Human gut microbial communities dictate efficacy of anti-PD-1 therapy in a humanized microbiome mouse model of glioma

Abstract

Background Although immunotherapy works well in glioblastoma (GBM) pre-clinical mouse models, the therapy has not demonstrated efficacy in humans. To address this anomaly, we developed a novel humanized microbiome (HuM) model to study the response to immunotherapy in a pre-clinical mouse model of GBM. Methods We used five healthy human donors for fecal transplantation of gnotobiotic mice. After the transplanted microbiomes stabilized, the mice were bred to generate five independent humanized mouse lines (HuM1-HuM5). Results Analysis of shotgun metagenomic sequencing data from fecal samples revealed a unique microbiome with significant differences in diversity and microbial composition among HuM1-HuM5 lines. All HuM mouse lines were susceptible to GBM transplantation, and exhibited similar median survival ranging from 19-26 days. Interestingly, we found that HuM lines responded differently to the immune checkpoint inhibitor anti-PD-1. Specifically, we demonstrate that HuM1, HuM4, and HuM5 mice are non-responders to anti-PD-1, while HuM2 and HuM3 mice are responsive to anti-PD-1 and displayed significantly increased survival compared to isotype controls. Bray-Curtis cluster analysis of the five HuM gut microbial communities revealed that responders HuM2 and HuM3 were closely related, and detailed taxonomic comparison analysis revealed that Bacteroides cellulosilyticus was commonly found in HuM2 and HuM3 with high abundances. Conclusions The results of our study establish the utility of humanized microbiome mice as avatars to delineate features of the host interaction with gut microbial communities needed for effective immunotherapy against GBM.

The Role of Gut Microbiota in Overcoming Resistance to Checkpoint Inhibitors in Cancer Patients: Mechanisms and Challenges

“…In a hybrid study design, Dees et al generated humanized microbiota murine model [ 69 ]. Fecal samples were derived from healthy human donors and then transplanted via oral gavage into GL261 brain-tumor-bearing gnotobiotic mice, sharing the same genetic strain [ 69 ]. HuM1–HuM5 were the humanized-microbiota bearing mice, and MuM were the controls with murine microbiota only.…”

“…HuM1–HuM5 were the humanized-microbiota bearing mice, and MuM were the controls with murine microbiota only. HuM2 and HuM3 mice exhibited a strong positive response to PD-1 antibody therapy, manifested by a slower rate of tumor growth and prolonged survival [ 69 ]. However, HuM1, HuM4 and HuM5 displayed resistance to immunotherapy.…”

“…On further analysis of cytokine expression and T-cell population percentages, responder mice HuM2 demonstrated a significant enrichment in INF-γ production, increase in cytotoxic CD8 + and CD4 + T cells and the CD8 + /Treg ratio as compared to resistant HuM1 mice [ 69 ]. Taxonomic distribution analysis of microbial communities showed close clustering of the HuM2 and HuM3 microbes, indicating similarities in composition and the potential underlying mechanism to enhance therapeutic effectiveness [ 69 ]. Bacteroides cellulosilyticus were found in abundance in these two groups, and B. caccae specifically in HuM2.…”

“…Bacteroides cellulosilyticus were found in abundance in these two groups, and B. caccae specifically in HuM2. Treatment with antibiotics prevented PD-1 antibody therapy efficacy in HuM2, hence the vital role of HuM2 microbes in modulating immune response [ 69 ].…”

Anti-PD-1 checkpoint blockade monotherapy in the orthotopic GL261 glioma model: the devil is in the detail

“… 69 While these vendor-specific effects have been underexplored in the context of the glioma models, the gut microbiome has been implicated both in responsiveness to anti-PD-1 CBI in humans 70–72 and in controlling glioma progression 73 and anti-PD-1 responsiveness in the GL261 model. 74 It could certainly be possible for C57BL/6 mice from different vendors to respond differently both to glioma inoculation and to treatment with anti-PD-1 on the grounds of either slight genetic alterations or shifts in gut microbiome, and these potential sources of variability should be explored further.…”