Guanylate binding proteins contained in the murine chromosome 3 are important to control mycobacterial infection

Abstract

Guanylate binding proteins (GBPs) are important effector molecules of autonomous response induced by proinflammatory stimuli, mainly IFNs. The murine GBPs clustered in chromosome 3 (GBPchr3) contains the majority of human homologous GBPs. Despite intense efforts, mycobacterial-promoted diseases are still a major public health problem. However, the combined importance of GBPchr3 during mycobacterial infection has been overlooked. This study addresses the influence of the GBPchr3 in host immunity against mycobacterial infection to elucidate the relationship between cell-intrinsic immunity and triggering of an efficient antimycobacterial immune response. Here we show that all GBPchr3 are up-regulated in lungs of mice during Mycobacterium bovis BCG infection, resembling tissue expression of IFN-. Mice deficient in GBPchr3 (GBPchr3 −/−) were more susceptible to infection, displaying diminished expression of autophagy-related genes (LC3B, ULK1, and ATG5) in lungs. Additionally, there was reduced proinflammatory cytokine production complementary to diminished numbers of myeloid cells in spleens of GBPchr3 −/−. Higher bacterial burden in GBPchr3 −/− animals correlated with increased number of tissue granulomas. Furthermore, absence of GBPchr3 hampered activation and production of TNF-and IL-12 by dendritic cells. Concerning macrophages, lack of GBPs impaired their antimicrobial function, diminishing autophagy induction and intracellular killing efficiency. In contrast, single GBP2 deficiency did not contribute to in vivo bacterial control. In conclusion, this study shows that GBPchr3 are important not only to stimulate cell-intrinsic immunity but also for inducing an efficient immune response to control mycobacterial infection in vivo.

Mycobacterium tuberculosisevasion of Guanylate Binding Protein-mediated host defense in mice requires the ESX1 secretion system

“…Understanding the immune mechanisms that restrict the intracellular growth of Mtb is essential for the rational design of interventions. Initial observations demonstrating a role for GBPs in the control of BCG growth suggested that this pathway might represent an important component of IFNg -mediated immunity to Mtb (22,23). However, while we were able detect the previously-described role for the chromosome 3 GBPs in immunity to BCG, we found that these proteins have no effect during Mtb infection.…”

“…The increased susceptibility of IFNgR -/compared to Gbp chr3-/mice indicated that the function of these GBPs accounted for some but not all of the protective effect of IFNg. Together these data show that the GBPs on chromosome 3 are able to restrict the growth of BCG in IFNg -stimulated macrophages and in the intact animal, which is consistent with the previously described roles of GBPs in immunity to BCG (22,23).…”

“…Similarly, mice lacking GBP1 or the cluster of 5 GBP proteins on chromosome 3 are more susceptible to intravenous BCG challenge (22,23). While the mechanism of BCG control remains unclear, GBPs are known to bind to pathogen containing vacuoles in other infections and recruit additional effector molecules (17,24).…”

MyD88-dependent BCG immunotherapy reduces tumor and regulates tumor microenvironment in bladder cancer murine model

“…BCG was grown in Middlebrook 7H9 broth that contained 0.05% Tween 80 and 0.2% glycerol and was supplemented with 10% albumin-dextrose-catalase. Cultures were harvested by centrifugation at the mid-exponential phase, suspended in saline containing 0.05% Tween 80, and stored at − 80 °C until use 90 .…”

“…At day seven in culture, the cells had completely differentiated into macrophages. Macrophages were seeded in 6-well plates (5 × 10 5 cells/well), 24-well plates (2 × 10 5 cells/well) or 96-well plates (1 × 10 5 cells/well) and used for in vitro studies as previously described 90 .…”