Abstract
Neutrophilic airway inflammation is highly prevalent in racehorses in training, with the term mild to moderate equine asthma (MMEA) being applied to the majority of such cases. Our proposed study is largely derived from the strong association between MMEA in racehorses and their entry into a race training program. The objectives of this study are to characterise the effect of training on the local pulmonary immune system by defining the gene and protein expression of tracheal wash (TW) derived samples from Thoroughbred racehorses prior to and following commencement of race training. Multiomics analysis detected 2138 differentially expressed genes and 260 proteins during the training period. Gene and protein sets were enriched for biological processes related to acute phase response, oxidative stress, haemopoietic processes, as well as to immune response and inflammation. This study demonstrated TW samples to represent a rich source of airway cells, protein and RNA to study airway immunity in the horse and highlighted the benefits of a multiomics methodological approach to studying the dynamics of equine airway immunity. Findings likely reflect the known associations between race-training and both airway inflammation and bleeding, offering further insight into the potential mechanisms which underpin training associated airway inflammation.
Highlights
Neutrophilic airway inflammation is highly prevalent in racehorses in training, with the term mild to moderate equine asthma (MMEA) being applied to the majority of such cases
Thoroughbred racehorses at two time points (T0-resting period, T1-training period) and an average of 10.8 × 1 06 (± 1.9) cells per sample were isolated, consistent with previously reported d ata[16,17]
A slightly greater neutrophil and lymphocyte percentage was detected in samples obtained from horses during the training period, there was no significant difference between groups for all immune cells in the differential cell counts (DCC)
Summary
Neutrophilic airway inflammation is highly prevalent in racehorses in training, with the term mild to moderate equine asthma (MMEA) being applied to the majority of such cases. The “open window” theory, reflecting a temporal association between intense training and increased susceptibility to opportunistic infection, is well recognized within the field of human exercise immunology[8,15] and may explain the association between increased tracheal mucus (a marker of MMEA) and both time in training and the isolation of Streptococcus zooepidemicus and non-haemolytic streptococci from respiratory tract secretions of racehorses in training[6] Such supportive information has the capacity to inform management practices which, in light of the inherent necessity for episodes of high speed exercise within a training regimen, are likely to focus on either opportunistic pathogen avoidance schemes and/or novel immunomodulation strategies
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