenvironment and immune response. By comprehensive and target approaches we demonstrated that COPZ1 depletion in TPC-1 and 8505C thyroid tumor cell lines activates type I IFN pathway and viral mimicry responses. The secretome from COPZ1-depleted cells was enriched for several inflammatory molecules and damage-associated molecular patterns (DAMPs). Moreover, we found that dendritic cells, exposed to these secretomes, expressed high levels of differentiation and maturation markers, and stimulated the proliferation of naïve T cells. Interestingly, T cells stimulated with COPZ1-depleted cells showed increased cytotoxic activity against parental tumor cells. Collectively, our findings support the notion that targeting COPZ1 may represent a promising therapeutic approach for TC, considering its specificity for cancer cells, the lack of effect on normal cells, and the capacity to prompt an anti-tumor immune response.