Bordetella pertussis and its components as delivery systems and adjuvants for vaccine development against Streptococcus pneumoniae

Abstract

Streptococcus pneumoniae (pneumococcus) is one of the main causes of pneumonia, meningitis and sepsis in children worldwide. Recent estimations show that approximately 400,000 children younger than 5 years old die annually with infections caused by S. pneumoniae worldwide. Pneumococcus surface protein A (PspA) is a well characterized antigen that confers protection in animal models, representing a good alternative for current conjugated vaccines. Induction of protective immune responses directed towards PspA in animal models has already been described, however, few low cost adjuvants for the constitution of subunit vaccines have been proposed. In previous works, our group has tested the whole cell pertussis vaccine (wP), produced at Butantan Institute, as an adjuvant in combination with PspA. The wP vaccine is one of the components of the DTP vaccine (Diphtheria, Tetanus, Pertussis) provided by the Ministry of Health to brazilian children at ages of 2, 4 and 6 months old, with boostersat 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 different challenges with S. pneumoniae. In the master project we have proposed the expression of PspA in the B. pertussis vaccine strain with the aim to produce a recombinant inactivated vaccine (wPPspA). The N-terminal portion of PspA was expressed in fusion with the N-terminal portion of B. pertussis FHA antigen (Filamentous hemagglutinin A). Some clones were selected for immunization of mice and, despite the induction of low levels of anti-PspA antibodies, a significant increase in survival after the lethal challenge with pneumococci was observed in mice immunized with the wPPspA vaccines. Based on these promising results, we propose to further develop the study during the doctorate. In order to do so, it is proposed a modification in the fha gene sequence with the goal to improve the expression of FHA44:PspA4 protein in the wPPspA vaccine. The expression of the fusion protein FHA44:PspA4 in E. coli will also be performed to test the protein as antigen alone as well as in prime-booster protocols using the wPPspA vaccine. Finally, a new approach based on the adjuvant properties of B. pertussis adenylate cyclase toxin (CyaA) will also be studied. This system is based on the ability of CyaA to bind to receptors located in antigen presenting cells. As a result, it is expected that CyaA guides PspA presentation to the immune system, increasing the response against this protein. (AU)