EXPRESSION PROFILE OF IMMUNE RESPONSE GENES IN GOATS WITH EXPERIMENTALLY INDUCED STAPHYLOCOCCUS AUREUS MASTITIS.

Counteracting infectious diseases of farm animals are an everlasting challenge in food production from livestock and preserving the health of farm animals is highly relevant to maintaining high standards of food quality. Clinical mastitis (CM) is the primary health reason for involuntary culling in dairy small ruminants and causes additional economic losses from costs of veterinary treatments. Complementary strategies are needed, since the classical prophylactic measures sometimes appear too demanding to breeders in terms of time and care, and efficient vaccination against the main pathogens is still lacking. There is evidence that Somatic Cell Count (SCC)-based selection should efficiently reduce CM incidence and currently selection strategies in cows and sheeps are based on a linear decrease of milk SCC. The effects and efficacy of SCC selection in goats are still unknown. A better understanding of the defense mechanisms affected and modified by SCC-based selection would be helpful to predict the indirect response for CM, pathogen-specific infections, and resistance to other diseases in the long term. Knowledge of these basic mechanisms will help to the design new and optimized strategies to prevent infections and, at the same time, significantly aid the improvement of food safety for the consumer. Microarray technology enables the examination of complex interactions between the host and bacterial pathogens. In dairy ruminants transcriptome profiling has enabled the identification of genes, pathways and regulatory networks activated in mammary tissues during experimental infection by various pathogens, including E. coli, S. aureus and S. uberis. Information in goats are still low and many host-pathogen interaction mechanisms have to be explained. In our study the bovine CustomArray 90K was used to evaluate the gene expression in milk somatic cells (MSCs) and blood of goats infected by S. aureus.The objectives of the present study were: (i) to identify the network of genes that becomes activated in caprine blood and MSCs in early response upon a S. aureus challenge in order to better understand the local and sistemic response and (ii) to search any difference in this immune response by using two animal groups belonging to a caprine reference family established based on founders with adverse SCC breeding values, (iii) to develop a set of internal reference genes useful to normalize RT-qPCR data in studies of gene expression in caprine MSCs. A total of 300 genes were found to be differentially expressed between 0 h and 24 h post infection and 128 genes between 0 h and 30 h post infection, with a p value < 0.01 and log2 fold change > 1.5. Among these, the majority were up-regulated. In leukocytes a total of 8 genes were up-regulated between 0h and 30h post infection with a p value < 0.01 and log2 fold change > 1.5 and 1 was down-regulated during IMI. The top up-regulated genes (5.65 to 3.16 fold change) plays an important role (i) in immune and inflammatory response (NFKB1, TNFAIP6, BASP1, IRF1, PLEK, BATF3); (ii) in the regulation of innate resistance to pathogens (PTX3); (iii) in the regulation of cell metabolism (CYTH4, SLC2A6, ARG2). The top down-regulated genes (-1.50 to –2.46 fold) included genes involved in lipid metabolism (ABCG2, FASN), chemokine, cytokine and intracellular signaling (SPPI), cytoskeleton and extracellular matrix (KRT19). No significant differences were found in the levels of the expression gene between the two group of animals. Results provided novel information into the early stage of S. aureus infection in goats. Moreover, this study provides a validated panel of optimal internal references genes which may be useful for the identification of genes differentially expressed by RT-qPCR in caprine MSCs. According to our evaluation, we recommend using G6PD and YWHAZ as reference genes to normalize gene expression data in caprine MSCs.