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Problems of logistics, compliance and drug resistance point to an urgent need for immunotherapeutic strategies capable of shortening the current 6-month chemotherapy regimens used to treat tuberculosis, or of supplementing ineffective therapy. In this study we sought to define the mechanism of action of two immunotherapies, both of which have previously been shown to prolong survival. Secondly, we wished to identify any clinically useful synergy between these therapies. In BALB/c mice infected via the trachea with Mycobacterium tuberculosis H37Rv there is an initial phase of partial resistance dominated by type 1 cytokines plus tumour necrosis factor-alpha (TNF-alpha) and interleukin-1 (IL-1), followed by a phase of progressive disease. This progressive phase is accompanied by increasing expression of IL-4, and diminished expression of IL-1 and TNF-alpha. Animals in this late progressive phase of the disease (day 60) were treated with two injections (day 60 and day 90) of 0.1 or 1.0 mg of heat-killed Mycobacterium vaccae, or with 3beta, 17beta-androstenediol (AED; 25 microg subcutaneously three times/week), or with both therapies. We show here using four techniques in parallel (morphometry, immunohistochemistry with automated cell counting, semiquantitative reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assays of cytokines in lung extracts) that treatment with M. vaccae causes a switch back towards a type 1 cytokine profile, restoration of expression of IL-1alpha and TNF-alpha, and a switch from pneumonia to granuloma. This is very similar to the changes previously seen after treatment with AED. However, there was no evidence for synergy between M. vaccae and AED.

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BACKGROUND: A third of the world's population has latent infection with Mycobacterium tuberculosis, and in areas of low endemicity, most cases of active tuberculosis arise as a result of reactivation of latent bacilli. We sought to establish the cellular location of these latent organisms to facilitate their elimination. METHODS: We applied in-situ PCR to sections of macroscopically normal lung tissue from 13 individuals from Ethiopia and 34 from Mexico who had died from causes other than tuberculosis. Sections of lung tissue from six Norwegian individuals (ie, individuals from a non-endemic population) acted as negative controls, and six Ethiopian tuberculosis cases acted as positive controls. FINDINGS: Control necropsy samples from the Norwegian individuals were all negative by in-situ PCR and conventional PCR, whereas all samples from known Ethiopian tuberculosis cases were positive by both methods. However, in macroscopically normal lung tissue from Ethiopian and Mexican individuals without tuberculous lesions, the in-situ PCR revealed five of 13 and ten of 34 positive individuals, respectively. These results were confirmed by conventional PCR with extracted DNA. Positive cells included alveolar and interstitial macrophages, type II pneumocytes, endothelial cells, and fibroblasts. INTERPRETATION: M. tuberculosis can persist intracellularly in lung tissue without histological evidence of tuberculous lesions. M. tuberculosis DNA is situated not only in macrophages but also in other non-professional phagocytic cells. These findings contradict the dominant view that latent organisms exist in old classic tuberculous lesions, and have important implications for strategies aimed at the elimination of latent and persistent bacilli.

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Immunity to Mycobacterium tuberculosis requires a T helper 1 (Th1) cytokine balance accompanied by tumour necrosis factor-alpha (TNF-alpha), and activated macrophages. These facets of the immune response are sensitive to suppression by glucocorticoids (GC), which can reactivate and exacerbate tuberculosis in man and animals. Dehydroepiandrosterone (DHEA) and its derivative, 3beta,17beta androstenediol (AED), are reported to have antiglucocorticoid properties in vivo. We therefore investigated the effects of predetermined optimal doses of these compounds, on the course of pulmonary tuberculosis in an established model in BALB/c mice in which an early phase of Th1-mediated response accompanied by adrenal hyperplasia, is followed by a switch to Th2, progressive loss of TNF-alpha expression and disease progression. Both compounds were protective, particularly AED which caused a fall in bacterial counts and prolonged survival. These effects correlated with the appearance within 3 days of cellular infiltrates rich in cells expressing interleukin-2 (IL-2), IL-1alpha and TNF-alpha, and with partial suppression of the switch to IL-4 producing cells that occurred in controls. AED also caused enhanced development of granulomas at 14 days, and persistence of granuloma formation to 120 days, with a corresponding suppression of areas affected by pneumonia. Much of the therapeutic effect of AED and DHEA was obtained by treating for only the first 3 weeks, which is the phase of adrenal hyperplasia. These results suggest that the ratio of GC to anti-GC steroids may play a role in the pathogenesis of tuberculosis, and further investigation could lead to novel treatment strategies.

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When mice were infected with virulent Mycobacterium tuberculosis H37Rv by the intra-tracheal route, there was an early phase of adrenal hyperplasia, histologically resembling the adrenocorticotropic (ACTH)-driven changes seen in Cushing's disease. This was followed at 3 weeks by progressive atrophy until the weight of the adrenals was approximately 50% of that seen in control uninfected mice, in spite of the fact that the adrenals were not infected. All layers of the adrenal cortex were affected, but the medulla was normal. Electron microscope studies revealed apoptosis. The switch from adrenal hyperplasia to adrenal atrophy corresponded to onset of an IgG1 response recognising a wide range of mycobacterial components in Western blots. Delayed type hypersensitivity (DTH) responses were seen throughout, but differed in their sensitivity to TNF alpha. Thus if TNF alpha was injected at 24 h into DTH sites elicited during the phase of adrenal hyperplasia, there was no increment in swelling at 48 h. However similar injections of TNF alpha resulted in a doubling of the swelling in DTH sites elicited during the phase of adrenal atrophy. This may be relevant to the pathogenesis of cytokine-mediated tissue damage in the human disease. If 2 months before mice received the intratracheal infection, they were pre-immunised with 1 x 1097) autoclaved Mycobacterium vaccae, a stimulus previously shown to induce a Th1 pattern of response, the early increase in adrenal weight was attenuated and delayed, and the subsequent atrophy did not occur. In sharp contrast, pre-immunisation with 1 x 10(9) autoclaved M. vaccae, known to prime a mixed pattern of cytokine release (IFN gamma and IL-4), resulted in adrenal atrophy that began within 4 days of infection, and was complete by day 14. These results suggested that the pattern of cytokine release provoked by the infection, modulated the adrenal changes, perhaps in synergy with products derived from the organisms themselves. Since we have already shown that profound adrenal changes also occur in human tuberculosis, we now propose that a change somewhere in the cytokine-hypothalamo-pituitary-adrenal axis may underlie the T cell dysfunction and immunologically-mediated tissue damage in this disease.

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The immune response is impaired in the silent stage of Chagas' disease. We used quadruple skin-testing with new tuberculins in 37 adults who were symptom-free but seropositive for Trypanosoma cruzi and in 37 matched seronegative controls. Whereas 19% of controls responded to common mycobacterial antigens, none of the Chagas' seropositive group responded to them (p < 0.006), demonstrating specificity in their unresponsiveness. The enhanced tuberculin reactivity after BCG vaccination in the control group was suppressed in seropositive subjects (p < 0.002). Selective loss of response to common mycobacterial antigens may have implications for the autoimmune pathology of Chagas' disease, and for susceptibility to tuberculosis, leprosy, and HIV disease.

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A report is given of the use of the enzyme-linked immunosorbent assay to measure antibody to preparations of human thymocyte membranes (HTMA) and to beta 2-microglobulin. The assay described is simple and rapid, and requires only small quantities of an easily stored membrane preparation. The advantages of this technique over conventional methods involving cytotoxicity are discussed. Raised levels of IgM antibody to beta 2-microglobulin were detected in sera from SLE patients. Raised levels of IgG and IgM antibody to HTMA were found in sera from most active lepromatous cases. Two of eight sera from SLE patients showed raised IgG anti-HMTA, but not raised IgM. An attempt was made to study the subclass of the IgG antibodies found, but when checked against purified human IgG myeloma proteins, the available anti-subclass sera were found to lack the necessary degree of specificity in this assay.

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The lymph nodes of mice overloaded with mycobacterial products, either by the injection of whole or ultrasonicated organisms, or as a consequence of severe infection with Mycobacterium ulcerans, contain phagocytic cells which cause spontaneous transformation of the lymph node cells in a low volume, high cell density culture system. This spontaneous mitosis is unaffected by trypsinization but is inhibited by specific antigen and by PHA, and eliminated by treatment with carbonyl iron. Replacement of the macrophages removed with carbonyl iron by a critical number of peritoneal cells, restores the spontaneous transformation. Normal lymph node, thymus or peritoneal lymphocytes will also undergo mitosis if small numbers of peritoneal cells are added to them. This phenomenon therefore appears not to be antigen-dependent, but is probably due to a mediator released from macrophages. The possible role of this phenomenon in the pathogenesis of mycobacterial disease and the 'overloading' of T lymphocytes in vivo is discussed, with reference to similar macrophage-dependent mechanisms reported in other systems.

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