Production and partial characterization of anti-cord factor (trehalose-6,6'-dimycolate) IgG antibody in rabbits recognizing mycolic acid subclasses of Mycobacterium tuberculosis or Mycobacterium avium

An ELISA with cord factor (trehalose-6,6'-dimycolate) is useful for the ser odiagnosis of tuberculosis. To clarify the exact antigenic epitope in cord factor; recognized by a rabbit anti-cord factor IgG antibody, and to ascert ain the most sensitive and specific diagnostic test antigen, rabbits were i mmunized with two kinds of cord factors isolated from Mycobacterium tubercu losis or Myobacterium avium and the reactivities of the sera were tested ag ainst cord factors or the component mycolic acid methyl esters by ELISA. Th e serum from rabbits immunized with M. tuberculosis cord Factor was highly reactive against M. tuberculosis cord factor, but less reactive against M. avium cord factor. In contrast, the serum from rabbits immunized with M. av ium cord factor was highly reactive against M. avium cord factor but less r eactive against M. tuberculosis cord factor. Moreover. the serum from rabbi ts immunized with M. tuberculosis cord factor reacted against mycolic acid methyl eaters, especially methoxy mycolic acid methyl ester. On the other h and, the serum from rabbits immunized with M. tuberculosis cord factor was less reactive against trehalose-6-monomycolate and not reactive against sul folipid (2,3,6,6'-telraacyl trehalose 2'-sulfate). From these results, it w as concluded that the anti-cord factor IgG antibody, produced experimentall y in rabbits, recognized the differences in the cord Factor structures, i.e . the hydrophobic moiety rather than the carbohydrate moiety. It was also n oted that the serum from rabbits immunized with M. tuberculosis cord factor was highly reactive against methoxy mycolic acid as an epitope. This paper is the first to describe how the anti-cord factor IgG antibody can recogni ze the mycolic acid subclasses, which differ according to the species of my cobacteria, (C) 1999 Federation of European Microbiological Societies. Publ ished by Elsevier Science B.V. All rights reserved.