Immunotherapy for Tuberculosis: Investigative and Practical Aspects

Immunotherapy with Mycobacterium vaccae and peripheral blood flow in long-treated leprosy patients, a randomised, placebo-controlled trial

OBJECTIVE

to evaluate immunotherapy as a means of improving peripheral blood flow in chronic leprosy patients.

DESIGN

this was a double-blind, randomised, placebo-controlled, clinical trial.

MATERIALS

heat-killed Mycobacterium vaccae 1mg plus 0.02 microg Tuberculin protein per 0.1 ml dose in borate buffer, with saline as placebo. Those studied were 92 long-treated residents of a leprosy centre in Iran, 10 of their healthy children and 10 staff members. Evaluation employed the Perimed PF2, Laser-Doppler Flowmeter, a platinum skin thermistor, and a thermal sensibility tester.

METHODS

single intradermal injections of test or placebo were given to 103 patients 18 months before the blinded evaluation. Fingerpulp blood flux was measured in controlled conditions and vasomotor reflexes and skin sensation to touch, pain and heat were evaluated in 45 and 47 patients in the placebo and M. vaccae groups, respectively, and in 20 healthy control persons.

RESULTS

Laser-Doppler flux, skin temperature, vasomotor reflexes and sensation were impaired in leprosy patients. Immunotherapy improved (p < 0.05) Laser-Doppler flux, skin temperature and temperature sensation.

CONCLUSIONS

immunotherapy, given 18 months earlier, significantly improved blood flow and temperature sensation, in fully-treated, chronic, leprosy patients. The same principles might be employed in other conditions of reduced peripheral blood flow.

Increased protection against bovine tuberculosis in the brushtail possum (Trichosurus vulpecula) when BCG is administered with killed Mycobacterium vaccae

SETTING

The Australian brushtail possum is the major wildlife reservoir for Mycobacterium bovis infection in New Zealand. Development of an effective tuberculosis vaccine for possums will reduce the spread of infection to cattle and farmed deer.

OBJECTIVES

To determine whether killed M. vaccae can improve the efficacy of vaccination with M. bovis bacillus Calmette Guerin (BCG) against bovine tuberculosis in the possum.

DESIGN

Groups of possums (n=6-8) were vaccinated via intranasal and intraconjunctival routes with BCG alone or BCG in combination with heat-killed M. vaccae. Controls were non-vaccinated or vaccinated with heat-killed M. vaccae alone. After challenge with virulent M. bovis, protection was assessed by a reduction in loss of body weight and bacterial counts in lungs and spleens. Blood lymphocyte proliferative responses to M. bovis purified protein derivative were monitored throughout.

RESULTS

The earliest lymphocyte responses following vaccination were from animals inoculated with BCG plus 100 microg heat-killed M. vaccae. Loss of body weight was significantly reduced in all BCG-vaccinated groups compared control groups. Spleen bacterial counts were significantly lower in animals vaccinated with M. vaccae plus BCG compared to the non-vaccinated group. Furthermore, vaccination with 100 microg M. vaccae plus BCG significantly reduced spleen bacterial counts compared to vaccination with BCG alone.

CONCLUSION

The possum infection model is one of the first to show that novel vaccine strategies may offer better protection against tuberculosis than BCG alone.

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 11659), 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 Estonia, Iran, Kuwait, New Zealand, Romania, Vietnam and the U.K. A total of 337 patients in the above countries received intradermal injections of M. vaccae in addition to chemotherapy. Patients were grouped according 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 subsequently up to 12 doses at 2-month intervals were given. Chemotherapy varied from isoniazid alone to drugs selected according to susceptibility tests. Most 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 were followed for 18-24 months to exclude relapse. Eighteen of 22 (82%) patients with disease for less than 2 years were bacteriologically cured by one or two doses of M. vaccae. Among 315 chronic patients, 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 died, during the multi-dose regimens. Nine of 33 patients (27%) with advanced disease unaffected by several courses of chemotherapy and discharged on isoniazid alone in Vietnam were cured by 3-12 injections of M. vaccae. The data provide preliminary evidence that the addition of immunotherapy with M. vaccae to chemotherapy improves the rate of cure of MDRTB, most effectively in patients with short histories of disease, but multiple dosing can have beneficial effects in chronic patients in whom chemotherapy has failed. A randomized clinical trial of this immunotherapy in MDRTB patients is therefore required.

The ability of heat-killed Mycobacterium vaccae to stimulate a cytotoxic T-cell response to an unrelated protein is associated with a 65 kilodalton heat-shock protein

Exogenous antigens are generally presented by Class II major histocompatibility (MHC) molecules. When administered with an adjuvant, however, they are capable of inducing a CD8+ T-cell response where antigen recognition is associated with Class I MHC. Accordingly, immunization with soluble ovalbumin (OVA) alone does not activate CD8+ cytotoxic T cells (CTL) but when given in complete Freund's adjuvant (CFA), or in formulations of a number of novel adjuvants, an OVA-specific CD8+ CTL response can be detected. We show in this report that immunization with soluble OVA mixed with heat-killed Mycobacterium vaccae, but not with other common pathogenic and saprophytic mycobacteria, can activate OVA-specific CD8+ CTL. An OVA-specific CTL response is detected when mice are immunized by either the intraperitoneal or intranasal route and their spleen cells are re-stimulated in vitro. Adjuvant activity of heat-killed M. vaccae is present in M. vaccae culture filtrate, in soluble protein components of whole M. vaccae and in the 65 kDa heat-shock protein (hsp) of M. vaccae. Mycobacterium vaccae has previously been shown to have no adverse side-effects in humans. The current results suggest that M. vaccae may be useful as an adjuvant for vaccines and other immunotherapies where CD8+ CTL responses to exogenous proteins are crucial.

Clinical trials of immunotherapy for advanced prostate cancer

There is a lack of effective therapeutic regimens for advanced hormone-refractory prostate cancer (HRPC). Recent combination regimens of chemotherapy have improved management of HRPC. Neither systemic chemotherapy nor radiation regimens have significantly improved survival. Conventional systemic cytokine therapy has had limited efficacy in the treatment of advanced prostate cancer patients and its toxicity is severe. Combinations of multiple biological response modifiers for treatment of this disease also have limited efficacy. Results from phase II trials have shown that the combination of interferon-alpha and interleukin-2 therapy and the infusion of dendritic cells primed with peptides of prostate specific membrane antigen are promising. The former showed 31% response using the National Prostatic Cancer Project criteria, and the latter showed 27% of objective partial response with a reduction of >50% prostate specific antigen level. The toxicity of these two regimens was tolerated by patients. New approaches with tumor vaccines in conjunction with cytokine gene therapy have also been investigated. The clinical responses of these trials have been limited but promising. Immunotherapy may become an effective modality of prostate cancer treatment in the future.

Double-blind placebo-controlled trial of Mycobacterium vaccae immunotherapy for tuberculosis in KwaZulu, South Africa, 1991-97

To investigate Mycobacterium vaccae immunotherapy in the treatment of human tuberculosis and to assess longer-term outcomes following treatment for tuberculosis patients, a double-blind placebo-controlled Phase-2 clinical trial was set up in the Mseleni and Manguzi health wards in north-eastern KwaZulu, South Africa. In 1991-93, 204 patients admitted with clinical tuberculosis to the 2 hospitals were allocated to receive single intradermal doses of 0.1 mL M. vaccae NCTC 11659 or 0.1 mL tetanus toxoid alongside standard 6-months chemotherapy with rifampicin, isoniazid, pyrazinamide and ethambutol. The main outcome measures were sputum bacteriology culture conversion to negativity, clinical assessment, weight gain, erythrocyte sedimentation rate and chest radiography. Patients were followed-up after 4 years to determine their health status. M. vaccae cases gained weight more quickly during the first 8 weeks compared with 'placebo' patients. Regression analysis found a synergistic relationship between BCG positive scar status and M. vaccae-induced weight gain. No further difference was found between treatment groups. The bacterial conversion rate to negativity at 2 months was much lower than expected (44.8% active, 38.8% placebo). Mortality was considerably higher than expected after treatment (7.1% each group) and after 4 years (25.8% active, 21.0% placebo; death from tuberculosis 14.5% and 16.1%, respectively). Immune sensitization to environmental mycobacteria may explain the geographical variability of M. vaccae efficacy, as occurs with BCG vaccination and occurred with Koch's tuberculins of the late 19th century. Multiple doses of M. vaccae may be more effective. Further work is required to link the ability of M. vaccae to modulate protective cytokine profiles to favourable outcome in clinical studies. The high mortality found in this study suggests urgent reviews of chemotherapy and monitoring of patients are necessary in KwaZulu.

Mycobacterium vaccae (SRL172): a potential immunological adjuvant evaluated in rat prostate cancer

OBJECTIVE

To evaluate the potential of heat-killed Mycobacterium vaccae (SRL172) as a nonspecific immunostimulant and as an adjuvant to whole tumour cell vaccination in the rat model of prostate cancer.

MATERIALS AND METHODS

SRL172 was used as a vaccine in the prevention and treatment of subcutaneous tumours in rats. Prevention experiments were conducted using subcutaneous MAT-LyLu tumours in Copenhagen rats, comparing vaccination with SRL172 alone, SRL172 plus autologous cells, and bacille Calmette-Guèrin (BCG) plus autologous cells before tumour implantation. Treatment experiments were conducted using subcutaneous MAT-LyLu tumours in the Copenhagen rat and subcutaneous PAIII tumours in the Lobund-Wistar rat. Tumours were induced by subcutaneous injection with tumour cells. Animals were then vaccinated with autologous cells, autologous cells plus SRL172, or SRL172 alone.

RESULTS

SRL172 was effective as an adjuvant to autologous whole tumour cell vaccination in the prevention of MAT-LyLu tumours and the survival benefit was equivalent to that provided when the adjuvant was live-attenuated BCG. SRL172 alone did not reduce tumour take or tumour growth in this model and neither strategy was effective in delaying the growth of established MAT-LyLu tumours. In the Lobund-Wistar rat vaccination with autologous whole tumour cells and SRL172 significantly delayed the growth of established tumours.

CONCLUSION

Mycobacterium vaccae deserves further evaluation as an adjuvant to whole tumour cell vaccination in a phase I clinical trial in patients with prostate cancer.

Pulmonary bovine-type tuberculosis in rabbits: bacillary virulence, inhaled dose effects, tuberculin sensitivity, and Mycobacterium vaccae immunotherapy

This report elucidates four aspects of the immunology of pulmonary tuberculosis produced in rabbits: (i) the virulence of bovine-type tubercle bacilli, strain Ravenel S, (ii) systemic factors influencing the generation of visible primary pulmonary tubercles, (iii) differences in tuberculin sensitivity of rabbits and humans, and (iv) the effect of Mycobacterium vaccae immunotherapy on cavitary tuberculosis. Laboratory strain Ravenel S (ATCC 35720) was not fully virulent. Fully virulent strains produce one visible primary pulmonary tubercle for each three bacillary units inhaled. Strain ATCC 35720 produced one such tubercle for each 18 to 107 bacillary units inhaled, indicating that its virulence was reduced by 6- to 36-fold. When a low dose of this Ravenel S strain was inhaled, the host resistance (measured by the number of inhaled bacilli needed to generate one visible primary pulmonary tubercle) was increased at least 3.5-fold compared to the host resistance when a high dose was inhaled. Rabbits and humans differ in the degree and in the maintenance of their dermal sensitivities to tuberculin. Compared to rabbits, humans are 100 times more sensitive to tuberculin. Also, at 33 weeks rabbits with well-controlled cavitary tuberculosis usually showed a decrease in their tuberculin reactions of about 50% from peak values, whereas humans with such well-controlled tuberculosis are thought to maintain strong reactions for many years. These species differences may be due to desensitization to group II mycobacterial antigens in the rabbits because they have a different diet and a different type of digestive tract. M. vaccae immunotherapy of rabbits with cavitary tuberculosis produced no statistically significant effects. Experiments with many more rabbits would be required to prove whether or not such immunotherapy is beneficial.

Immunotherapy of advanced prostate cancer: a phase I/II trial using Mycobacterium vaccae (SRL172)

OBJECTIVE

To assess whether a new heat-killed Mycobacterium vaccae preparation (SRL172), which enhances cell-mediated immunity and has been proposed for use as an immunotherapeutic agent against cancer, is safe in patients with advanced hormone-refractory prostate cancer, can stimulate desirable cytokine changes in these patients and modulate the progression of the disease.

PATIENTS AND METHODS

Ten patients were given SRL172 intradermally at regular intervals. The serum prostate specific antigen (PSA) level was used as a surrogate marker of response. The proportion of peripheral blood mononuclear cells (PBMC) secreting interleukin 2 (IL2), interferon gamma (IFNgamma) and interleukin 4 (IL4) was measured by flow cytometry (FACS) before and after vaccination to assess whether the treatment induced a Th2 (predominantly humoral) to Th1 (predominantly cell-mediated) switch.

RESULTS

There were no significant adverse events. In five patients the serum PSA declined during the trial and in two of these there was no concomitant change of therapy apart from vaccination with SRL172. Before vaccination with SRL172 patients had a low proportion of PBMC producing IFNgamma and IL2 (all 10) and a higher proportion secreting IL4 (all three tested), suggesting a predominantly Th2 cytokine profile. After vaccination the proportion of IL4 secreting PBMC fell in all three patients tested. The proportion of IL2 secreting PBMC increased in three patients whose PSA fell. The proportion of IFNgamma-secreting cells remained depressed in nine of 10 patients.

CONCLUSION

Two patients with advanced hormone-refractory prostate cancer had a PSA response to the vaccination with SRL172. The proportion of PBMC secreting IL2 is a potential marker of response to immunotherapy.

Studies of vaccination of persons in close contact with leprosy patients in Argentina

A total of 670 adults living or working with leprosy patients, were examined for a BCG vaccination scar, and skin-tested with four new tuberculins. Based on the results 513 were vaccinated, 65 with Bacille de Calmette et Guérin (BCG) alone, 66 with BCG plus killed Mycobacterium vaccae and 382 with killed M. vaccae alone. Skin-testing was repeated 2-3 years later on 344 subjects, when all three vaccines were found to have been highly successful in increasing responses to Tuberculin and Leprosin A (p < 0.0005) with increased immune recognition of common and species-specific antigens. Mean diameters of induration to each skin-test were greatest in recipients of BCG alone (p < 0.05), which suggests that better immuno-regulation occurs after receiving vaccines that incorporate M. vaccae. The results suggest 10(8) M. vaccae alone might prove a valuable future vaccine, which would not require selective pre-vaccination procedures.

Immunization with heat-killed Mycobacterium vaccae stimulates CD8+ cytotoxic T cells specific for macrophages infected with Mycobacterium tuberculosis

Immune responses to Mycobacterium tuberculosis are analyzed in mice which have been immunized with Mycobacterium vaccae to examine novel ways of altering protective immunity against M. tuberculosis. The spleen cells of mice immunized with M. vaccae proliferate and secrete gamma interferon (IFN-gamma) in response to challenge with live M. tuberculosis in vitro. Immunization with M. vaccae results in the generation of CD8+ T cells which kill syngeneic macrophages infected with M. tuberculosis. These effector cytotoxic T cells (CTL) are detectable in the spleen at 2 weeks after immunization with M. vaccae but cannot be found in splenocytes 3 to 6 weeks postimmunization. However, M. tuberculosis-specific CTL are revealed following restimulation in vitro with heat-killed M. vaccae or M. tuberculosis, consistent with the activation of memory cells. These CD8+ T cells secrete IFN-gamma and enhance the production of interleukin 12 when cocultured with M. tuberculosis-infected macrophages. It is suggested that CD8+ T cells with a cytokine secretion profile of the Tc1 class may themselves maintain the dominance of a Th1-type cytokine response following immunization with M. vaccae. Heat-killed M. vaccae deserves attention as an alternative to attenuated live mycobacterial vaccines.

MULTIDRUG RESISTANT TUBERCULOSIS - BIOMECHANISM, EPIDEMIOLOGY AND MANAGEMENT STRATEGIES

Muitidrug resistant tuberculosis has shown an alarming increase and this assumes added importance in view of the increasing number of HIV infected patients. This article reviews the biomechanism of resistance and discusses the present stategies that are available and recommended to tackle the rising incidence of tuberculosis due to resistant mycobacteria.

Immunotherapy with Mycobacterium vaccae in the treatment of tuberculosis in Romania. 1. Newly-diagnosed pulmonary disease

In this study, 206 previously untreated patients with sputum culture positive pulmonary tuberculosis were randomized to receive an injection of killed Mycobacterium vaccae as immunotherapy, or of saline as placebo, after 1 month of a 6-month chemotherapeutic regime. Not surprisingly in a disease for which there is good chemotherapy, the difference in numbers which were culture negative at the end of treatment was small, and the final outcome at the latest post-treatment follow-up did not reach statistical significance between the two arms of the study. Nonetheless, those receiving immunotherapy showed better progression in every parameter measured, suggesting faster and more complete cure. Whereas seven of 97 patients receiving immunotherapy required a course of re-treatment and five still had active disease after a mean follow-up of 2 yr, 13 of 109 placebo recipients required re-treatment and nine still had active disease at the end of the study. Only one patient receiving M. vaccae plus chemotherapy died of tuberculosis, compared with four of those receiving chemotherapy alone. A degree of drug resistance was shown by the bacilli cultured from 25 of 175 (14%) patients, and seven of them (4.0%) were multi-drug resistant. Fourteen patients received immunotherapy of whom 13 were cured, including all three of those showing multi-drug resistance. Of the 11 patients with drug resistance in the control group, eight were cured, and one patient with multi-drug-resistant disease died of tuberculosis during re-treatment.

Immunotherapy with Mycobacterium vaccae in the treatment of tuberculosis in Romania. 2. Chronic or relapsed disease

In this study of 102 patients with culture-positive chronic treatment failure or repeatedly relapsed pulmonary tuberculosis receiving chemotherapy, 56 received an injection of killed Mycobacterium vaccae as immunotherapy after 1 month of treatment. At the start of treatment, there was little difference between those receiving immunotherapy and the 46 patients in the control group receiving chemotherapy alone. Thereafter, the two groups diverged so that 1 yr later, 43 of 56 (77%) patients receiving M. vaccae had a successful outcome, in comparison with 24 of 46 (52%) patients receiving chemotherapy alone (P < 0.02). Successful results were obtained from patients infected with drug-resistant bacilli, 20 of 32 (63%) patients compared with 11 of 25 (44%) patients, respectively, as well as from fully drug-sensitive cases (23 of 24 compared with 12 of 21 patients; P = 0.004). At the final follow-up after 22 months, 13 of 56 patients receiving immunotherapy had an unfavourable outcome compared with 26 of 46 members of the control group (P = 0.0006). During the study, 16 patients died of tuberculosis (six after immunotherapy), and 12 were lost to follow-up. Not only was bacteriological success improved by immunotherapy, chest X-ray showed markedly better resolution of cavities and other radiological lesions, recovery of body weight was improved, and the mean erythrocyte sedimentation rate returned almost to normal (P < 0.001) in comparison with those receiving chemotherapy alone. These changes were seen even in those failing bacteriological cure, suggesting that the immunotherapy had been effective, but that bacilli were replicating in an extracellular situation, protecting them from its effects.