Bacillus Calmette-Guérin sepsis: shift of an intended local toward a detrimental systemic cytotoxic immune response

A 56-year-old male patient was admitted to our intensive care unit (ICU) because of sepsis with multiple organ failure. Twelve days before admission, the patient underwent adjuvant renal instillation of bacillus Calmette-Guérin (BCG), an attenuated strain ofMycobacterium bovis, after subtotal resection of the right renal pelvis due to papillary transitional cell carcinoma. Bone marrow aspiration revealed multiple epitheloid-cell granulomas with central necrosis, and a positive polymerase chain reaction (PCR) for Mycobacterium tuberculosis complex was found in the tracheobronchial secretion. Diagnosis of BCG sepsis was made. Despite extensive and adequate therapy, multiple organ failure persisted and the patient died after 35 days in the ICU. On autopsy, multiple epitheloid-cell granulomas with central necrosis were found in the spleen, bone marrow, and lungs.

Serial blood samples were collected during the first 5 days in the ICU, in order to evaluate levels of tumor necrosis factor-α (TNF-α), interferon γ (IFN-γ), interleukin-6 (IL-6), IL-8, IL-10, and granzyme A (GrA). Results are given in Table1.

Instillation of BCG is used to enhance the cytotoxic activity by natural killer (NK) cells and cytotoxic T (CTL) cells against transitional cancer cells.1,2 Upon stimulation with BCG, macrophages produce IL-12 and TNF-α, which stimulate NK cells to produce IFN-γ and T cells to differentiate into the T helper type 1 (TH1) subset, then generating IL-2 and IFN-γ. The released IFN-γ potentiates macrophages' microbicidal activity, phagocytosis, oxidative burst capability, and IL-12 production (positive feedback), but in synergy with IL-2 it also activates and enhances cytotoxic properties of NK and CTL cells.3 

In our patient, elevated plasma levels of IL-12, INF-γ, and TNF-α revealed a cytokine pattern typical for activated macrophages and TH1 cells. The concomitant rise in granzyme A in plasma, a specific marker for CTL- and NK-cell activation, strongly suggested enhanced cell-mediated cytotoxicity. The appearance of BCG in the circulation led to a systemic inflammatory response, as reflected by the elevated proinflammatory cytokines IL-6 and IL-8. The anti-inflammatory cytokine IL-10, however, which was reported to play a role in down-regulation of IL-12 production, was hardly detectable in our patient.3 

Upon microbial stimulation, patients with a IL-12 receptor deficiency are unable to generate sufficient amounts of IFN-γ.4Patients with a complete IFN-γ receptor deficiency were reported to suffer from spontaneous recurrent disseminated mycobacterial infections, thereby showing characteristic immature leprosislike granulomas in tissue.5 In contrast, disseminated mature granulomas found in our patient's tissue and elevated levels of IL-12, IFN-γ, TNF-α, and GrA suggest the local cell-mediated cytotoxicity exhibited by macrophages, NK cells, and CTL cells to be sufficient. But systemic release of IL-12, IFN-γ, and TNF-α due to BCG appearance in circulation might have led to a systemic activation and enhancement of cytotoxicity by NK and CTL cells, as reflected by elevated GrA levels. At least in animal models, there is strong evidence that activation of NK cells contributes to the development of multiple organ failure.6 Hence, due to systemic release of IL-12, TNF-α, and IFN-γ, enhanced cytotoxicity elaborated by NK and CTL cells might have been a key step in the development of multiple organ failure in our patient.

Sepsis as a severe but rare complication of BCG-instillation therapy occurs in 0.4% of treated patients.1 We show for the first time that, once in systemic circulation, BCG systemically activates and enhances NK- and CTL-cell–mediated cytotoxicity and, therefore, might contribute to the development of multiple organ failure and, hence, to fatal outcome.

Supported by a grant from the Swiss National Foundation for Scientific Research (no. 32-55312.98) and by an unrestricted grant from Aventis Behring Switzerland.