Neutralizing monoclonal antibodies to an extracellular Pseudomonas cepacia protease

Pseudomonas cepacia produces at least two extracellular proteases with apparent molecular masses of 36,000 and 40,000 Da. The 36-kDa protease has high proteolytic activity and the 40-kDa protease has low proteolytic activity with hide powder azure as a substrate. Monoclonal antibodies (MAbs) were raised against the purified 36- and 40-kDa proteases. Several MAbs directed against the 36-kDa protease were found to recognize the 40-kDa protease by Western immunoblot analysis. Similarly, a MAb directed against the 40-kDa protease recognized the 36-kDa protease, suggesting that these two proteases may be immunologically related. A MAb directed against the 36-kDa protease, designated 36-6-8, and a MAb directed against the 40-kDa protease (MAb G-11) cross-reacted with other extracellular proteases, such as Pseudomonas aeruginosa elastase and alkaline protease, Pseudomonas pseudomallei protease, and the Vibrio cholerae hemagglutinin/protease. MAb 36-6-8 neutralized the P. cepacia 36-kDa protease, P. aeruginosa elastase, P. pseudomallei protease, and V. cholerae hemagglutinin/protease but did not affect P. aeruginosa alkaline protease activity. In contrast, MAb G-11 to the 40-kDa protease neutralized only the P. cepacia 36-kDa protease. This evidence suggests that the neutralizing MAb, 36-6-8, recognizes an epitope conserved among some metalloproteases. This epitope may lie at or near the active site of the P. cepacia 36-kDa protease and P. aeruginosa elastase.