Title Cloning, expression and protective capacity evaluation of two novel B. pertussis vaccine candidates

ALVAREZ HAYES, JIMENA; ERBEN, ESTEBAN; LAMBERTI, YANINA ; GORGOJO, JUAN PABLO .; VALDEZ, HUGO ; PRINCIPI, GUIDO ; MASCHI, FABRICIO ; AYALA, MIGUEL; CARBONE, CECILIA; AND RODRIGUEZ, MARÍA EUGENIA.

Buenos Aires, Argentina

Congreso; SAI; 2010

Bordetella pertussis is the etiologic agent of whooping cough. Despite the high coverage of vaccination, the disease causes more than 500.000 deaths annually worldwide, which is a reflect of the low efficiency of current vaccines. The difference between the infecting phenotype and the phenotype of the vaccine strain may contribute to the lack of protection from the vaccines. Thus, the search of new immunogens expressed by the infecting phenotype may contribute to the development of more efficient vaccines. By immune proteomic, we identified two possible antigens in outer membrane subproteome, named AfuA and IRP1-3, which are over-expressed under iron starvation, a condition that an infecting microorganism face in the host. In the present study, we cloned, expressed and purified both recombinant proteins from Escherichia coli. Mice immunization with AfuA or IRP1-3 led to generation of specific antibodies wich showed phagocytic activity in a two-color flow cytometric assay. Although immunization of BALB/c mice with the recombinat proteins formulated with Freund’s Adjuvant elicited a strong IgG1 response asociated with Th2 type immune response, the sera also showed specific IgG2a antibodies suggesting a Th1 type response contribution, known required for protection against B. pertussis. Accordingly, mice immunized with either AfuA or IRP1-3 alone or in combination were significantly (p<0.01) protected against intranasal infection of B. pertussis. Importantly, the divalent formulation showed a higher protection level (p<0.01), as determined using ANOVA to compare means. Immunoblot analysis demonstrated that both proteins are expressed in clinical isolates grown under iron starvation. Additionally, the presence of antibodies against these proteins in sera from infected individuals, as determined by ELISA, suggests that they are expressed during the infection. Altogether these results point at AfuA and IRP1-3 as promising new candidates to improve the current vaccines.