Immunoprophylaxis of Tuberculosis: An Update of Emerging Trends

Abstract

Developing effective prophylactics to combat tuberculosis is currently in an exploratory stage. The HIV pandemic and emergence of multi- and extensively drug-resistant strains of Mycobacterium tuberculosis indicate that the current preventive measures against this ever-evolving pathogen are inadequate. The currently available vaccine BCG in its present form affords variable protection which usually wanes with aging. Various reasons have been cited to explain the discrepancies in the efficacy of BCG, including generic differences in the different BCG vaccine strains used in immunization program throughout the world. The low efficacy of BCG vaccine has promoted the search for novel vaccines for tuberculosis. The search strategies aim at completely replacing the existing vaccine and/or augmenting/improving the current BCG vaccine. Among new vaccine candidates are live attenuated M. tuberculosis vaccines, recombinant BCG, DNA vaccines, subunit vaccine, and fusion protein-based vaccines. More than 200 new vaccine candidates have been developed as a result of research work over the past few years. To date, at least eight vaccine candidates are undergoing clinical evaluation, with a few of them successfully qualifying in the first phase of clinical testing. These recent advances present an optimistic insight whereby a new tuberculosis vaccine might be expected to be available for public use in the next few years.

Protection of mice from Mycobacterium tuberculosis by ID87/GLA-SE, a novel tuberculosis subunit vaccine candidate

“…The live, attenuated vaccine, M. bovis Bacillus Calmette-Guérin (BCG), has been routinely administered to infants and children since 1921, preventing tuberculosis (TB) dissemination and TB meningitis in children, but not preventing infection or active pulmonary TB (reviewed in [2, 3]). Results from BCG efficacy trials indicate disparate levels of protection, ranging from a complete lack of protection to protection for more than 50 years (reviewed in [4]). This variability may be attributed to the use of different BCG vaccine strains or immunization strategies, both of which vary in distinct geographic regions [4].…”

“…Results from BCG efficacy trials indicate disparate levels of protection, ranging from a complete lack of protection to protection for more than 50 years (reviewed in [4]). This variability may be attributed to the use of different BCG vaccine strains or immunization strategies, both of which vary in distinct geographic regions [4]. Regardless, the prevalent belief is that protection afforded by childhood BCG vaccination wanes over the course of a couple of decades such that young adults are no longer protected.…”