Clinical usefulness of serological measurements obtained by antigen 60 in mycobacterial infections: development of a new concept

The humoral immune response occurring during mycobacterial infections was analysed with an ELISA test based on antigen 60. With tuberculosis, IgM antibodies indicate a primo-infection or a process of reactivation while IgG determinations allow an evaluation of the intensity of the infectious process. The test is also applicable to extrapulmonary tuberculosis, provided its sensitivity be adapted to these particular cases. This is particularly clear for tuberculous meningitis. The test is not species-specific and allows the detection of antibodies in atypical mycobacterioses and in leprosy patients. The final differentiation must be done by clinical examinations and cultures. In leprosy patients, IgM antibodies are detected nearly as frequently as IgG antibodies. In HIV-seropositive patients, the A60 seropositivity is correlated with a reactivation of former tuberculous infections and with primary tuberculous infections. At the AIDS stage, the A-60 seropositivity is due to atypical mycobacteria, with a better IgM than IgG response. Healthy people are negative in serology: the positive cases observed are due to inapparent infections gained by contact with an infectious focus. The seropositive cases observed in non-tuberculous hospitalized patients are restricted to some disease types, essentially lung infections (cystic fibrosis, cancer pneumopathies, sarcoidosis). Some patients have low levels of antibodies. This anergy may be traced to the formation of immune complexes or else to a weak avidity of the specific antibodies produced. This test should not be considered to be a diagnostic tool by itself. It should be used in conjunction with other diagnostic means that, together, allow the determination of a diagnosis.

ELISA serodiagnosis of Johne's disease in cattle

An ELISA test for the serodiagnosis of M. paratuberculosis in cattle has been developed. The test is based on antigen 60 from BCG. It is specific for myocobacteria and detects M. bovis and M. paratuberculosis antibodies. The correlation between sero-units and complement fixation is not an absolute one. On the basis of these preliminary results, a cut-off established at an optical density (OD) of 0.42-0.45 when the sera are analysed at a 1:100 dilution, corresponding to 200 serounits, seems to be adequate. The greatest usefulness of the test appears to consist in the exclusion of a presumed mycobacterial infection.

Development of an enzyme immunoassay for the serodiagnostic of tuberculosis and mycobacterioses

An enzyme-linked immunosorbent assay (ELISA) test has been developed for the serodiagnosis of mycobacterioses. The test is based on an interspecific antigen, antigen 60 (A60). This antigen belongs to the group of thermostable macromolecular antigens and is the principal constituent of tuberculin RT 23. A60 is composed of proteins, polysaccharides and lipids in a ratio that varies with the growth cycle of the mycobacterium. The test detects antibodies against mycobacteria and is most effective in cases of active infections. We found that the best way to cope with the day-to-day variations in the results obtained was to transform the absorbance values into arbitrary IgG units. The variations observed with IgM antisera were, however, too great to allow more than a qualitative test. Healthy individuals are negative in the IgG and IgM tests and tuberculous patients are usually positive in the IgG test. The presence of IgM antibodies was only rarely observed. For IgG antibodies, the best discriminative power at a 1:100 dilution of the analyzed sera seemed to lie at 125 sero-units. It was found that some sera originating from clinically documented tuberculous cases responded in a poor way in this test.

Incidence of inapparent active mycobacterial infections in France detected by an IgG serological test based on antigen 60

A serological test detecting circulating mycobacterial antibodies of the IgG type applied to various populations. The test detected no positive cases among old age people in a retirement home. Among sexually active women, 3% were positive. This percentage of antigen 60-positive cases was also found among asymptomatic HIV seropositives. The percentage augmented to 5.7% when hospital attendants were analyzed and augmented further to 14% when people known to have had contact with a man suffering from pulmonary tuberculosis were analyzed.

Nocturnal asthma: slow-release terbutaline versus slow-release theophylline therapy

In a double-blind cross-over study, the effects of slow release (S-R) terbutaline tablets (b.i.d. 0.25 mg/kg per day) and S-R theophylline (5.31 mg/kg morning and 10.62 mg/kg evening) were compared in eleven patients with nocturnal asthma. On day seven of each treatment period, drug serum concentrations and peak expiratory flow (PEF) were measured every 2h over a 24-h period. During daytime, terbutaline concentrations ranged from 1.6-14.1 (median 4.5) microgram/l and during the night from 2.1-18.7 (median 4.9) micron/l. Theophylline concentrations ranged from 3.9-24.3 (median 11.5) mg/l during the day and from 3.3-20.9 (median 10.4) mg/l at night. Nocturnal wheezing occurred during theophylline treatment in four patients 7 times and during terbutaline treatment in six patients 22 times. Daytime PEF values were 472 +/- 161 l/min during theophylline therapy versus 445 +/- 169 l/min during terbutaline therapy (p less than 0.05). In the night and early morning there was no significant difference between PEF values with the two treatment forms. During theophylline treatment, fewer inhalations of beta 2-sympathomimetics were used, and there were fewer side effects. One patient experienced severe asthmatic attacks during the terbutaline treatment period. The patients preferred theophylline for the treatment of nocturnal asthma.

Nocturnal asthma: slow-release terbutaline versus slow-release theophylline therapy

In a double-blind cross-over study, the effects of slow release (S-R) terbutaline tablets (b.i.d. 0.25 mg/kg per day) and S-R theophylline (5.31 mg/kg morning and 10.62 mg/kg evening) were compared in eleven patients with nocturnal asthma. On day seven of each treatment period, drug serum concentrations and peak expiratory flow (PEF) were measured every 2h over a 24-h period. During daytime, terbutaline concentrations ranged from 1.6-14.1 (median 4.5) microgram/l and during the night from 2.1-18.7 (median 4.9) micron/l. Theophylline concentrations ranged from 3.9-24.3 (median 11.5) mg/l during the day and from 3.3-20.9 (median 10.4) mg/l at night. Nocturnal wheezing occurred during theophylline treatment in four patients 7 times and during terbutaline treatment in six patients 22 times. Daytime PEF values were 472 +/- 161 l/min during theophylline therapy versus 445 +/- 169 l/min during terbutaline therapy (p less than 0.05). In the night and early morning there was no significant difference between PEF values with the two treatment forms. During theophylline treatment, fewer inhalations of beta 2-sympathomimetics were used, and there were fewer side effects. One patient experienced severe asthmatic attacks during the terbutaline treatment period. The patients preferred theophylline for the treatment of nocturnal asthma.