Abstract
Currently available vaccines fail to provide consistent protection against tuberculosis (TB). New, improved vaccines are urgently needed for controlling the disease. The mycobacterial antigen fusions H4 (Ag85B-TB10.4) and H28 (Ag85B-TB10.4-Rv2660c) have been shown to be very immunogenic and have been considered as potential candidates for TB vaccine development. However, soluble protein vaccines are often poorly immunogenic, but augmented immune responses can be induced when selected antigens are delivered in particulate form. This study investigated whether the mycobacterial antigen fusions H4 and H28 can induce protective immunity when assembled into particulate vaccines (polyester nanoparticle-H4, polyester nanoparticle-H28, H4 nanoparticles and H28 nanoparticles). The particulate mycobacterial vaccines were assembled inside an engineered endotoxin-free production strain of Escherichia coli at high yield. Vaccine nanoparticles were purified and induced long-lasting antigen-specific T cell responses and protective immunity in mice challenged by aerosol with virulent Mycobacterium tuberculosis. A significant reduction of M. tuberculosis CFU, up to 0.7-log10 protection, occurred in the lungs of mice immunized with particulate vaccines in comparison to placebo-vaccinated mice (p < 0.0001). Polyester nanoparticles displaying the mycobacterial antigen fusion H4 induced a similar level of protective immunity in the lung when compared to M. bovis bacillus Calmette-Guérin (BCG), the currently approved TB vaccine. The safe and immunogenic polyester nanoparticle-H4 vaccine is a promising subunit vaccine candidate, as it can be cost-effectively manufactured and efficiently induces protection against TB.
Highlights
IntroductionTuberculosis (TB) is a major health burden, as more than 2 billion people are infected with Mycobacterium tuberculosis (M. tuberculosis) worldwide
We previously showed that these two mycobacterial antigen fusions, H4 and H28, can be engineered to self-assemble into various particulate mycobacterial vaccines in E. coli cells
We have investigated whether the mycobacterial fusions H4 and/or H28 delivered as defined polyester or protein nanoparticles could induce protective immunity in a mouse model of aerosol M. tuberculosis infection
Summary
Tuberculosis (TB) is a major health burden, as more than 2 billion people are infected with Mycobacterium tuberculosis (M. tuberculosis) worldwide. The World Health Organization (WHO) estimates that approximately 10 million people develop active TB and 1.4 million people die from TB every year, making TB the leading infectious disease killer [1]. The immunocompromised population has a much higher risk for developing active TB, and this includes people with HIV infection, malnutrition or diabetes [2,3,4]. The spread of drug-resistant forms of TB is a growing threat to global public health [5,6]. Developing interventions to prevent TB is a crucial global health priority [7,8].
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