Generation of human C3a, C4a, and C5a anaphylatoxins by protein A of Staphylococcus aureus and immobilized protein A reagents used in serotherapy of cancer.
Protein A (SpA) alone or immobilized on bacteria (e.g., Cowan strain I), collodion charcoal, or on Sepharose have been used in serotherapy of cancer in humans and experimental animals. Because SpA forms complexes with IgG that can activate complement, and the physiologic response during treatment often involves hypocomplementemia and reactions that are similar to those induced by anaphylatoxins, we used sensitive and specific radioimmunoassays to test the ability of SpA reagents to generate C3a, C4a, and C5a from human serum. The yield of anaphylatoxins depended on the dose of SpA, with the maximum generation of C3a (47 to 55 micrograms/ml) and C5a (1.4 to 1.9 micrograms/ml) being produced with levels of SpA that were maximally precipitated from serum. Maximum C4a levels (up to 15 micrograms/ml) were obtained at concentrations of SpA equal to or greater than the dose required to give optimal precipitation. The maximum concentrations of anaphylatoxins correspond to essentially quantitative conversions of C3 to C3a, C4 to C4a, and 40% of C5 to C5a after correction for levels found in serum incubated in pyrogen-free saline. Preformed insoluble complexes prepared from either serum or monomeric IgG also were capable of generating anaphylatoxins in fresh whole serum up to levels approximately equal to those observed in serum treated directly with an optimal amount of SpA. The preformed complexes from serum or IgG generated similar high concentrations of anaphylatoxins when carried through four sequential incubations with fresh serum, and complexes that contained approximately 1 microgram SpA were still active. Preincubating the insoluble complexes with chicken anti-SpA serum did not alter their activity. Incubation of serum with collodion charcoal coated with SpA, in a system that models the perfusion technique used to treat cancer, produced complexes that generated significant levels of C3a compared with levels found in serum passaged over albumin charcoal or in untreated serum. The C3a levels in serum from the albumin collodion charcoal were not significantly different from those found in untreated serum. Similar amounts of C3a, C4a, or C5a were observed in serum incubated with differing numbers of bacteria representing a strain of S. aureus rich in cell bound SpA (Cowan strain I) or a strain (Wood 46) deficient in SpA. This suggests that in intact bacteria, cell wall factors other than SpA (e.g., peptidoglycan) are predominantly responsible for generating anaphylatoxins.(ABSTRACT TRUNCATED AT 400 WORDS)
D000706:Anaphylatoxins / Q000096:biosynthesis*; D000818:Animals; D002606:Charcoal / Q000494:pharmacology; D003176:Complement C3 / Q000096:biosynthesis; D015926:Complement C3a; D003181:Complement C4 / Q000096:biosynthesis; D015934:Complement C4a; D003182:Complement C5 / Q000096:biosynthesis; D015936:Complement C5a; D006801:Humans; D007116:Immunization, Passive; D009369:Neoplasms / Q000628:therapy*; D010452:Peptide Biosynthesis; D011817:Rabbits; D012685:Sepharose / Q000494:pharmacology; D013205:Staphylococcal Protein A / Q000494:pharmacology* / Q000627:therapeutic use; D013211:Staphylococcus aureus / Q000276:immunology
D000706:Anaphylatoxins; D003176:Complement C3; D003181:Complement C4; D003182:Complement C5; D013205:Staphylococcal Protein A; D002606:Charcoal; D015926:Complement C3a; D015934:Complement C4a; D015936:Complement C5a; D012685:Sepharose