Production of antibodies to Staphylococcus aureus serotypes 5, 8, and 336 using poly(DL-lactide-co-glycolide) microspheres

Staphylococcus aureus is responsible for a major portion of the economic lo sses due to mastitis. Attempts to produce a vaccine to prevent S. aureus ma stitis have been hampered by the low immunogenicity of the polysaccharide, which forms on the surface of the organism when it enters the mammary gland . The polysaccharide inhibits phagocytosis and destruction of the organism by neutrophils. This study was conducted to determine if S. aureus polysacc haride serotypes 5, 8, and 336 conjugated to a protein and incorporated in poly(DL-lactide-co-glycolide) microspheres would enhance the production of opsonizing antibodies to the polysaccharide. Cows were immunized with eithe r polysaccharide conjugates emulsified in Freund's incomplete adjuvant or p olysaccharide conjugates encapsulated in poly (DL-lactide-co-glycolide) mic rospheres emulsified in Freund's incomplete adjuvant. All cows produced sus tained antibody titers to the three polysaccharide serotypes. Cows immunize d with microspheres had higher antibody titers. Cows in both groups produce d increased concentrations of IgG(1) and IgG(2) antibodies; neither group p roduced an increase in IgM. Immune sera from cows immunized with conjugates alone increased phagocytosis, which decreased at the end of the study. Ser a from cows immunized with conjugates in microspheres increased phagocytosi s, which was sustained at the end of the study. Immune sera from both group s decreased bacterial adherence to bovine mammary epithelial cells. These d ata showed that a single injection of antigen in microspheres produced high er titers and more sustained enhancement of phagocytosis, which could aid i n the defense of the cow against S. aureus infections.