Simultaneous parenteral and pulmonary immunisation against tuberculosis

Two million individuals die each year from tuberculosis infection, which is an increasing problem because HIV/AIDS makes individuals highly susceptible and because antibiotic resistant strains of Mycobacterium tuberculosis are appearing. The present tuberculosis vaccine, BCG, is only partially effective, so development of a better vaccine is an urgent health care priority. Up to now, most new tuberculosis vaccines have been designed to be given after BCG, in order to boost the weak immunity provided by BCG. This is called prime boost immunisation. However, it is becoming clear that prime boost immunisation may not be sufficiently effective to control tuberculosis.
In this project we will establish an alternative novel immunisation strategy called Simultaneous Immunisation (SIM). We have already shown that giving one tuberculosis vaccine by injection and simultaneously spraying another into the lungs is highly effective in mice. The lung vaccine establishes local immunity, which combats tuberculosis infection immediately after infection, and the injected vaccine has a slower effect, but the two work very effectively together. We now want to test several different SIM regimes in mice to find the most effective one and test its safety. We will also study how different white cells combine to protect the lungs against tuberculosis, in order to make even more effective vaccines in the future. At the same time we will study humans infected with tuberculosis to develop better tests to assess immunity to tuberculosis. This will help in testing new immunisation procedures, including SIM, in man. A better tuberculosis vaccine will have major health benefits for humans and can also be used to control bovine tuberculosis, which is currently widespread in the UK and causes considerable economic losses.

Tuberculosis vaccinology is dominated by the prime boost paradigm. In this project we will establish the novel concept of simultaneous immunisation (SIM) against Mycobacterium tuberculosis (Mtb). We will determine the roles of different lung and peripheral lymphocyte populations in protective immunity induced by SIM in mice, and develop assays for protective pulmonary immunity in man.
In mice intranasal immunisation with the subunit Mtb vaccine, Ad85A, generates pulmonary immunity. Importantly, Mtb growth is inhibited immediately after challenge. In contrast, parenteral BCG or subunit vaccines only inhibit Mtb growth late after challenge. The additive effect of parenteral/pulmonary immunisation does not depend on prime/boosting but on targeting early and late Mtb growth. Therefore SIM should be possible. We have demonstrated in practice that it is highly effective.
We will determine the efficacy, duration and mechanism of protection of SIM. SIM safety will be tested by assessing immune responses and pathology after coincident infection with influenza virus or induction of allergic lung responses.
Expression of the chemokine/receptor pair CXCL16/CXCR6 in the lungs after pulmonary immunisation is a correlate of protective pulmonary immunity. CXCR6+ cells are recoverable in bronchoalveolar lavage (BAL) unlike antigen specific cells induced by parenteral vaccines. However, three cell populations take part in pulmonary protection against Mtb, BAL cells, interstitial lung cells and extrapulmonary lymphocytes, but their roles in early and late inhibition of Mtb growth after challenge are ill-defined, as is the function of CXCL16/CXCR6 in intrapulmonary localization of cells. We shall use in vivo antibody depletion/blocking or transfer of purified cells to determine the function of different cells in early or late growth inhibition and the migration inhibitor, fingolimod, to dissect the contribution of intrapulmonary and extrapulmonary cells. CXCL16/CXCR6 deficient mice will illuminate the role of these molecules.
We will develop assays for human pulmonary immunity by quantifying immune mediators in nasal and bronchial fluid or supernatants of cultured nasal epithelial cells, BAL or peripheral blood lymphocytes from Mtb un-exposed, Mtb exposed, latently infected subjects or Tb patients.
This project will establish SIM as a highly effecive and safe method, which would require only a single clinic visit. We will determine the roles of different Tb-immune populations in protective lung immunity and the roles of CXCL16/CXCR6 in localization of cells within the lung. We will identify candidate assays for future assessment of immunity after pulmonary immunisation in man.