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Immunization with the recombinant PorB outer membrane protein induces a bactericidal immune response against
J Claire Wright1, Jeannette N Williams, Myron Christodoulides
1Molecular Microbiology and Infection, Division of Infection, Inflammation and Repair, University of Southampton Medical School, and Southampton General Hospital, United Kingdom.
Abstract:
Infections with Neisseria meningitidis are characterized by life-threatening meningitis and septicemia. The meningococcal porin proteins from serogroup B meningococci have been identified as candidates for inclusion in vaccines to prevent such infections. In this study, we investigated the vaccine potential of the PorB porin protein free of other meningococcal components. The porB gene from a strain of Neisseria meningitidis expressing the class 3 outer membrane porin protein (PorB3) was cloned into the pRSETB vector, and the protein was expressed at high levels in a heterologous host Escherichia coli. The recombinant protein was purified to homogeneity by affinity chromatography and used for immunization after incorporation into liposomes and into micelles composed either of zwitterionic detergent or nondetergent sulfobetaine. The immunogenicity of these preparations was compared to recombinant PorB protein adsorbed to Al(OH)(3) adjuvant as a control. Although sera raised against the protein adsorbed to Al(OH)(3) reacted with the purified recombinant protein, sera raised against liposomes and micelles showed greater activity with native protein, as measured by enzyme immunoassay with outer membranes and by whole-cell immunofluorescence. Reactivity with native protein was considerably enhanced by incorporation of the adjuvant monophosphoryl lipid A into the liposome or micelle preparations. Recognition of the native protein was in a serotype-specific manner and was associated with the ability of the antisera to promote high levels of serotype-specific complement-mediated killing of meningococci. These results demonstrate that the PorB protein should be considered as a component of a vaccine designed to prevent serogroup B meningococcal infection.
Insights
This study explored the vaccine potential of Neisseria meningitidis PorB protein. Formulations with liposomes and micelles, especially with monophosphoryl lipid A, showed enhanced immunogenicity against serogroup B meningococci.
Area of Science:
- Immunology
- Microbiology
- Vaccine Development
Background:
- Neisseria meningitidis serogroup B causes life-threatening meningitis and septicemia.
- Meningococcal porin proteins are vaccine candidates for preventing these infections.
Purpose of the Study:
- To investigate the vaccine potential of the PorB porin protein, isolated from other meningococcal components.
- To compare the immunogenicity of PorB protein formulated in liposomes and micelles versus aluminum hydroxide adjuvant.
Main Methods:
- Cloned the porB gene from Neisseria meningitidis into Escherichia coli for recombinant protein expression.
- Purified the recombinant PorB protein and formulated it into liposomes and micelles.
- Assessed immunogenicity by comparing antibody reactivity to native meningococcal proteins and complement-mediated killing.
Main Results:
- Liposome and micelle formulations, particularly with monophosphoryl lipid A, showed greater reactivity with native meningococcal proteins compared to aluminum hydroxide adjuvant.
- Antisera promoted significant serotype-specific complement-mediated killing of meningococci.
- Antibody recognition was serotype-specific.
Conclusions:
- The PorB protein is a promising candidate for a serogroup B meningococcal vaccine.
- Liposomal and micellar formulations enhance the immunogenicity of the PorB protein.
- Monophosphoryl lipid A incorporation further boosts immune responses against native meningococcal proteins.