Nastassja Kriel Poster 2025

Dr Nastassja Kriel

Stellenbosch University, South Africa

Secretome characterization of viable but non-replicating enriched M. tuberculosis culture for TB vaccine candidate discovery

Poster Abstract

Mycobacterium tuberculosis (Mtb) persisters, a sub-population of viable but non-replicating (VBNR) bacteria, may prevent successful treatment due to their slow or non-replicating nature and antibiotic recalcitrance. Persisters increase the risk of treatment failure and disease recurrence following treatment. The persister phenotype is reversible and can be induced by environmental stress such as starvation, changes in pH and antibiotic exposure, as experienced by Mtb during infection and treatment. Mtb secretes proteins that modulate the host immune response and persister Mtb may secrete proteins which enable long-term survival following infection.

We recently showed that TB clinical isolates obtained from patients with undesirable treatment outcomes had an increased propensity to form VBNR subpopulations. In this study, one of these drug sensitive clinical isolates transformed with a replication reporter plasmid was subjected to a low pH stress model. Low pH stress induced the formation of a VBNR subpopulation (19.7% average from three biological replicates). Culture supernatants from both actively replicating and low pH stress cultures were filter sterilized, pH neutralized and concentrated prior to protein capture on magnetic beads. Proteomics was used to characterize the secretomes of actively replicating and VBNR enriched culture filtrates. We identified a total of 315 proteins of which 188 were unique to the actively replicating Mtb and 44 proteins were only identified in the secretomes of VBNR enriched Mtb cultures.

Characterization of the Mtb secretome in response to low pH stress, as experienced during infection, may identify effector proteins of immune modulation. Proteins found exclusively in the secretomes of VBNR enriched cultures are potential vaccine development candidates not only for the prevention of TB, but also to prevent reactivation of persister cells for disease recurrence.

Biography

Dr Nastassja Kriel is a tuberculosis researcher at Stellenbosch University in South Africa. Her research aims to improve our understanding of Mycobacterium tuberculosis persisters, a subpopulation of viable but non-replicating and antibiotic tolerant mycobacteria. She makes use of molecular mycobacteriology and mass spectrometry-based proteomics to study how subpopulations of TB respond to changes within its environment. Prevention of Mycobacterium tuberculosis persister formation has the potential to shorten anti-TB therapy and decelerate the development of drug resistance.