Serological studies of Actinomyces israelii by crossed immunoelectrophoresis: taxonomic and diagnostic applications.

Crossed immunoelectrophoresis (CIE) with intermediate gel was applied to the serological analysis of Actinomyces israelii to develop a test with high efficiency in the laboratory diagnosis of human actinomycosis and classification of A. israelii. Recently developed standard antigen-antibody systems for A. israelii by CIE were used as reference. The reference systems were based on standard preparations of cytoplasmic and whole cell-associated antigens of A. israelii and a standard immunoglobulin G pool purified from rabbit antisera to formalin-treated whole cells and cell lysates of A. israelii. The specificity of the standard antigens for A. israelii was evaluated in CIE studies by screening for antibodies to components of the antigens in rabbit antisera raised against related bacteria. The standard system for A. israelii based on cytoplasmic antigens formed species-specific precipitins whereas antisera raised against A. naeslundii and/or Propionibacterium acnes precipitated components of the other standard antigens. As a result of these analyses, the standard system for A. israelii based on 10 cytoplasmic antigens was used as reference for CIE studies to detect humoral antibodies to A. israelii in sera from nine patients with actinomycosis. All the sera from the patients formed at the time of diagnosis one or more precipitins in terms of the 10 reference precipitins. Up to five precipitins were found in single sera. Follow-up studies covering a period of one-half year after treatment showed a gradually decreased precipitin response in the course of time. In control sera from patients with newly diagnosed tuberculosis, nocardiosis, deep Candida infection, and aspergillosis, and in sera from healthy blood donors, no antibodies were detected with specificity for the reference antigens.