Spore-FP1 tuberculosis mucosal vaccine candidate is highly protective in guinea pigs but fails to improve on BCG-conferred protection in non-human primates.

Tuberculosis remains a major health threat globally and a more effective vaccine than the current Bacillus Calmette Guerin (BCG) is required, either to replace or boost it. The Spore-FP1 mucosal vaccine candidate is based on the fusion protein of Ag85B-Acr-HBHA/heparin-binding domain, adsorbed on the surface of inactivated Bacillus subtilis spores. The candidate conferred significant protection against Mycobacterium. tuberculosis challenge in naïve guinea pigs and markedly improved protection in the lungs and spleens of animals primed with BCG. We then immunized rhesus macaques with BCG intradermally, and subsequently boosted with one intradermal and one aerosol dose of Spore-FP1, prior to challenge with low dose aerosolized M. tuberculosis Erdman strain. Following vaccination, animals did not show any adverse reactions and displayed higher antigen specific cellular and antibody immune responses compared to BCG alone but this did not translate into significant improvement in disease pathology or bacterial burden in the organs.

Phase I Trial Evaluating the Safety and Immunogenicity of Candidate TB Vaccine MVA85A, Delivered by Aerosol to Healthy M.tb-Infected Adults.

The immunogenicity of the candidate tuberculosis (TB) vaccine MVA85A may be enhanced by aerosol delivery. Intradermal administration was shown to be safe in adults with latent TB infection (LTBI), but data are lacking for aerosol-delivered candidate TB vaccines in this population. We carried out a Phase I trial to evaluate the safety and immunogenicity of MVA85A delivered by aerosol in UK adults with LTBI (NCT02532036). Two volunteers were recruited, and the vaccine was well-tolerated with no safety concerns. Aerosolised vaccination with MVA85A induced mycobacterium- and vector-specific IFN-γ in blood and mycobacterium-specific Th1 cytokines in bronchoalveolar lavage. We identified several important barriers that could hamper recruitment into clinical trials in this patient population. The trial did not show any safety concerns in the aerosol delivery of a candidate viral-vectored TB vaccine to two UK adults with Mycobacterium tuberculosis (M.tb) infection. It also systemically and mucosally demonstrated inducible immune responses following aerosol vaccination. A further trial in a country with higher incidence of LTBI would confirm these findings.

Developing aerosol vaccines for Mycobacterium tuberculosis: Workshop proceedings: National Institute of Allergy and Infectious Diseases, Bethesda, Maryland, USA, April 9, 2014.

On April 9, 2014, Aeras and the National Institute of Allergy and Infectious Diseases convened a workshop entitled "Developing Aerosol Vaccines for Mycobacterium tuberculosis" in Bethesda, MD. The purpose of the meeting was to explore the potential for developing aerosol vaccines capable of preventing infection with M. tuberculosis (Mtb), preventing the development of active tuberculosis (TB) among those latently infected with Mtb, or as immunotherapy for persons with active TB. The workshop was organized around four key questions relevant to developing and assessing aerosol TB vaccines: (1) What is the current knowledge about lung immune responses and early pathogenesis resulting after Mtb infection and what are the implications for aerosol TB vaccine strategies? (2) What are the technical issues surrounding aerosol vaccine delivery? (3) What is the current experience in aerosol TB vaccine development? and (4) What are the regulatory implications of developing aerosol vaccines, including those for TB? Lessons learned from the WHO effort to develop an aerosol measles vaccine served as a case example for overall discussions at the meeting. Workshop participants agreed that aerosol delivery represents a potentially important strategy in advancing TB vaccine development efforts. As no major regulatory, manufacturing or clinical impediments were identified, members of the workshop emphasized the need for greater support to further explore the potential for this delivery methodology, either alone or as an adjunct to traditional parenteral methods of vaccine administration.

Development and validation of an attenuated Mycoplasma hyopneumoniae aerosol vaccine.

Mycoplasma hyopneumoniae (M. hyopneumoniae) causes a chronic respiratory disease with high morbidity and low mortality in swine, and has been presented as a major cause of growth retardation in the swine industry. Aerosol vaccination presents a needle free, high throughput, and efficient platform for vaccine delivery, and has been widely applied in poultry vaccination. However, aerosol vaccines have rarely been used in swine vaccination primarily because the long and curving respiratory track of swine presents a barrier for vaccine particle delivery. To develop an effective M. hyopneumoniae aerosol vaccine, three major barriers need to be overcome: to optimize particle size for aerosol delivery, to maintain the viability of mycoplasma cells in the vaccine, and to optimize the environmental conditions for vaccine delivery. In this study, an aerosol mycoplasma vaccine was successfully developed based on a conventional live attenuated M. hyopneumoniae vaccine. Specifically, the Pari LCD nebulizer was used to produce an aerosol vaccine particle size less than 5 µm; and a buffer with 5% glycerol was developed and optimized to prevent inactivation of M. hyopneumoniae caused by aerosolization and evaporation. Before nebulization, the room temperature and relative humidity were control to 20-25 °C and 70-75%, respectively, which helped maintain the viability of aerosol vaccine. Animal experiments demonstrated that this newly developed aerosol vaccine was effectively delivered to swine low respiratory track, being confirmed by nested-PCR, in situ hybridization and scanning electron microscope. Moreover, M. hyopneumoniae specific sIgA secretion was detected in the nasal swab samples at 14 days post-immunization. To our knowledge, this is the first report on a live M. hyopneumoniae aerosol vaccine.