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Introduction Mycoplasma bovis (M. bovis) manifests as diverse clinical pathologies in cattle that significantly impacts cow health and productivity worldwide. Current diagnostic methods rely on active infection to detect antibodies and bacterial DNA, however, these methods could be improved for subclinical infections. This is of particular importance in long-term surveillance programs in countries that have decided to eradicate M. bovis , such as New Zealand. Methods This study investigated small extracellular vesicles (sEV) from serum samples of M. bovis infected dairy cows to identify protein cargo that may be used as potential diagnostic markers during subclinical infection to complement current testing methods. Small EV were isolated from serum of dairy cows positive for M. bovis infection ( n = 45) and their protein cargo compared with those from serum sEV from non-infected dairy cows ( n = 49). Proteins were identified using liquid chromatography–ion mobility–tandem mass spectrometry in pooled samples ( n = 10/group), resulting in 695 non-redundant top proteins identified across all samples. Results Differential protein abundance analysis indicated 90 proteins significantly ( q -value 0.05) different in sEV of infected animals compared with controls. Proteins associated with inflammation and the complement system as well as proteins involved in the oxidative stress pathway, were in greater abundance in sEV from M. bovis positive animals compared with M. bovis negative animals. Several histone proteins and antimicrobial peptides exhibited lower abundance in sEV from M. bovis positive compared with negative cows. Conclusion Although this study has not identified a protein candidate specific enough for use as a single diagnostic marker, our results indicate a shift towards a diseased state in M. bovis infected dairy cows and provide valuable insight into sEV biology during M. bovis infection.
Ross et al. (Fri,) studied this question.