BCG vaccination reduces the mortality of Mycobacterium tuberculosis–infected type 2 diabetes mellitus mice
Rajesh Kumar Radhakrishnan, Ramya Sivangala Thandi, Deepak Tripathi, Padmaja Paidipally, Madeline Kay McAllister, Sachin Mulik, Buka Samten, Ramakrishna Vankayalapati
Rajesh Kumar Radhakrishnan, Ramya Sivangala Thandi, Deepak Tripathi, Padmaja Paidipally, Madeline Kay McAllister, Sachin Mulik, Buka Samten, Ramakrishna Vankayalapati
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Research Article Immunology Infectious disease

BCG vaccination reduces the mortality of Mycobacterium tuberculosis–infected type 2 diabetes mellitus mice

Abstract

Diabetes is a significant risk factor for the development of active tuberculosis. In this study, we used a mouse model of type 2 diabetes mellitus (T2DM) to determine the effect of prior Bacillus Calmette-Guérin (BCG) vaccination on immune responses to Mycobacterium tuberculosis (Mtb) infection. We found that, at 6–7 months after Mtb infection, 90% of the Mtb-infected T2DM mice died, whereas only 50% of BCG-vaccinated T2DM-Mtb–infected mice died. Moreover, 40% of the PBS-treated uninfected T2DM mice and 30% of the uninfected BCG-vaccinated T2DM mice died, whereas all uninfected and infected nondiabetic mice survived. BCG vaccination was less effective in reducing the lung bacterial burden of Mtb-infected T2DM mice compared with Mtb-infected nondiabetic mice. BCG vaccination significantly reduced lung inflammation in Mtb-infected T2DM mice compared with that of unvaccinated T2DM mice infected with Mtb. Furthermore, reduced mortality of BCG-vaccinated Mtb-infected T2DM mice is associated with expansion of IL-13–producing CXCR3+ Tregs in the lungs of Mtb-infected T2DM mice. Recombinant IL-13 and Tregs from BCG-vaccinated Mtb-infected T2DM mice converted proinflammatory M1 macrophages to antiinflammatory M2 macrophages. Our findings suggest a potentially novel role for BCG in preventing excess inflammation and mortality in T2DM mice infected with Mtb.

Authors

Rajesh Kumar Radhakrishnan, Ramya Sivangala Thandi, Deepak Tripathi, Padmaja Paidipally, Madeline Kay McAllister, Sachin Mulik, Buka Samten, Ramakrishna Vankayalapati

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Figure 2

BCG vaccination reduces bacterial burden less efficiently in T2DM mice during chronic infection.

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BCG vaccination reduces bacterial burden less efficiently in T2DM mice d...
PBS control, BCG-vaccinated, T2DM, or BCG-vaccinated T2DM mice were infected with the Mtb as described in Figure 1. (A–C) One and 4 months after Mtb infection, the bacterial burden in the lungs (A), spleen (B), and liver (C) was measured. Experiments were performed 2 times, and each time, 2–3 mice per group were used. The data are shown as mean ± SDs of n = 5 mice per group. The statistical analysis was performed by 1-way ANOVA, followed by Tukey’s multiple comparisons test. *P < 0.05, **P < 0.01, and ***P < 0.001. At 1 and 4 months after infection (p.i.), lungs from uninfected or Mtb-infected mice were isolated and formalin fixed. Paraffin-embedded tissue sections were prepared, and H&E staining was performed. Inflamed lung areas were compared between the groups. (D and E) Representative bright-field microscopic histology images were taken from multiple fields at 20× objective lens. (F and G). The lung inflammation score was assessed at 1 and 4 months p.i. Experiments were performed 2 times, and each time, 2–3 mice per group were used. The data are shown as mean ± SDs of n = 5 mice per group. The statistical analysis was performed by 1-way ANOVA, followed by Tukey’s multiple comparisons test. *P < 0.05, **P < 0.01, and ***P < 0.001.