title: Secretory phosphatases deficient mutant of Mycobacterium tuberculosis imparts protection at the primary site of infection in guinea pigs.
abstract: BACKGROUND
  The failure of Mycobacterium bovis Bacille Calmette-Guérin to impart satisfactory protection against adult pulmonary tuberculosis has necessitated the development of more effective TB vaccines. The assumption that the vaccine strain should be antigenically as similar as possible to the disease causing pathogen has led to the evaluation of M.tuberculosis mutants as candidate tuberculosis vaccines.
  
  
  RESULTS
  In this study, we have generated a mutant of M.tuberculosis (Mtb∆mms) by disrupting 3 virulence genes encoding a mycobacterial secretory acid phosphatase (sapM) and two phosphotyrosine protein phosphatases (mptpA and mptpB) and have evaluated its protective efficacy in guinea pigs. We observed that Mtb∆mms was highly attenuated in THP-1 macrophages. Moreover, no bacilli were recovered from the lungs and spleens of guinea pigs after 10 weeks of Mtb∆mms inoculation, although, initially, the mutant exhibited some growth in the spleens. Subsequently, when Mtb∆mms was evaluated for its protective efficacy, we observed that similar to BCG vaccination, Mtb∆mms exhibited a significantly reduced CFU in the lungs of guinea pigs when compared with the unvaccinated animals at 4 weeks after challenge. In addition, our observations at 12 weeks post challenge demonstrated that Mtb∆mms exhibited a more sustainable and superior protection in lungs as compared to BCG. However, the mutant failed to control the hematogenous spread as the splenic bacillary load between Mtb∆mms vaccinated and sham immunized animals was not significantly different. The gross pathological observations and histopathological observations corroborated the bacterial findings. Inspite of disruption of phosphatase genes in MtbΔmms, the lipid profiles of M.tuberculosis and MtbΔmms were identical indicating thereby that the phenotype of the mutant was ascribed to the loss of phosphatase genes and the influence was not related to any alteration in the lipid composition.
  
  
  CONCLUSIONS
  This study highlights the importance of M.tuberculosis mutants in imparting protection against pulmonary TB.
authors.affiliation: Department of Biochemistry, University of Delhi South Campus, New Delhi, India.
authors.forename: Priyanka
authors.initials: P
authors.lastname: Chauhan
authors.forename: P Vineel
authors.initials: PV
authors.lastname: Reddy
authors.forename: Ramandeep
authors.initials: R
authors.lastname: Singh
authors.forename: Neetika
authors.initials: N
authors.lastname: Jaisinghani
authors.forename: Sheetal
authors.initials: S
authors.lastname: Gandotra
authors.forename: Anil K
authors.initials: AK
authors.lastname: Tyagi
mesh_terms: D000818:Animals; D015139:Blotting, Southern; D015169:Colony Count, Microbial; D005260:Female; D006168:Guinea Pigs; D008168:Lung / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D008264:Macrophages / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D009154:Mutation / Q000235:genetics*; D009169:Mycobacterium tuberculosis / Q000201:enzymology* / Q000235:genetics; D010744:Phosphoric Monoester Hydrolases / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism; D013154:Spleen / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D032581:Tuberculosis Vaccines / Q000627:therapeutic use*; D014397:Tuberculosis, Pulmonary / Q000235:genetics / Q000382:microbiology / Q000517:prevention & control*; D014774:Virulence / Q000235:genetics
chemical_list: D032581:Tuberculosis Vaccines; D010744:Phosphoric Monoester Hydrolases