Abstract
BackgroundMastitis is still considered to be the most economically important infectious disease in dairy cattle breeding. The immune response in mammary gland tissues could help in developing support strategies to combat this disease. The role of neutrophils and macrophages in the innate response of mammary gland is well known. However, the immune response in mammary gland tissues, including levels of antimicrobial peptide transcripts, has not been well recognized. Moreover, most studies are conducted in vitro, on cell cultures, or on artificially infected animals, with analysis being done within a several dozen hours after infection.The aim of the study was to examine the in vivo transcript levels of beta-defensin and cathelicidins genes in cow mammary gland secretory tissue (parenchyma) with the chronic, recurrent and incurable mammary gland inflammation induced by coagulase-positive or coagulase-negative Staphyloccoci vs. bacteria-free tissue.ResultsThe mRNA of DEFB1, BNBD4, BNBD5, BNBD10 and LAP genes, but not of TAP gene, were detected in all investigated samples regardless of the animals’ age and microbiological status of the mammary gland, but at different levels. The expression of most of the beta-defensin genes was shown to be much higher in tissues derived from udders infected with bacteria (CoPS or CoNS) than from bacteria-free udders, regardless of parity. Cathelicidins (CATH4, CATH5 and CATH6) showed expression patterns contrasting those of β-defensins, with the highest expression in tissues derived from bacteria-free udders.ConclusionIncreased expression of genes encoding β-defensins in the infected udder confirms their crucial role in the defense of the cow mammary gland against mastitis. On the other hand, the elevated cathelicidin transcripts in non-infected tissues indicate their role in the maintenance of healthy mammary tissues. The expression levels of investigated genes are likely to depend on the duration of the infection and type of bacteria.Electronic supplementary materialThe online version of this article (doi:10.1186/s12917-014-0246-z) contains supplementary material, which is available to authorized users.
Highlights
Mastitis is still considered to be the most economically important infectious disease in dairy cattle breeding
The highest average number of somatic cells (SC) and the lowest lactose content were found in milks containing coagulase-positive Staphyloccoci in lactations 3/4 (Table 1)
Two different pairs of primers previously used by Whelehan et al [23] and Alva-Murillo et al [29] to detect tracheal antimicrobial peptide (TAP) mRNA in bovine mammary glands were used in the present study, but no expression of TAP mRNA was detected in the cows’ mammary gland parenchyma
Summary
Mastitis is still considered to be the most economically important infectious disease in dairy cattle breeding. The immune response in mammary gland tissues, including levels of antimicrobial peptide transcripts, has not been well recognized. Mastitis is defined as chronic, latent or acute inflammation of the mammary gland, and is still considered to be the most economically important infectious disease in dairy cattle breeding [1]. It is commonly believed that the environmental bacteria are less virulent than contagious ones, and are usually quickly eradicated by the host’s immune system [8,9] Opportunistic bacteria, such as coagulase-negative Staphylococci (CoNS) and Escherichia coli can cause clinical and severe mastitis depending on cow factors (host defense status) [2,3,4]. The studies conducted by Ryniewicz et al [17,18], Wojdak-Maksymiec et al, [19,20] and Bagnicka et al [21,22] showed associations between polymorphisms in β-defensin genes and SCC, which could be used in genomic selection against mastitis
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