We have previously observed a potential role for the gut microbiota (GM) in peripheral neuropathy (PN) caused by the anti-myeloma drug, bortezomib, with faecal microbiota transplantation (FMT) altering symptom profiles in germ-free mice. Here, we aimed to extend these findings to determine: i) if people with bortezomib-induced PN have distinct a GM composition compared with those without symptoms, and ii) if PN symptoms could be transferred from humans to mice via FMT.
Myeloma patients treated with bortezomib were recruited (August 2023-May 2024) in South Australia (n=29; 66.9±2.07 years; 55% female). PN severity was determined using the validated tool, CIPN8, and faecal samples collected for shotgun metagenomic analysis. Participants were classified as low-PN or moderate/high-PN (CIPN8 score≤/>cohort median, respectively). Faecal samples from two moderate/high-PN participants (hD1=low GM diversity; hD2=high PN severity) were transferred to germ-free mice (N=12/donor) via oral gavage. Mice were treated with vehicle or bortezomib (0.5mg/kg) intravenously for two weeks. PN-associated symptoms were assessed using behavioural phenotyping and von Frey mechanical sensitivity testing in paws.
People with moderate/high-PN (N=14) had reduced microbial diversity (Shannon index; 3.55±0.137) compared with the low-PN group (2.94±0.132, P=0.0038). The GM of moderate/high-PN participants were enriched for taxa associated with rheumatoid arthritis (FDR=0.01), and depleted for taxa producing isovaleric acid (FDR=0.08). Transfer of a human PN-GM to germ-free mice did not induce overt symptoms of PN; however, the combination of a GM transfer from hD2 and bortezomib treatment increased time spent still compared with treatment-naïve germ-free mice (P=0.0211).
These data reinforce the emerging role of the GM in PN, however underscore the complexity of GM-drug-neural interactions and PN aetiology. Although subtle, the induction of behavioural deficits consistent with bortezomib treatment following human-to-mouse GM transfer warrants further investigation with increased numbers of donors and recipient mice to determine whether these effects are statistically and clinically meaningful.