A similar model of influenza challenge showed that ablation of the NALT had no effect on T-cell recruitment, serum or nasal cavity IgG and IgA levels or on the speed at which the virus was cleared [15]. However, in contrast, an intra-nasal model of reovirus infection showed the NALT to be the inductive site of both humoral and cellular immune responses [11] and in another I-BET151 cost influenza virus model, depletion of T-cells prior to virus challenge, increased viral load in both the lungs and nose, implying that T-cells restrict viral

replication in both sites [16]. It was therefore of interest to assess the role of the NALT in protection induced by the viral vectored vaccine candidate Ad85A against another respiratory pathogen, M.tb. We and others have previously shown that i.n. immunisation with Ad85A in 50 μl gives protection against

M.tb challenge comparable to parenteral immunisation with BCG ( Fig. 2A and B) [4] and [9]. Here we compared the protection afforded by identical numbers of Ad85A v.p. delivered in 5–6 or 50 μl i.n. The results show that immunisation in 5–6 μl provides no protection against aerosol challenge with M.tb ( Fig. 2), despite a weak antigen-specific response in the lung ( Fig. 1). Immunisation with 5–6 μl i.n. does however induce a NALT response comparable to 50 μl ( Fig. 1A). These data indicate that the magnitude of the response in the lung, but not in the NALT, correlates with protection. Indeed, a preliminary experiment in which Ad85A was delivered directly into the trachea (i.t.), find more thus bypassing the NALT, indicated that this regime protected from BCG challenge to a level comparable to 50 μl i.n. immunisation. Assessment of the T-cell phenotypes generated by the 5–6 or 50 μl inocula showed that the number of CD8+ cells in the lung producing unless IL-2 was greater after immunisation with 50 μl, as was the number producing TNFα, although the greatest difference was in the total producing IFNγ (Fig. 3A).

Since it has been suggested that the quality of the T-cell response plays an important role in the response to pathogens such as HIV, malaria and M.tb, with the proportion of T-cells producing more than one cytokine correlating with protection [23], [24], [27] and [28], we measured the proportions of lung CD8+ T-cells induced by immunisation with 5–6 or 50 μl producing one, two or all three of IFNγ, IL-2 and TNFα ( Fig. 3C). Despite being the protective regime, it appears that immunisation with 50 μl induces more single cytokine producing cells (1+) than with 5–6 μl ( Fig. 3C), the main difference being in the number IFNγ-only producing cells ( Fig. 3C). Therefore it is likely that a high proportion of multi-cytokine producing cells is not necessary for protection in this model.