J. 12 h postchallenge, vaccinated mice Edg1 displayed higher numbers of CD4+ T, CD8+ T, and B lymphocytes in the lungs. However, protection still occurs in the absence of each of these cells during the challenge, indicating that other effectors may be related to the prevention of lung injuries in this model. High levels of mucosal anti-PspA antibodies were maintained in vaccinated mice during the challenge, suggesting an important role in protection. INTRODUCTION is the main etiological agent of DM1-SMCC bacterial pneumonia, meningitis, and sepsis and can be of great importance, especially in children from developing countries. Every year, 1 million deaths of children under 5 years occur due to pneumococcal diseases (39). Current vaccines are composed of polysaccharides (PS) from different serotypes conjugated to protein carriers. Acquired immunity is achieved through the induction of anti-PS antibodies, protecting vaccinated children against colonization and invasive pneumococcal diseases caused by the serotypes included in the formulations (8, 46). The induction of serotype-specific protection is an important issue to be considered, since variation in the prevalent serotypes (from more than 90 serotypes described) among different regions of the world is observed (13, 23, 49). Several proposals of new vaccines are based on conserved antigens that could confer protection against virtually all pneumococcal serotypes (10, 30, 32, 37, 40C42). These vaccines also have emerged as a way to avoid a possible consequence related to the massive use of the conjugated vaccines, that is, the replacement of the prevalent serotypes by others not included in the formulations (17, 56). Depending on the composition, the new vaccines can DM1-SMCC confer protection in mouse models of pneumococcal infection by the induction of specific antibodies and/or cellular immune responses (31). In an experimental pneumococcal carriage study in humans, McCool and collaborators reported a significant rise in serum IgG against the pneumococcal surface protein A (PspA) (35). Different immunization strategies and animal models were used to confirm PspA as a good vaccine candidate (4, 12, 36, 57). This antigen has already undergone a phase I clinical trial and was shown to be immunogenic in humans (38). Sera from immunized subjects were able to passively protect mice against pneumococcal lethal challenges with different serotypes (11). PspA is expressed by all pneumococcal isolates, but the N-terminal region of the molecule, which contains protective epitopes, is highly variable. Sequencing analyses led to the classification of PspAs in 6 clades that can be grouped into three families (26). Cross-reactivity was reported for molecules that belong to the same family or for specific molecules that induce antibodies that recognize PspAs from different clades (18). Broad-coverage vaccines based on PspA would thus depend on the use of more than one molecule or on the choice of specific PspA molecules (37). In animal models, protection elicited by vaccines composed of PspA is often accompanied by the induction of high levels of specific antibodies (10, 22, 24, 44) which, upon binding to pneumococcal surface, promote the deposition of complement (9, 12, 47, 57) and enhance killing by lactoferrin (9, 48). In addition, the use of adjuvants that elicit Th1 immune responses against PspA seems to optimize protection (4, 19, 20). We have previously used the whole-cell pertussis vaccine (wP) as an adjuvant to a nasal vaccine formulated with an N-terminal fragment of PspA from clade 5 (PspA5-wP) (43). As it is composed of whole bacteria, wP can modulate the immune response, inducing a Th1 and/or a Th17 character (7, 25) that may improve responses against combined antigens (6, 51, DM1-SMCC 52). Mice immunized with PspA5-wP were protected against an invasive respiratory challenge with a DM1-SMCC serotype 3 strain (43). Spread of the bacteria to the bloodstream was prevented, probably by the high levels of anti-PspA antibodies observed in vaccinated mice. However, despite the presence of antibodies, complete clearance of bacteria from the lungs occurred only 3 weeks after the challenge, suggesting that immune responses in the respiratory mucosa may contribute to protection (43). The control of inflammatory responses in lungs seems to be an important feature for protection against pneumococcal respiratory invasive challenges in mice (20, 21). Here we have evaluated the mucosal immune responses elicited in lungs of mice vaccinated with PspA5-wP. Infiltration of cells in the respiratory mucosa as well. DM1-SMCC