Gain of function in Mycobacterium bovis BCG Moreau due to loss of a transcriptional repressor

Abstract

The Bacille Calmette-Guérin (BCG) vaccine comprises a family of genetically different strains derived by the loss of genomic regions (RDs) and other mutations. In BCG Moreau, loss of RD16 inactivates rv3405c * , encoding a transcriptional repressor that negatively regulates the expression of Rv3406, an alkyl sulfatase. To evaluate the impact of this loss on the BCG and host cell viability and the cytokine profile, THP-1 cells were infected with BCG Moreau (harbouring the empty vector) and a complemented strain carrying a functional copy of rv3405c. Viability of the host cells and bacteria as well as the pattern of cytokine secretion were evaluated. Our results show that the viability of BCG Moreau is higher than that of the complemented strain in an axenic medium, suggesting a possible functional gain associated with the constitutive expression of Rv3406. Viability of the host cells did not vary significantly between recombinant strains, but differences in the profiles of the cytokine secretion (IL-1β and IL-6) were observed. Our results suggest an example of a functional gain due to gene loss contributing to the elucidation of the impact of RD16 on the physiology of BCG Moreau.

Mycobacterium tuberculosis and M. bovis BCG Moreau Fumarate Reductase Operons Produce Different Polypeptides That May Be Related to Non-canonical Functions

“…The strain used in Brazil from 1928 until 2017 is M. bovis BCG Moreau, phylogenetically close to BCG Russia and Japan, all of them considered to be more immunogenic and closer to the original BCG. Our group has been working on its molecular characterization, also using it as a model to better understand mycobacterial biology ( Berrêdo-Pinho et al, 2011 ; Gomes et al, 2011 ; Galvão et al, 2014 ; Monteiro-Maia et al, 2018 ; Pagani et al, 2019 ). Analysis of the FRD operon DNA sequence in BCG Moreau shows a mutation in a poly-G homopolymeric region at the end of frdB , when compared to M.tb .…”

M. bovis BCG Moreau N-Terminal Loss Leads to a Less Stable Dodecin With Lower Flavin Binding Capacity

“…But even with the long, continuous usage of this strain for vaccination of Brazilian children, little is known about BCG Moreau physiology, when compared to BCG Pasteur, one of the most studied BCG strains, M. bovis or M.tb . In the last decade, our group worked on its characterization, on the genomic ( Gomes et al., 2011 ), proteomic ( Berrêdo-Pinho et al., 2011 ; Pagani et al., 2019 ) and functional context ( Galvão et al., 2014 ; Monteiro-Maia et al., 2018 ; Schwarz et al., 2020 ; Schwarz et al., 2021 ). Comparison of the BCG Moreau and M.tb genomes confirms a single nucleotide polymorphism (SNP) within the start codon of the dodecin coding gene, already annotated, but not functionally described, for BCG Pasteur (BCG_1562c), leading to a predicted N-terminal shorter homolog in BCG.…”

Table_1.DOCX

“…The strain used in Brazil from 1928 until 2017 is M. bovis BCG Moreau, phylogenetically close to BCG Russia and Japan, all of them considered to be more immunogenic and closer to the original BCG. Our group has been working on its molecular characterization, also using it as a model to better understand mycobacterial biology (Berrêdo-Pinho et al, 2011;Gomes et al, 2011;Galvão et al, 2014;Monteiro-Maia et al, 2018;Pagani et al, 2019). Analysis of the FRD operon DNA sequence in BCG Moreau shows a mutation in a poly-G homopolymeric region at the end of frdB, when compared to M.tb.…”