Understanding vaccine induced protective immunity to Mycobacterium tuberculosis

Thesis

The current worldwide epidemic of Mycobacterium tuberculosis infection is a huge global health problem. Widespread BCG vaccination remains a useful tool in combating this epidemic; however, its variable efficacy requires urgent development of novel vaccines against Mycobacterium tuberculosis. Such a candidate vaccine is a serotype 5 adenovirus expressing antigen 85A from M. tuberculosis (Ad85A). In animal models Ad85A confers significant protection when administered intra-nasally. The work in this thesis demonstrates that intra-nasal immunisation with Ad85A results in inhibition of M. tuberculosis growth in the lung early after infection, in contrast to the late inhibition induced by parenterally administered vaccines. Early inhibition correlates with the presence in the lung of a highly activated population of antigen-specific CD8 T cells, maintained for at least 6 months post-immunisation by persistent antigen. For intra-nasal Ad85A to be effective, the vaccine must be delivered into the lower respiratory tract, as immunisation targeting only the nasal-associated lymphoid tissue (NALT) does not result in protection. Following a change of animal facility, the lung immune response to intra-dermal immunisation with Ad85A increased and this route of immunisation now induced protection, though growth of M. tuberculosis was inhibited only late after infection. However, this response and protection can be altered by exposure to environmental mycobacteria. Further experiments showed that simultaneous respiratory and parenteral immunisations (SIM) act additively, where local lung immunity inhibits the growth of M. tuberculosis early after infection and systemic immunity protects later. SIM regimes generate greatly improved protection over either immunisation alone and do not depend on priming and boosting.

Authors: Ronan, E

• Publication date: 2011
• DOI: 10.5287/ora-vj5rvdx8g
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: Oxford University, UK
• Language: English
• Keywords: T cell; Vaccine; Lung; Tuberculosis
• Subjects: Immunology; Infectious diseases; Vaccinology; Biology (medical sciences)