An attenuated quadruple gene mutant of Mycobacterium tuberculosis imparts protection against tuberculosis in guinea pigs.

Ritika Kar Bahal,Priyanka Chauhan,Anil K Tyagi,Shubhita Mathur

doi:10.1242/bio.029546

Abstract

ABSTRACTPreviously we had developed a triple gene mutant of Mycobacterium tuberculosis (MtbΔmms) harboring disruption in three genes, namely mptpA, mptpB and sapM. Though vaccination with MtbΔmms strain induced protection in the lungs of guinea pigs, the mutant strain failed to control the hematogenous spread of the challenge strain to the spleen. Additionally, inoculation with MtbΔmms resulted in some pathological damage to the spleens in the early phase of infection. In order to generate a strain that overcomes the pathology caused by MtbΔmms in spleen of guinea pigs and controls dissemination of the challenge strain, MtbΔmms was genetically modified by disrupting bioA gene to generate MtbΔmmsb strain. Further, in vivo attenuation of MtbΔmmsb was evaluated and its protective efficacy was assessed against virulent M. tuberculosis challenge in guinea pigs. MtbΔmmsb mutant strain was highly attenuated for growth and virulence in guinea pigs. Vaccination with MtbΔmmsb mutant generated significant protection in comparison to sham-immunized animals at 4 and 12 weeks post-infection in lungs and spleen of infected animals. However, the protection imparted by MtbΔmmsb was significantly less in comparison to BCG immunized animals. This study indicates the importance of attenuated multiple gene deletion mutants of M. tuberculosis for generating protection against tuberculosis.

Highlights

Mycobacterium tuberculosis, the causative agent of human tuberculosis (TB) continues to be a major cause of mortality
In order to generate a strain that overcomes the pathology caused by MtbΔmms in spleen of guinea pigs and controls dissemination of the challenge strain, MtbΔmms was genetically modified by disrupting bioA gene to generate MtbΔmmsb strain
This study indicates the importance of attenuated multiple gene deletion mutants of M. tuberculosis for generating protection against tuberculosis

Summary

Introduction

Mycobacterium tuberculosis, the causative agent of human tuberculosis (TB) continues to be a major cause of mortality. Et al, 2007, Smith et al, 2001) Strains such as lysA panCD and leuD panCD demonstrated negligible multiplication in mouse organs yet generated protection equivalent to BCG (Sambandamurthy et al, 2005, Sampson et al, 2004). We have earlier reported that disruption of bioA renders M. tuberculosis severely attenuated for growth and virulence in guinea pig along with negligible granulomatous pathology (Kar et al, 2017). Immunization with MtbΔbioA imparted significant protection in lungs and spleen when compared to sham-immunized animals demonstrating an efficient control over the dissemination of infecting strain to the spleen (Kar et al, 2017). We evaluated in vivo attenuation and assessed the protective efficacy of MtbΔmmsb against virulent M. tuberculosis challenge in guinea pigs

Materials and methods

Ethics statement

Results

Discussion

Conclusion