Outer membrane protein D15 is conserved among Haemophilus influenzae species and may represent a universal protective antigen against invasive disease.
We have cloned and sequenced the d15 gene from two strains of Haemophilus influenzae type b (Hib) and two strains of nontypeable H. influenzae (NTHI). The nucleotide and deduced protein sequences of d15 are highly conserved, with only a small variable region identified near the carboxyl terminus of the protein. Analysis of upstream sequences revealed that the H. influenzae d15 gene may be part of a large potential operon of closely spaced open reading frames, including one with significant homology to the Escherichia coli cds gene encoding CDP-diglyceride synthetase. Southern blot analysis demonstrated that the d15 gene is also present in H. influenzae types a, c, d, e, and f and in Haemophilus parainfluenzae. A recombinant D15 (rD15) protein was expressed in good quantity in E. coli from the inducible T7 promoter, and monospecific anti-rD15 antibodies were raised. Immunoblot analysis of H. influenzae serotypes a, b, c, d, e, and f, NTHI, and H. parainfluenzae lysates revealed that they all expressed a cross-reactive D15-like protein. Purified rD15 was found to be highly immunogenic in mice, guinea pigs, and rabbits, and passive transfer of anti-rD15 antibodies protected infant rats from challenge with H. influenzae type b or type a in infant rat models of bacteremia. Thus, D15 is a highly conserved antigen that is protective in animal models and it may be a useful component of a universal subunit vaccine against Haemophilus infection and disease.
Loosmore
S M
SM
Research Centre, Pasteur Merieux Connaught Canada, North York, Ontario, Canada. sloosmore@ca.pmc-vacc.com
Yang
Y P
YP
Coleman
D C
DC
Shortreed
J M
JM
England
D M
DM
Klein
M H
MH
D000595:Amino Acid Sequence; D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry*; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000276:immunology*; D001483:Base Sequence; D015153:Blotting, Western; D003001:Cloning, Molecular; D004926:Escherichia coli; D006168:Guinea Pigs; D006193:Haemophilus influenzae / Q000737:chemistry / Q000235:genetics / Q000276:immunology*; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D011817:Rabbits; D011994:Recombinant Proteins / Q000276:immunology; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012703:Serotyping
D000942:Antigens, Bacterial; D001425:Bacterial Outer Membrane Proteins; C093356:D15 antigen, bacteria; D011994:Recombinant Proteins