Global transcriptomic profiles of circulating leucocytes in early lactation cows with clinical or subclinical mastitis.

Hitoshi Takeda ,Mazdak Salavati ,Cinzia Marchitelli ,D C Wathes ,Zhangrui Cheng ,Laura Buggiotti ,Lanhua Tang ,A.r.g Wylie ,M.a Crowe ,Sergio Palma-Vera

doi:10.1007/s11033-021-06494-8

Abstract

Bovine mastitis, an inflammatory disease of the mammary gland, is classified as subclinical or clinical. Circulating neutrophils are recruited to the udder to combat infection. We compared the transcriptomic profiles in circulating leukocytes between healthy cows and those with naturally occurring subclinical or clinical mastitis. Holstein Friesian dairy cows from six farms in EU countries were recruited. Based on milk somatic cell count and clinical records, cows were classified as healthy (n = 147), subclinically (n = 45) or clinically mastitic (n = 22). Circulating leukocyte RNA was sequenced with Illumina NextSeq single end reads (30M). Differentially expressed genes (DEGs) between the groups were identified using CLC Genomics Workbench V21, followed by GO enrichment analysis. Both subclinical and clinical mastitis caused significant changes in the leukocyte transcriptome, with more intensive changes attributed to clinical mastitis. We detected 769 DEGs between clinical and healthy groups, 258 DEGs between subclinical and healthy groups and 193 DEGs between clinical and subclinical groups. Most DEGs were associated with cell killing and immune processes. Many upregulated DEGs in clinical mastitis encoded antimicrobial peptides (AZU1, BCL3, CAMP, CATHL1, CATHL2, CATHL4,CATHL5, CATHL6, CCL1, CXCL2, CXCL13, DEFB1, DEFB10, DEFB4A, DEFB7, LCN2, PGLYRP1, PRTN3, PTX3, S100A8, S100A9, S100A12, SLC11A1, TF and LTF) which were not upregulated in subclinical mastitis. The use of transcriptomic profiles has identified a much greater up-regulation of genes encoding antimicrobial peptides in circulating leukocytes of cows with naturally occurring clinical compared with subclinical mastitis. These could play a key role in combatting disease organisms.

Highlights

Bovine mastitis is an inflammatory disease of the mammary gland
The milk enzyme lactate dehydrogenase (LDH) was significantly higher at the time of blood sample collection in the cows with clinical mastitis compared with the healthy cows or those with subclinical mastitis (P < 0.0001) while NAGase showed a progressive increase healthy < subclinical < clinical (P < 0.05–0.0001, Supplementary file 4)
We identified 258 differentially expressed genes (DEG) in circulating leukocytes isolated from cows with subclinical mastitis and 769 DEGs from cows with clinical mastitis compared with the healthy cows

Summary

Introduction

Bovine mastitis is an inflammatory disease of the mammary gland. Mastitis can be caused by metabolic disorders, by tissue trauma and, most commonly, by environmental or contagious pathogenic microorganisms [1, 2]. The annual costs to the dairy industry of dealing with mastitis have been estimated at over $2 billion per annum in both Europe and the USA [3, 4]. There have been huge investments over many years into the development of new strategies for the prevention, diagnosis and management of mastitis, but it remains the most economically significant bacterial disease of dairy cattle worldwide [2]. Continued advances in mastitis control are necessary to ensure sustainability of dairy farming

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Conclusion