Production of Antibodies to Staphylococcus aureus Serotypes 5, 8, and 336 Using Poly(DL-Lactide-co-Glycolide) Microspheres

¹ Immunology and Disease Resistance Laboratory, USDA, Agricultural Research Service, Beltsville, MD 20705
² NABI, 12880 Wilkins Ave., Rockville, MD 20852
³ Department of Animal and Avian Sciences, University of Maryland, College Park 20742

Staphylococcus aureus is responsible for a major portion of the economic losses due to mastitis. Attempts to produce a vaccine to prevent S. aureus mastitis 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 polysaccharide serotypes 5, 8, and 336 conjugated to a protein and incorporated in poly(DL-lactide-coglycolide) microspheres would enhance the production of opsonizing antibodies to the polysaccharide. Cows were immunized with either polysaccharide conjugates emulsified in Freund's incomplete adjuvant or polysaccharide conjugates encapsulated in poly (DL-lactide-co-glycolide) microspheres emulsified in Freund's incomplete adjuvant. All cows produced sustained anti-body titers to the three polysaccharide serotypes. Cows immunized with microspheres had higher antibody titers. Cows in both groups produced increased concentrations of IgG₁ and IgG₂ antibodies; neither group produced an increase in IgM. Immune sera from cows immunized with conjugates alone increased phagocytosis, which decreased at the end of the study. Sera from cows immunized with conjugates in microspheres increased phagocytosis, which was sustained at the end of the study. Immune sera from both groups decreased bacterial adherence to bovine mammary epithelial cells. These data showed that a single injection of antigen in microspheres produced higher titers and more sustained enhancement of phagocytosis, which could aid in the defense of the cow against S. aureus infections.

Key Words: microsphere • Staphylococcus aureus • capsule • phagocytosis

Submitted on January 20, 1999
Accepted on February 22, 2000

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