c Needle-free, mucosal immunization is a highly desirable strategy for vaccination against many pathogens, especially those entering through the respiratory mucosa, such as Mycobacterium tuberculosis. Unfortunately, mucosal vaccination against tuberculosis (TB) is impeded by a lack of suitable adjuvants and/or delivery platforms that could induce a protective immune response in humans. Here, we report on a novel biotechnological approach for mucosal vaccination against TB that overcomes some of the current limitations. This is achieved by coating protective TB antigens onto the surface of inert bacterial spores, which are then delivered to the respiratory tract. Our data showed that mice immunized nasally with coated spores developed humoral and cellular immune responses and multifunctional T cells and, most importantly, presented significantly reduced bacterial loads in their lungs and spleens following pathogenic challenge. We conclude that this new vaccine delivery platform merits further development as a mucosal vaccine for TB and possibly also other respiratory pathogens.
Athird of the world's population is estimated to be infected with Mycobacterium tuberculosis, the causative pathogen of tuberculosis (TB). Although the incidence of TB has been slowly decreasing from year to year, this disease still accounts for over a million deaths per annum, mostly in the developing world. TB, however, is also beginning to have an impact on the more developed nations, for example, because of the increased levels of people movement and international travel, which only serve to disseminate TB. Controlling TB relies on a number of strategies, including vaccination, drug therapy, and improved living standards. However, only improved living standards have been shown to have any real impact, and both the current TB drugs and vaccination strategies carry a number of inherent flaws. With drug therapy, multiresistant strains of M. tuberculosis and, more recently, extensively drug-resistant (XDR) M. tuberculosis variants have emerged, showing that drug development may, at most, produce only a short-term impact. The current vaccine against TB, M. bovis BCG, is generally considered unsatisfactory because of its variable efficacy (in different parts of the world) and the shortlived protection that it confers, especially against the reactivated pulmonary form of the disease. For these reasons, BCG is no longer routinely used in some countries.Bearing in mind these concerns, a better vaccine is now a priority. It should be noted that the results of the first-ever efficacy trial (phase 2b) of a new TB vaccine (MVA85A) that could boost the efficacy of BCG was concluded in early 2013 but with disappointing results (1). Although other trials are planned or are in progress for at least nine other TB vaccines, it is clear that the tasks ahead will be challenging. There are some important issues regarding the design of TB vaccines that might now be reconsidered, for example, the general assumption that cellular responses are of paramount imp...