Interactions between hormone‐mediated and vaccine‐mediated immunotherapy for pulmonary tuberculosis in BALB/c mice

Abstract

SUMMARYProblems 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 de®ne 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-a (TNF-a) 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-a. 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 3b,17b-androstenediol (AED; 25 mg 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 pro®le, restoration of expression of IL-1a and TNF-a, 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.

Do successful tuberculosis vaccines need to be immunoregulatory rather than merely Th1-boosting?

“…(The findings of Robert Koch in the 1890's are rediscovered at regular intervals). Interestingly the only vaccine candidates shown to be effective therapeutically in the Balb/c mouse TB model both work at least in part by 9 suppressing the IL-4 response [34,35], which BCG, studied in parallel, failed to do [35]. In conclusion the time may have come for a radical reappraisal of the thinking behind the current wave of "rationally" designed vaccine candidates.…”

Immunological and pathological comparative analysis between experimental latent tuberculous infection and progressive pulmonary tuberculosis

“…Sections 5 mm thick taken through the hilus were stained with haematoxylin and eosin. In these slides, the area (mm 2 ) occupied by the inflammatory infiltrate in the alveolarcapillary interstitium, bronchial and venules wall, as well as granulomas, and the percentage of lung surface affected by pneumonia, was determined using an automated image analyser (Q Win Leica, Milton Keynes, UK) [11].…”

“…For quantification, five random fields of each pulmonary lobe in two different experiments, each of eight mice, were evaluated at ¥200 magnification. Immunohistochemical positive and negative cells located in granulomas and pneumonic or alveolitis areas were counted by a computerized image analyser (Q Win Leica) and the data expressed as percentage of positive cells [11].…”

“…Four dilutions of each homogenate were spread onto duplicate plates containing Bacto Middlebrook 7H10 agar (Difco, Detroit, MI, USA) enriched with oleic acid, albumin, dextrose, catalase. The time for incubation and colony counting was 21 days [11].…”

M. tuberculosis: immunology and vaccination

“…from 28 days after initiating immunotherapy (pv0.01)). Adapted from [216]. DOTS, there is a clear need for a trial of multiple doses in multidrug resistant disease, as used in the pilot non-GCP studies in multidrug resistant TB [222].…”