Monoclonal antibodies against isoelectrically focused Nocardia asteroides proteins characterized by the enzyme-linked immunoelectro-transfer blot method.

Sera from rabbits immunized with culture filtrates and homogenates of Nocardia asteroides B1042 gave at least eight precipitin bands by immunoelectrophoresis. At least 20 proteins with isoelectric points (pls) in the pH 4 to 5.4 range were observed in isoelectric focusing patterns. The enzyme-linked immunoelectro-transfer blot (EITB) assay showed that several of the isofocused proteins reacted with rabbit antisera and with sera from nocardiosis and tuberculosis patients. Antibodies against three proteins with pls of 4, 4.43, and 4.68 (antigenic factors 1,6,8) were present in nocardiosis patients' sera. The proteins were excised from isofocused gels, and IgG monoclonal antibodies (MAbs) were produced by the hybridoma method. MAbs against factors 1 and 6 did not crossreact with cytoplasmic antigens of Mycobacterium chelonae, M. intracellulare serotypes 4B and 8A, M. fortuitum, M. gordonae, or M. kansasii in the EITB method. Factor 8 (MAb) crossreacted with antigens of M. intracellulare and M. fortuitum.