FIG. 3.

Bactericidal activity of antisera raised against recombinant Opc protein preparations. Pooled antisera raised against Opc+MPLA liposomes, which showed greatest activity against the homologous strain (MC58 Opc⁺⁺), was also tested against strain H44/76, expressing the homologous Opc protein (Opc⁺), and strain MC139, expressing a heterologous protein with high (Opc⁺⁺) and low (Opc⁺) levels of expression. Serum was tested at dilutions of 1:4, 1:8, 1:32, 1:128, and 1:256 (from left to right within each group). No activity was observed with the control Opc⁻ strain MC114 (data not shown).