Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/3/1998
Publication Date: N/A
Interpretive Summary: Mastitis is the most significant cause of economic loss to both the dairy and beef industries and Staphylococcus aureus is the most ubiquitous mastitis causing pathogen. Staphylococcus aureus results in the greatest economic loss of all the mastitis-causing pathogens. White blood cells (WBC) are the best defense against invading S. aureus, but they yrequire antibodies that both recognize the organism and are in turn bound and recognized by the WBC. A major obstacle to affective destruction of S. aureus by WBC is the production of a polysaccharide capsule by the organism. The capsule masks recognition by the antibody on the WBC. Because polysaccharides do not readily stimulate the production of protective antibodies by the immune system, researchers have sought means of boosting the animals response by binding the polysaccharide to a more immunogenic molecule. This study took this process a step further by incorporating the bound polysaccharide into microspheres that are taken up by antibody producing cells and that release the polysaccharide slowly over a long period of time. Cows immunized only once with the bound polysaccharide in microspheres produced high levels of antibodies to the capsule that remained elevated to the end of the study. These antibodies increased WBC uptake of S. aureus. This method of immunizing cows should increase their ability to ward off S. aureus infections, thus reducing the need for antibiotic treatment. The single injection will be especially useful in the beef industry where animal handling is less frequent than in the dairy industry.
Technical Abstract: Staphylococcus aureus is a major mastitic pathogen. Neutrophil phagocytosis is the major defense against S. aureus infection of the bovine mammary gland. Specific antibodies to S. aureus enhance phagocytosis. However, ninety-eight to 100% of bovine S. aureus mastitis isolates are encapsulated with a polysaccharide capsule that is low in immunogenicity. Capsular serotypes 5, 8, and 336 account for 100% of bovine S. aureus mastitis isolates. Cows were immunized with either purified capsular polysaccharides conjugated to carrier proteins emulsified in Freund's incomplete adjuvant (FICA) or the conjugates were encapsulated in poly(DL-lactide-co-glycolide) microspheres and emulsified in FICA. All cows produced antibodies to the three capsular serotypes which remained above prebleed titers to the end of the study. Cows immunized with the conjugates in microspheres had higher antibody titers than cows immunized with the conjugates in FICA alone. Cows in both groups produced antibodies of the IgG1 and IgG2 isotypes; neither group produced an increase in IgM. Sera from cows immunized with conjugates in FICA increased phagocytotis which decreased toward the end of the study. Sera from cows immunized with conjugates in microspheres increased phagocytosis which was sustained to the end of the study. These data show that microspheres can be used to produce higher titers and more sustained levels of antibodies which enhance phagocytosis and may aid in the defense of the cow against S. aureus infections.