A. Frisk et al., LOCALIZATION AND IMMUNOLOGICAL PROPERTIES OF A 24-KDA SURFACE PROTEINOF HAEMOPHILUS-DUCREYI, Journal of Medical Microbiology, 43(3), 1995, pp. 192-200
The cell wall and outer structures of Haemophilus ducreyi bacteria wer
e investigated. The 24-kDa outer protein from two strains was purified
with an SDS-PAGE preparative continuous-elution electrophoresis cell.
The protein was further characterised by SDS-PAGE and immunoblotting,
and the immunological properties were investigated by ELISA. Localisa
tion on the bacterial surface was investigated by immune-electronmicro
scopy with a polyclonal antiserum raised against the purified protein.
A triple-laminar cell wail typical of gram-negative bacteria, close c
ellular contact between bacterial cells and outer blebs were seen on t
hin sections. An additional high mel. wt band of c. 165 kDa was seen w
hen not treated by heating to 100 degrees C. A high density fibrilla-l
ike material was detected on the bacterial cell and in the environment
by negative staining and immune-electronmicroscopy with antisera spec
ific for the 24-kDa protein. The surface localisation of the 24-kDa pr
otein was confirmed by an ELISA technique with the specific antiserum
and whole bacterial cells as antigen. The presence of antibodies to th
e 24-kDa protein was demonstrated in antisera to 13 strains of H. ducr
eyi, indicating antigenic identity or within-species crossreactivity.
Low titres of antibodies to this protein were also detected in 19 anti
sera raised against different strains of gram-negative bacteria, indic
ating cross-reactivity with other species. Antibody response to the 24
-kDa protein in rabbits immunised subcutaneously with live bacteria re
sulted in a secondary IgG response. Of 28 sera from patients with cult
ure-verified chancroid, 26 manifested high titres of IgG antibodies to
the 24-kDa protein, thus indicating the involvement of this antigen i
n the disease process in man.