TITLE:
Synthesis, Characterization, and Immunological Properties of LPS-Based Vaccines Composed of O-Polysaccharides Conjugated with Recombinant Exoprotein A from Pseudomonas aeruginosa
AUTHORS:
Nareman F. Abu-Baker, Hussein Masoud
KEYWORDS:
Pseudomonas aeruginosa, Lipopolysaccharide, Recombinant Exoprotein A, Conjugate Vaccine, Immunization
JOURNAL NAME:
Advances in Microbiology,
Vol.6 No.4,
April
20,
2016
ABSTRACT: Pseudomonas aeruginosa remains one of the major pathogens affecting immunocompromised patients.
LPS-based monovalent (MV) and polyvalent (PV) conjugate vaccines were prepared from
the most prevalent strains of P. aeruginosa International Antigenic Typing Scheme (IATS) 6, 10, 11
and 20 to evaluate their immunogenicity and protective capacities from infection by the pathogens.
Conjugation of the O-polysaccharide (O-PS) antigens of P. aeruginosa strains to the common
immunogenic recombinant Exotoxin A (rEPA) supports the multi-antigenic approach for the development
of a vaccine that provides cross protection against various strains of the pathogen. The
O-PSs were indirectly conjugated through adipic acid dihydrazide (ADH) to rEPA by carbodiimidemediated
condensation reaction. Mice were immunized with the conjugates emulsified with monophosphoryl
lipid A (MPL) or Freund's adjuvant compared with conjugates without adjuvant,
unconjugated mixture of rEPA and O-PS emulsified with MPL, and sterile saline. The MV and PV
vaccines emulsified with MPL adjuvant elicited the highest anti-O-PS IgM and IgG antibodies. Immunization
of mice with MV vaccines derived from IATS 10, 11, and 20, emulsified with MPL adjuvant
provided a high level of protection against the homologous bacterial strain. Similarly, high
protection was obtained when mice were immunized using PV and challenged separately with
bacterial strains 10, 11, and 20, but lower protection against the IATS 6 strain. Also, high cross
protection of MV vaccine derived from O-PS of IATS 10 and 20 was obtained against P. aeruginosa IATS 11 strain. The in vivo protection correlated with the level of anti-O-PS IgG in the mice serum.