Immunization with the Haemophilus ducreyi trimeric autotransporter adhesin DsrA with alum, CpG or imiquimod generates a persistent humoral immune response that recognizes the bacterial surface

Abstract

The Ducreyi serum resistance A (DsrA) protein of Haemophilus ducreyi belongs to a large family of multifunctional outer membrane proteins termed trimeric autotransporter adhesins responsible for resistance to the bacterial activity of human complement (serum resistance), agglutination and adhesion. The ability of DsrA to confer serum resistance and bind extracellular matrix proteins lies in its N-terminal passenger domain. We have previously reported that immunization with a recombinant form of the passenger domain of DsrA, rNT-DsrA, in complete/incomplete Freund’s adjuvant, protects against a homologous challenge in swine. We present herein the results of an immunogenicity study in mice aimed at investigating the persistence, type of immune response, and the effect of immunization route and adjuvants on surrogates of protection. Our results indicate that a 20 µg dose of rNT-DsrA administered with alum elicited antisera with comparable bacterial surface reactivity to that obtained with complete/incomplete Freund’s adjuvant. At that dose, high titers and bacterial surface reactivity persisted for 211 days after the first immunization. Administration of rNT-DsrA with CpG or Imiquimod as adjuvants elicited a humoral response with similar quantity and quality of antibodies (Abs) as seen with Freund’s adjuvant. Furthermore, intramuscular administration of rNT-DsrA elicited high-titer Abs with significantly higher reactivity to the bacterial surface than those obtained with subcutaneous immunization. All rNT-DsrA/adjuvant combinations tested, save CpG, elicited a Th2-type response. Taken together, these findings show that a 20 µg dose of rNT-DsrA administered with the adjuvants alum, CpG or Imiquimod elicits high-quality Abs with reactivity to the bacterial surface that could protect against an H. ducreyi infection.

The BtaF Adhesin Is Necessary for Full Virulence During Respiratory Infection by Brucella suis and Is a Novel Immunogen for Nasal Vaccination Against Brucella Infection

“…Using the BtaF domain that is exposed on the bacterial cell surface in its native (and trimeric) structure, combined with the appropriate adjuvant (see below), was probably an important factor to achieve a protective immune response against B. suis . In line with this, some proteins from the autotransporter families were shown to be promising antigens for the design of vaccines against other pathogens, including Bordetella pertussis (52, 53), Haemophilus influenza (54), Haemophilus ducreyi (55), Shigella (56), and Enterotoxigenic Escherichia coli (ETEC) (57). In all these cases, a recombinant protein corresponding to the autotransporter passenger domain has been used, reinforcing the potential of this protein family as subunit vaccines.…”

Acetalated Dextran Microparticles for Codelivery of STING and TLR7/8 Agonists

“…Antigen-specific serum antibody-binding titers (endpoint) were determined by a standard ELISA as previously described. 42 Briefly, serial dilutions of test sera were performed in plates coated with OVA (Invivogen) at 2.5 μ g/mL. Following incubation and washing, horseradish-peroxidaseconjugated antimouse Ig-specific antibodies (Southern Biotech, Birmingham, AL) were added to plates at a 1:4000 dilution.…”

Adhesins of Brucella: Their Roles in the Interaction with the Host

“…An essential step in establishing a successful infection is the adhesion of microorganisms to eukaryotic cells, resulting in colonization of the tissue involved. Therefore, the molecules involved in this initial interaction have been widely studied as targets for the development of vaccines against various pathogens such as E. coli [ 100 , 101 ], Haemophilus ducreyi [ 102 ], and Neisseria meningitidis [ 103 , 104 ] among others. Despite the extensive knowledge of adhesins’ role in the pathogenicity of various bacteria, this group of proteins was not studied well in Brucella spp.…”