title: Recombinant outer membrane vesicles carrying Chlamydia muridarum HtrA induce antibodies that neutralize chlamydial infection in vitro.
abstract: BACKGROUND
  Outer membrane vesicles (OMVs) are spheroid particles released by all Gram-negative bacteria as a result of the budding out of the outer membrane. Since they carry many of the bacterial surface-associated proteins and feature a potent built-in adjuvanticity, OMVs are being utilized as vaccines, some of which commercially available. Recently, methods for manipulating the protein content of OMVs have been proposed, thus making OMVs a promising platform for recombinant, multivalent vaccines development.
  
  
  METHODS
  Chlamydia muridarum DO serine protease HtrA, an antigen which stimulates strong humoral and cellular responses in mice and humans, was expressed in Escherichia coli fused to the OmpA leader sequence to deliver it to the OMV compartment. Purified OMVs carrying HtrA (CM rHtrA-OMV) were analyzed for their capacity to induce antibodies capable of neutralizing Chlamydia infection of LLC-MK2 cells in vitro.
  
  
  RESULTS
  CM rHtrA-OMV immunization in mice induced antibodies that neutralize Chlamydial invasion as judged by an in vitro infectivity assay. This was remarkably different from what observed with an enzymatically functional recombinant HtrA expressed in, and purified from the E. coli cytoplasm (CM rHtrA). The difference in functionality between anti-CM rHtrA and anti-CM rHtrA-OMV antibodies was associated to a different pattern of protein epitopes recognition. The epitope recognition profile of anti-CM HtrA-OMV antibodies was similar to that induced in mice during Chlamydial infection.
  
  
  CONCLUSIONS
  When expressed in OMVs HtrA appears to assume a conformation similar to the native one and this results in the elicitation of functional immune responses. These data further support the potentiality of OMVs as vaccine platform.
authors.affiliation: Novartis Vaccines and Diagnostics, Siena, Italy.
authors.forename: Erika
authors.initials: E
authors.lastname: Bartolini
authors.forename: Elvira
authors.initials: E
authors.lastname: Ianni
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Frigimelica
authors.forename: Roberto
authors.initials: R
authors.lastname: Petracca
authors.forename: Giuliano
authors.initials: G
authors.lastname: Galli
authors.forename: Francesco
authors.initials: F
authors.lastname: Berlanda Scorza
authors.forename: Nathalie
authors.initials: N
authors.lastname: Norais
authors.forename: Donatello
authors.initials: D
authors.lastname: Laera
authors.forename: Fabiola
authors.initials: F
authors.lastname: Giusti
authors.forename: Andrea
authors.initials: A
authors.lastname: Pierleoni
authors.forename: Manuela
authors.initials: M
authors.lastname: Donati
authors.forename: Roberto
authors.initials: R
authors.lastname: Cevenini
authors.forename: Oretta
authors.initials: O
authors.lastname: Finco
authors.forename: Guido
authors.initials: G
authors.lastname: Grandi
authors.forename: Renata
authors.initials: R
authors.lastname: Grifantini
keywords: Chlamydia; Chlamydia trachomatis; DO serine protease; neutralizing antibodies; outer membrane vesicles