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Infect. Immun., Dec 1996, 5047-5052, Vol 64, No. 12
TJ Hiltke, AA Campagnari and SM Spinola
Pooled sera from patients with chancroid contain antibodies to a
Haemophilus ducreyi antigen with an approximate molecular weight of 28,000
(28K). Rabbit polyclonal serum that reacts to a 28K protein can be used to
detect H. ducreyi in clinical samples. A monoclonal antibody, designated
5C9, bound to a 28K outer membrane protein and to 35 of 35 H. ducreyi
isolates with diverse geographic origins and did not bind to many species
of the families Pasteurellaceae, Neisseriaceae, and Enterobacteriaceae or
to Corynebacterium and Candida species strains. A 5C9-reactive phage was
recovered from a genomic library, and the gene encoding the 28K protein was
localized to a 626- bp open reading frame, designated hlp, for H. ducreyi
lipoprotein. Translation of hlp predicted a 23K polypeptide that contained
a lipoprotein processing site. Escherichia coli transformed with a plasmid
containing hlp expressed a novel, membrane-associated protein that could be
labeled with [3H]palmitic acid. In H. ducreyi, processing of Hlp was
inhibited by globomycin. Database searches found no homologies to hlp or to
the predicted Hlp amino acid sequence. Restriction enzyme analysis
indicated that hlp was conserved among H. ducreyi isolates. Serum samples
from patients with chancroid and other genital ulcer diseases and from
normal subjects contained antibodies that bound to purified, recombinant
Hlp. Although monoclonal antibody 5C9 recognizes a species-specific epitope
of a unique H. ducreyi lipoprotein, the presence of serum antibodies to Hlp
may not indicate previous infection with H. ducreyi.
Copyright © 1996, American Society for Microbiology
Characterization of a novel lipoprotein expressed by Haemophilus ducreyi
Department of Microbiology and Immunology, Indiana University School of Medicine, Indianapolis 46202, USA.
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