title: A booster vaccine expressing a latency-associated antigen augments BCG induced immunity and confers enhanced protection against tuberculosis.
abstract: BACKGROUND
  In spite of a consistent protection against tuberculosis (TB) in children, Mycobacterium bovis Bacille Calmette-Guerin (BCG) fails to provide adequate protection against the disease in adults as well as against reactivation of latent infections or exogenous reinfections. It has been speculated that failure to generate adequate memory T cell response, elicitation of inadequate immune response against latency-associated antigens and inability to impart long-term immunity against M. tuberculosis infections are some of the key factors responsible for the limited efficiency of BCG in controlling TB.
  
  
  RESULTS
  In this study, we evaluated the ability of a DNA vaccine expressing α-crystallin--a key latency antigen of M. tuberculosis to boost the BCG induced immunity. 'BCG prime-DNA boost' regimen (B/D) confers robust protection in guinea pigs along with a reduced pathology in comparison to BCG vaccination (1.37 log(10) and 1.96 log(10) fewer bacilli in lungs and spleen, respectively; p<0.01). In addition, B/D regimen also confers enhanced protection in mice. Further, we show that B/D immunization in mice results in a heightened frequency of PPD and antigen specific multi-functional CD4 T cells (3(+)) simultaneously producing interferon (IFN)γ, tumor necrosis factor (TNF)α and interleukin (IL)2.
  
  
  CONCLUSIONS
  These results clearly indicate the superiority of α-crystallin based B/D regimen over BCG. Our study, also demonstrates that protection against TB is predictable by an increased frequency of 3(+) Th1 cells with superior effector functions. We anticipate that this study would significantly contribute towards the development of superior booster vaccines for BCG vaccinated individuals. In addition, this regimen can also be expected to reduce the risk of developing active TB due to reactivation of latent infection.
authors.affiliation: Department of Biochemistry, University of Delhi South Campus, New Delhi, India.
authors.forename: Bappaditya
authors.initials: B
authors.lastname: Dey
authors.forename: Ruchi
authors.initials: R
authors.lastname: Jain
authors.forename: Umesh D
authors.initials: UD
authors.lastname: Gupta
authors.forename: V M
authors.initials: VM
authors.lastname: Katoch
authors.forename: V D
authors.initials: VD
authors.lastname: Ramanathan
authors.forename: Anil K
authors.initials: AK
authors.lastname: Tyagi
mesh_terms: D000328:Adult; D000818:Animals; D001500:BCG Vaccine / Q000008:administration & dosage / Q000276:immunology*; D001426:Bacterial Proteins / Q000235:genetics / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000187:drug effects / Q000276:immunology / Q000378:metabolism; D004353:Drug Evaluation, Preclinical; D004357:Drug Synergism; D005260:Female; D005434:Flow Cytometry; D006099:Granuloma / Q000276:immunology / Q000473:pathology / Q000517:prevention & control; D006168:Guinea Pigs; D006801:Humans; D007117:Immunization, Secondary / Q000379:methods; D007371:Interferon-gamma / Q000276:immunology / Q000378:metabolism; D007668:Kidney / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D008168:Lung / Q000187:drug effects / Q000276:immunology / Q000473:pathology; D008171:Lung Diseases / Q000276:immunology / Q000473:pathology / Q000517:prevention & control; D051379:Mice; D008807:Mice, Inbred BALB C; D009163:Mycobacterium bovis / Q000276:immunology; D009169:Mycobacterium tuberculosis / Q000235:genetics / Q000276:immunology*; D014376:Tuberculosis / Q000276:immunology* / Q000517:prevention & control; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000378:metabolism; D019444:Vaccines, DNA / Q000008:administration & dosage / Q000276:immunology*; D038201:alpha-Crystallins / Q000235:genetics / Q000276:immunology*
chemical_list: D001500:BCG Vaccine; D001426:Bacterial Proteins; D014409:Tumor Necrosis Factor-alpha; D019444:Vaccines, DNA; D038201:alpha-Crystallins; D007371:Interferon-gamma