Regulation of Neurotoxin Expression by Culture Conditions.

Background: Ensuring consistency of tetanus neurotoxin (TeNT) production by could help to ensure consistent product quality in tetanus vaccine manufacturing, ultimately contributing to reduced animal testing. The aim of this study was to identify RNA signatures related to consistent TeNT production using standard and non-standard culture conditions.

Methods: We applied RNA sequencing (RNA-Seq) to study gene expression in small-scale batches under several culture conditions.

Results: We identified 1381 time-dependent differentially expressed genes (DEGs) reflecting, among others, changes in growth rate and metabolism. Comparing non-standard versus standard culture conditions identified 82 condition-dependent DEGs, most of which were specific for one condition. The tetanus neurotoxin gene () was highly expressed but showed expression changes over time and between culture conditions. The gene showed significant down-regulation at higher pH levels (pH 7.8), which was confirmed by the quantification data obtained with the recently validated targeted LC-MS/MS approach.

Conclusions: Non-standard culture conditions lead to different gene expression responses. The gene appears to be the best transcriptional biomarker for monitoring TeNT production as part of batch-to-batch consistency testing during tetanus vaccine manufacturing.