The cyclic di-GMP phosphodiesterase geneRv1357c/BCG1419caffects BCG Pellicle production andIn Vivomaintenance

Abstract

Bacteria living in a surface-attached community that contains a heterogeneous population, coated with an extracellular matrix, and showing drug tolerance (biofilms) are often linked to chronic infections. In mycobacteria, the pellicle mode of growth has been equated to an in vitro biofilm and meets several of the criteria mentioned above, while tuberculosis infection presents a chronic (latent) phase of infection. As mycobacteria lack most genes required to control biofilm production by other microorganisms, we deleted or expressed from the hsp60 strong promoter the only known c-di-GMP phosphodiesterase (PDE) gene in Mycobacterium bovis BCG. We found changes in pellicle production, cellular protein profiles, lipid production, resistance to nitrosative stress and maintenance in lungs and spleens of immunocompetent BALB/mice. Our results show that pellicle production and capacity to remain within the host are linked in BCG. V C 2015 IUBMB Life, 67(2): [129][130][131][132][133][134][135][136][137][138] 2015

The BCGΔBCG1419c Vaccine Candidate Reduces Lung Pathology, IL-6, TNF-α, and IL-10 During Chronic TB Infection

“…In order to explore the hypothesis that mycobacterial biofilms resemble aspects of chronic TB infection ( Flores-Valdez, 2016 ), we deleted the cyclic di-GMP phosphodiesterase-encoding gene BCG1419c , to create the BCGΔBCG1419c Pasteur-derivative strain ( Flores-Valdez et al, 2015 ). We previously showed that in immunocompromised nu/nu mice, BCGΔBCG1419c was as safe as parental BCG, and that in a mouse model of progressive infection with M. tuberculosis H37Rv, compared to BCG, vaccination with BCGΔBCG1419c increased the levels of CD4 + and CD8 + T lymphocytes, and reduced 1-log 10 bacterial burden in lungs after 24 weeks post-infection, with reduced pneumonia, indicating its potential as a preventive vaccine against chronic TB ( Pedroza-Roldán et al, 2016 ).…”

Vaccines Directed Against Microorganisms or Their Products Present During Biofilm Lifestyle: Can We Make a Translation as a Broad Biological Model to Tuberculosis?

“…Most manufacturers grow BCG for vaccine administration to humans, as a surface pellicle in liquid Sauton medium (Eickhoff, 1977 ). We have shown that Sauton medium favors formation of pellicle compared to Middlebrook 7H9 (Flores-Valdez et al, 2015 ), and others already demonstrated that pellicle mode of growth in Sauton medium render BCG more able to persist within macrophages, induce stronger inflammatory response but ultimately resulted in less control of bacterial replication in lungs of aerosol infected C57BL/six mice, after 3 months of infection with low dose M. tuberculosis H37Rv (Venkataswamy et al, 2012 ). Based on these results, it seems rather logical to think that biofilm mode of growth has not proven to be a useful source of antigens to protect against pulmonary and latent TB.…”

“…In term of the capacity to remain within the host, we have recently shown that pellicle production and persistence in immunocompetent mice are linked in BCG (Flores-Valdez et al, 2015 ), and there is evidence that a BCG strain more capable of producing pellicles protects better than parental BCG against TB in mice, particularly at 6 months post-infection or upon reactivation from persistent infection (Pedroza-Roldán et al, in preparation). The use of this vaccine candidate in animal models such as Non-Human Primates (NHP), which more closely reproduce latent infection, should allow us to determine whether biofilms share some aspects of this clinically relevant infection stage.…”

“…Bacteria living within a structure comprising metabolically and phenotypically diverse cells, covered by an extracellular matrix are often termed biofilms and compared to free-living (planktonic) cells have been shown to be more tolerant to drug treatment, induce different immune response and persist longer within infected tissues in vivo (Ojha et al, 2008 ). Considering that tuberculosis is characterized for chronicity of infection, as well as the known need of prolonged multiple antibiotic treatment to manage TB, even in drug-susceptible cases, it has been proposed that mycobacterial biofilms, where bacteria grow to produce a thick aggregate of mycolic acids at the air-liquid interface and exhibit increased phenotypic resistance to antibiotics (Ojha et al, 2008 ), might mimic aspects found during in vivo infection (Flores-Valdez et al, 2015 ), and that perhaps drug-persisters found in Guinea pigs might constitute some sort of biofilm (Orme, 2014 ).…”

Diguanylate cyclase activity of the Mycobacterium leprae T cell antigen ML1419c

“…Disruption of Rv1354c PDE activity decreases the pathogenicity and dormancy in M. tuberculosis (Hong et al, 2013). In addition, studies of cyclic di-GMP PDE activity of Rv1357c in the closely related Mycobacterium bovis BCG Pasteur 1173P2 demonstrated that cyclic di-GMP was associated with the regulation of lipid production and pellicle growth and promoted resistance to nitrosative stress (Flores-Valdez et al, 2015). Protein interaction studies have also suggested that cyclic di-GMP production in M. tuberculosis is involved in regulation of rhamnose biosynthesis, a key sugar in the formation of the mycobacterial cell wall (Deng et al, 2014).…”