cord-factors and Mycobacterium-avium-intracellulare-Infection

The detection of anti-cord factor (trehalose 6,6'-dimycolate) IgG antibody in active (smear-and/or culture-positive) and inactive (smear-and culture-negative) tuberculosis patients is a useful serodiagnostic tool that can be used for early clinical diagnosis of the disease. We estimated the titers of anticord factor IgG antibody in the sera of tuberculosis patients, and compared them with those of Mycobacterium avium-infected patients. Most of the serum samples obtained from the tuberculosis patients were highly reactive against M. tuberculosis (MTB) cord factor isolated from M. tuberculosis H37Rv, a human-type mycobacterial strain, whereas they were less reactive against M. avium (MAC) cord factor. Similarly, most of the serum samples of the MAC-infected patients were highly reactive against MAC cord factor and less reactive against MTB cord factor. These results suggest that anti-cord factor IgG antibody recognizes the mycolic acid subclasses as an epitope which comprises cord factor, since MTB and MAC cord factor differ in mycolic acid subclasses and molecular species composition. To clarify the exact antigenic epitope in cord factor and to find out a more sensitive and specific diagnostic test antigen, we examined the reactivity of patients' sera to glycolipids containing trehalose (cord factor and sulfolipid) obtained from various mycobacterial species. Furthermore, the reactivity of human antisera to various mycolic acid subclasses (alpha-, methoxy and keto mycolic acids) of MTB cord factor was compared. We found that anti-cord factor IgG antibody in the sera of human tuberculosis patients most strikingly recognized methoxy mycolic acid in the cord factor of M. tuberculosis, whereas it recognized alpha- and keto mycolic acids weakly. Pre-absorption studies of antibody with MTB cord factor or methoxy mycolic acid methyl ester showed that anti-cord factor antibody was absorbed partially, but consistently. This is the first report describing that the specific subclass of mycolic acid from mycobacteria is antigenic in the humoral immune system of human tuberculosis infection.

Topics: Antibodies, Bacterial; Antigens, Bacterial; Cord Factors; Enzyme-Linked Immunosorbent Assay; Epitopes; Glycolipids; Humans; Immunoglobulin G; Mycobacterium avium Complex; Mycobacterium avium-intracellulare Infection; Mycobacterium tuberculosis; Mycolic Acids; Tuberculosis, Pulmonary

Mycobacterium avium-intracellulare complex (MAC) is one of the most important opportunistic pathogens, particularly in patients with acquired immunodeficiency syndrome (AIDS). The aim of this study was to determine whether an enzyme-linked immunosorbent assay (ELISA) using trehalose 6,6'-dimycolate (TDM) as an antigen can be used for the rapid serodiagnosis of MAC infection. We also identified MAC serotypes by ELISA using serotype-specific glycopeptidolipid (GPL) antigen. To confirm our findings, the thin-layer chromatographic (TLC) behavior of serotype-specific GPL of the strains isolated from MAC-infected patients was also tested. Forty patients infected with MAC and 30 healthy controls were tested. Thirty-two of the 40 MAC-infected patients had higher titers of serum antibodies against MAC TDM than against MTB TDM, while all 30 healthy control sera were unreactive to MAC TDM and MTB TDM. Results of the GPL ELISA indicated that 20 of the 40 MAC-infected patients' sera were reactive against serotype 4 GPL, 3 against serotype 8 GPL, and 1 against serotype 16 GPL. A TLC analysis of the GPL of the 40 MAC isolates showed that 16 strains were of serotype 4, 5 of serotype 8, and 2 of serotype 16. Results of the GPL ELISA were in good accord with those of the TLC analysis for most patients. Our findings suggest that ELISA using TDM is useful for rapid serodiagnosis of MAC infection, and that complementary ELISA testing using serotype-specific GPL gives additional detailed information concerning MAC serotypes.

Topics: Adult; Aged; Aged, 80 and over; Antigens, Bacterial; Chromatography, Thin Layer; Cord Factors; Enzyme-Linked Immunosorbent Assay; Female; Glycolipids; Glycopeptides; Humans; Male; Middle Aged; Mycobacterium avium Complex; Mycobacterium avium-intracellulare Infection; Serologic Tests; Serotyping; Time Factors