Does immunotherapy with heat-killed Mycobacterium vaccae, offer hope for the treatment of multi-drug-resistant pulmonary tuberculosis?

The ability of immunotherapy with heat-killed Mycobacterium vaccae (NCTC 11 659), as an addition to the available chemotherapy, to improve the outcome in patients with multi-drug-resistant tubercle bacilli (MDRTB) who had not been cured by chemotherapy alone was evaluated in tuberculosis centres in E stonia, Iran, Kuwait, New Zealand, Romania, Vietnam and the U.K. A total of 337 patients in the above countries received intradermal injecti ons of M. vaccae in addition to chemotherapy. Patients were grouped accordi ng to the length of their histories of disease: less than or greater than 2 years duration. Initially, single doses of M. vaccae were given but subseq uently up to 12 doses at 2-month intervals were given. Chemotherapy varied from isoniazid alone to drugs selected according to susceptibility tests. M ost patients had failed to respond to repeated courses of chemotherapy and the majority were expected to die from their disease. Results were assessed by sputum smear and culture and by clinical observations. Cured patients w ere followed for 15-24 months to exclude relapse. Eighteen of 22 (82%) patients with disease for less than 2 years were bacte riologically cured by one or two doses of M. vaccae. Among 315 chronic pati ents, 24 (7.6%) were cured after one dose, 37.9% after seven doses and 41.6 % after 12 doses. Sixty-six chronic patients were lost to follow-up, or die d, during the multi-dose regimens. Nine of 33 patients (27%) with advanced disease unaffected by several courses of chemotherapy and discharged on iso niazid alone in Vietnam were cured by 3-12 injections of M, vaccae. The data provide preliminary evidence that the addition of immunotherapy wi th M, vaccae to chemotherapy improves the rate of cure of MDRTB, most effec tively in patients with short histories of disease, but: multiple dosing ca n have beneficial effects in chronic patients in whom chemotherapy has fail ed. A randomized clinical trial of this immunotherapy in MDRTB patients is therefore required. (C) 2001 HARCOURT PUBLISHERS LTD.