Is Intranasal Vaccination a Feasible Solution for Tuberculosis?
Bacille Calmette–Guerin (BCG) vaccine has been the only licensed tuberculosis (TB) vaccine administered to humans and, until today, more than 3 billion people have received BCG. However, despite the use of BCG, TB remains a global epidemic with a third of the world population being infected. Regardless of the protection induced by BCG in childhood TB, BCG vaccination fails to protect against pulmonary TB in adults, which represents more than 85% of the total TB burden. Therefore, the development of safe and efficacious TB vaccines that can confer potent protection in the lung mucosa has remained a major challenge to TB vaccinologists. Intranasal vaccination by different antigen formulations has shown promising results in the augmentation of immunity and the combat of the pathogens at the site of infection. This article will focus on the potential of intranasal vaccination and mucosal adjuvants for the development of new-generation TB vaccines.
In 1882, Robert Koch identified the tubercle bacillus, Mycobacterium tuberculosis, as the cause of tuberculosis (TB) in humans. This pathogen is still known as ‘the Koch's bacillus'. Even today, more than 100 years after Koch's description of how to stain and culture the tubercle bacillus, TB is still a major health problem worldwide and kills one person every 15 s. It is estimated that today, a third of the world population, that is, 2 billion people, has been infected with M. tuberculosis. Globally, 9.2 million new cases and 1.7 million deaths from TB occurred in 2006, of which 0.7 million cases and 0.2 million deaths were in HIV-positive people. The majority of TB cases occur in developing countries, making TB the number one killer among adults. If immediate measures are not taken to stop the spread of TB, the WHO estimates that within the next 20 years, 70 million people will die from infections caused by M. tuberculosis. One important reason for the increase in TB worldwide is the HIV epidemic. M. tuberculosis-infected, immunocompetent individuals have an estimated 10% lifetime risk of developing active disease. However, individuals who are immunocompromised by a HIV infection may easily experience reactivation of a previous TB infection. In these individuals, the risk of developing active disease increases from 10% per lifetime to 10% per year of life. With the increasing number of HIV-positive individuals and the emergence of multidrug-resistant (MDR) M. tuberculosis strains, the incidence of pulmonary TB is increasing. Bacille Calmette–Guerin (BCG) is the only vaccine currently available against TB and, unfortunately, it prevents only approximately 5% of all potentially vaccine-preventable deaths. It is clear that the development of new, better TB vaccines would be of great aid in implementing effective TB control programs.
Abstract and Introduction
Abstract
Bacille Calmette–Guerin (BCG) vaccine has been the only licensed tuberculosis (TB) vaccine administered to humans and, until today, more than 3 billion people have received BCG. However, despite the use of BCG, TB remains a global epidemic with a third of the world population being infected. Regardless of the protection induced by BCG in childhood TB, BCG vaccination fails to protect against pulmonary TB in adults, which represents more than 85% of the total TB burden. Therefore, the development of safe and efficacious TB vaccines that can confer potent protection in the lung mucosa has remained a major challenge to TB vaccinologists. Intranasal vaccination by different antigen formulations has shown promising results in the augmentation of immunity and the combat of the pathogens at the site of infection. This article will focus on the potential of intranasal vaccination and mucosal adjuvants for the development of new-generation TB vaccines.
Introduction
In 1882, Robert Koch identified the tubercle bacillus, Mycobacterium tuberculosis, as the cause of tuberculosis (TB) in humans. This pathogen is still known as ‘the Koch's bacillus'. Even today, more than 100 years after Koch's description of how to stain and culture the tubercle bacillus, TB is still a major health problem worldwide and kills one person every 15 s. It is estimated that today, a third of the world population, that is, 2 billion people, has been infected with M. tuberculosis. Globally, 9.2 million new cases and 1.7 million deaths from TB occurred in 2006, of which 0.7 million cases and 0.2 million deaths were in HIV-positive people. The majority of TB cases occur in developing countries, making TB the number one killer among adults. If immediate measures are not taken to stop the spread of TB, the WHO estimates that within the next 20 years, 70 million people will die from infections caused by M. tuberculosis. One important reason for the increase in TB worldwide is the HIV epidemic. M. tuberculosis-infected, immunocompetent individuals have an estimated 10% lifetime risk of developing active disease. However, individuals who are immunocompromised by a HIV infection may easily experience reactivation of a previous TB infection. In these individuals, the risk of developing active disease increases from 10% per lifetime to 10% per year of life. With the increasing number of HIV-positive individuals and the emergence of multidrug-resistant (MDR) M. tuberculosis strains, the incidence of pulmonary TB is increasing. Bacille Calmette–Guerin (BCG) is the only vaccine currently available against TB and, unfortunately, it prevents only approximately 5% of all potentially vaccine-preventable deaths. It is clear that the development of new, better TB vaccines would be of great aid in implementing effective TB control programs.
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