Local and systemic humoral response to ovine mastitis caused by Staphylococcus epidermidis

Abstract

Objectives:Mastitis is responsible for a decrease in milk yield and quality. Disease control is vital for producers’ profit and for consumer’s welfare. This study aimed at investigating the immune response to Staphylococcus epidermidis intramammary infection.Methods:A total of 14 S. epidermidis isolates from milk collected from ewes with subclinical mastitis were used. Protein extracts were prepared and analysed by sodium dodecyl sulphate–polyacrylamide gel electrophoresis. Immunoblotting assay was performed for the detection of specific IgG and IgA in blood and milk from S. epidermidis mastitic ewes and from healthy animals.Results:The presence of pathogen-specific IgG was detected in blood of both infected and healthy animals. However, in milk, pathogen-specific IgG was only identified in infected animals, while IgA was found in both groups. Proteins with 59 and 43 kDa were recognized by all immunoglobulins screened in blood and milk provided by both healthy and mastitic ewes. In addition, in milk, IgG and IgA for proteins with 35 kDa were also detected.Conclusion:The results have lead to propose a theory for immunoglobulin dynamics in mammary gland’s defence: blood IgG1, specifically targeting intestinal antigens, is transported to the mammary gland with the main purpose of protecting the newborn, while IgG2 is specific for mammary pathogens and is transported to the mammary gland exclusively during inflammation. This study suggests that only local immunization should trigger IgG-producing cells in the mammary gland as a response to mastitis antigens. Moreover, IgA seems to be of crucial value for the defence of the ewe mammary gland, and stimulation strategies towards an increase in IgA should be addressed for mastitis prevention.

Mastitis in Small Ruminants

“…It has been suggested that immunoglobulins in colostrum and milk, are transported from blood into the mammary secretions as part of normal physiological process during colostrum and milk production or through leakage into the mammary gland during inflammation. For example, during normal physiological process, such as colostrum or milk production, blood derived IgG1 specific to intestinal antigens is trafficked into the mammary glands, blood derived IgG1 is produced by plasma cells derived from stimulated B lymphocytes of the Peyer's patches [111][112][113][114], and has no major role in intramammary infection. However, blood derived IgG2 leaks into the mammary glands during inflammation and is though to play a significant role in intramammary infection, as it is produced by plasma cells in the skin-associated lymphoid tissue and regional lymphoid tissues [111][112][113][114].…”

“…For example, during normal physiological process, such as colostrum or milk production, blood derived IgG1 specific to intestinal antigens is trafficked into the mammary glands, blood derived IgG1 is produced by plasma cells derived from stimulated B lymphocytes of the Peyer's patches [111][112][113][114], and has no major role in intramammary infection. However, blood derived IgG2 leaks into the mammary glands during inflammation and is though to play a significant role in intramammary infection, as it is produced by plasma cells in the skin-associated lymphoid tissue and regional lymphoid tissues [111][112][113][114]. Blood derived IgG2 has specificity to bacterial antigens associated to skin infections [111][112][113][114].…”

“…However, blood derived IgG2 leaks into the mammary glands during inflammation and is though to play a significant role in intramammary infection, as it is produced by plasma cells in the skin-associated lymphoid tissue and regional lymphoid tissues [111][112][113][114]. Blood derived IgG2 has specificity to bacterial antigens associated to skin infections [111][112][113][114]. In addition, during intramammary infection, antigen-activated plasma cells from regional lymphoid nodes present within the mammary glands produce IgA, IgM and IgG2 that are specific for antigens present in the mammary gland [111][112][113][114].…”

“…Blood derived IgG2 has specificity to bacterial antigens associated to skin infections [111][112][113][114]. In addition, during intramammary infection, antigen-activated plasma cells from regional lymphoid nodes present within the mammary glands produce IgA, IgM and IgG2 that are specific for antigens present in the mammary gland [111][112][113][114]. IgG1, IgG2 and IgM function by opsonising, invading bacterial pathogens and make them detectable by neutrophils and macrophages for opsonophagocytic destruction [115].…”

“…However, this defense mechanism can be hindered by toxins produced by S. aureus such as leukotoxin. IgA acts as a neutralizing antibody to protect the mammary gland against bacterial toxins [114]. In addition, IgA prevents the establishment of mastitis in the mammary gland through complement fixation, prevention of adhesion of pathogenic microbes to the endothelial lining by binding various adhesion receptors, and inhibition of bacterial metabolism by blocking enzymes [113], such as Staphyloccocus Enterotoxins.…”