Improved immunotherapy for pulmonary tuberculosis with Mycobacterium vaccae

We previously demonstrated that a single intradermal injection of 10⁹ irradiation-killed M. vaccae, given 1 month after starting chemotherapy, caused significant changes in responses to mycobacterial antigens. Amongst 38 patients with pulmonary tuberculosis, 29% had lymphocytes responding to common mycobacterial antigens after the injection, compared with only 11 % of 49 similar patients after an injection of saline (p < 0.03).

To increase the proportion of responders to these antigens, six modifications of the potentially immunotherapeutic injection, randomized with injections of saline, have been assessed by biochemical, clinical, haematological, immunological and radiological criteria.

Subsequent lymphocyte proliferation to mycobacterial antigens enabled the modifications to be ranked in order of efficacy. Tuberculin plus murabutide plus 10⁹ irradiated M. vaccae (36% of 25), an autoclaved preparation of 10⁹M. vaccae (45% of 22), and 2 x 10⁹ irradiated M. vaccae (75% of 12) were the most effective. Antibody responses in several IgG subclasses to mycobacteria, but not streptococci, were also significantly increased by the most effective modifications over the 8 weeks following injection.

Detailed radiological study showed that use of the autoclaved bacilli was followed by a delay in clearing of consolidation, but by better closing of cavities than was found in the control group, suggesting enhanced, or altered, immunological activity around the lesions.