Abstract
Streptococcus pneumoniae (pneumococcus) is a leading cause of pneumonia, meningitis, and sepsis in children around the world. Recent estimates show that approximately 400,000 children under the age of five die annually from infections caused by S. pneumoniae. Pneumococcal Surface Protein A (PspA) is a well-characterized antigen, that confers protection in animal models, and represents a good alternative for current conjugate vaccines. Induction of protective immune responses directed to PspA in animal models has already been described, but few low cost adjuvants for the composition of a subunit vaccine have been proposed to date. In previous studies, our group tested the use of the whole cell pertussis vaccine (wP) produced at the Butantan Institute, as adjuvant, in combination with PspA. The wP vaccine is one of the components of the DTP (diphtheria, tetanus, pertussis) vaccine given to Brazilian children by the Ministry of Health at 2, 4 and 6 months of age, with a booster at 18 months and 5 years. Nasal immunization of BALB/c mice with a combination of PspA and wP induced high levels of anti-PspA antibodies and conferred protection against lethal challenges and nasopharyngeal colonization with S. pneumoniae. In the master project we proposed the expression of PspA in the B. pertussis vaccine, in order to produce an inactivated recombinant whole cell vaccine (wPPspA). The N-terminal portion of PspA was expressed as a fusion with the N-terminal portion of the FHA (Filamentous hemagglutinin A) antigen of B. pertussis. Some clones were tested for mouse immunization and, although inducing low levels of anti-PspA antibodies, a significant increase in the survival of the animals after a lethal challenge with pneumococci was observed. Based on these promising results, we propose continuing the studies during the doctorate. To do so, a modification in the fha gene sequence is proposed with the aim of improving the expression of the FHA44:PspA4 protein in the wPPspA vaccine. Expression of a FHA44:PspA4 fusion protein in E. coli system will also be performed with the aim of testing this recombinant protein as an immunogen, in addition to dose-boosting protocols using the wPPspA and FHA44:PspA4 vaccines. Finally, a novel approach based on the adjuvant properties of B. pertussis adenylate cyclase toxin (CyaA) will also be studied. This system utilizes the ability of CyaA to bind to receptors present on antigen presenting cells. As a result, CyaA is expected to direct the presentation of PspA to the immune system, increasing the response against this protein. (AU)
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