Immunization with the Haemophilus ducreyi Hemoglobin Receptor HgbA with Adjuvant Monophosphoryl Lipid A Protects Swine from a Homologous but Not a Heterologous Challenge

Abstract

Haemophilus ducreyi, the etiological agent of chancroid, has a strict requirement for heme, which it acquires from its only natural host, humans. Previously, we showed that a vaccine preparation containing the native hemoglobin receptor HgbA purified from H. ducreyi class I strain 35000HP (nHgbA I ) and administered with Freund's adjuvant provided complete protection against a homologous challenge. In the current study, we investigated whether nHgbA I dispensed with monophosphoryl lipid A (MPL), an adjuvant approved for use in humans, offered protection against a challenge with H. ducreyi strain 35000HP expressing either class I or class II HgbA (35000HPhgbA I and 35000HPhgbA II , respectively). Pigs immunized with the nHgbA I /MPL vaccine were protected against a challenge from homologous H. ducreyi strain 35000HPhgbA I but not heterologous strain 35000HPhgbA II , as evidenced by the isolation of only strain 35000HPhgbA II from nHgbA I -immunized pigs. Furthermore, histological analysis of the lesions showed striking differences between mock-immunized and nHgbA I -immunized animals challenged with strains 35000HPhgbA I but not those challenged with strain 35000HPhgbA II . Mock-immunized pigs were not protected from a challenge by either strain. The enzyme-linked immunosorbent assay (ELISA) activity of the nHgbA I /MPL antiserum was lower than the activity of antiserum from animals immunized with the nHgbA I /Freund's vaccine; however, anti-nHgbA I from both studies bound whole cells of 35000HPhgbA I better than 35000HPhgbA II and partially blocked hemoglobin binding to nHgbA I . In conclusion, despite eliciting lower antibody ELISA activity than the nHgbA I /Freund's, the nHgbA I /MPL vaccine provided protection against a challenge with homologous but not heterologous H. ducreyi, suggesting that a bivalent HgbA vaccine may be needed.

Identification and analysis of three virulence-associated TonB-dependent outer membrane receptors of Pseudomonas fluorescens

“…For example, immunoproteomic analysis of the whole cell proteins of Riemerella antipestifer revealed that TonB-dependent receptor was among the immunogenic outer membrane proteins (Q. , and a study with a Znuptake Tdr, ZnuD, of Neisseria meningitidis showed that it could induce bactericidal antibodies upon immunization of mice (Stork et al 2010). Similarly, Tdr with vaccine potentials have been found in Haemophilus ducreyi and, as reported by us, P. fluorescens (Afonina et al 2006, Fusco et al 2010, Leduc et al 2011, Y. Hu et al 2012. In this study, we found that, when used as subunit vaccines, the recombinant proteins rTdr1, rTdr2, and rTdr3 elicited moderate but significant protections that differed in magnitude, with the highest RPS being effected by rTdr3.…”

Rapid Divergence of Two Classes of Haemophilus ducreyi

“…For example, a monovalent HgbA vaccine has shown promise in a pig model, where immunization with class I HgbA (HgbA I ) and Freund's adjuvant provided protection against a challenge with class I strains (1). However, immunization with HgbA I and monophosphoryl lipid A, an adjuvant approved for use in humans, resulted in protection against class I strains but not class II strains (13). This is not surprising, given the differences in the HgbA sequences in class I and II strains (45).…”

Passive Immunization with a Polyclonal Antiserum to the Hemoglobin Receptor of Haemophilus ducreyi Confers Protection against a Homologous Challenge in the Experimental Swine Model of Chancroid

“…H. ducreyi strain 35000HP is the human-passaged variant (4) of wild-type isolate 35000 (14) and the prototypical strain for H. ducreyi class I strains (48). Strain FX547 is an isogenic hgbA deletion mutant of strain 35000HP (26), and FX548, an isogenic 35000HP strain in which the hgbA gene was replaced with hgbA of strain DMC111, a class II H. ducreyi strain (13). In this report, H. ducreyi strains 35000HP, FX547, and FX548 are designated 35000HPhgbA I , 35000HP⌬hgbA, and 35000HPhgbA II , respectively.…”

“…Previous studies have shown that active immunization with a native preparation of HgbA purified from H. ducreyi prototypical class I strain 35000HP (nHgbA I ) protects against a homologous challenge in the experimental swine model of chancroid (1,13). Protection was observed when using either Freund's adjuvant or an adjuvant approved for use in humans, monophosphoryl lipid A (MPL).…”