Longitudinal Trends in Serum Levels of Mycobacterial Secretory (30 kD) and Cytoplasmic (65 kD) Antigens During Chemotherapy of Pulmonary Tuberculosis Patients

Antigen 85 (mol. wt 30,000) (30 kD), secreted by actively growing mycobacteria under axenic conditions, and mol. wt 65,000 (65 kD), a cytoplasmic antigen released during mycobacterial lysis, were used to monitor the efficacy of chemotherapy in previously untreated pulmonary tuberculosis (UPTB) patients using enzyme-linked immunosorbent assay. Sera from 125 UPTB patients were examined for each of the 2 antigens individually and for the ratio of secretory (30 kD) to cytoplasmic (65 kD) antigen (SCR), before commencement of treatment, after intensive phase (IP), completion of optimum period of treatment (COPT) and 6 months post-COPT. 116 controls (normals and contacts) were also checked for these antigens. The detection of 30 kD and 65 kD antigens in UPTB patients had a sensitivity ranging from 50-57% (mean 30 kD value: 0.64 +/- 1.24 ngs/ml) to 20-22% (mean 65 kD value: 0.51 +/- 1.87 ngs/ml), respectively, whereas in controls it ranged from 2-8% (0.05 +/- 0.28 ngs/ml) to 14-47% (0.09 +/- 0.22 ngs/ml), respectively. Although the decline in 30 kD positivity was more evident at COPT, computation of the SCR denoted efficacy of chemotherapy more readily at IP. Similarly, SCR resolved the ambiguity between individual antigen levels and the clinical status of a patient. Since significant numbers of patients demonstrated 30 kD at IP it may be computed that the lifespan of circulating 30 kD in serum could be at least 2 months after the start of treatment, declining gradually thereafter. Although seromonitoring for secretory antigen generally reflects the efficacy of chemotherapy, the interpretation of findings clearly requires further elucidation.