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Infection and Immunity, February 2001, p. 949-958, Vol. 69, No. 2
MedImmune, Inc., Gaithersburg, Maryland
20878,1 and Pediatric Infectious Disease
Unit, Soroka University Medical Center and the Faculty of Health
Sciences, Ben-Gurion University, Beer-Sheva 84101, Israel2
Received 24 August 2000/Returned for modification 30 October
2000/Accepted 15 November 2000
Four pneumococcal genes (phtA, phtB, phtD, and
phtE) encoding a novel family of homologous proteins (32 to
87% identity) were identified from the Streptococcus
pneumoniae genomic sequence. These open reading frames were
selected as potential vaccine candidates based upon their possession of
hydrophobic leader sequences which presumably target these proteins to
the bacterial cell surface. Analysis of the deduced amino acid
sequences of these gene products revealed the presence of a histidine
triad motif (HxxHxH), termed Pht (pneumococcal histidine triad) that is
conserved and repeated several times in each of the four proteins. The
four pht genes (phtA, phtB, phtD, and a
truncated version of phtE) were expressed in
Escherichia coli. A flow cytometry-based assay confirmed
that PhtA, PhtB, PhtD and, to a lesser extent, PhtE were detectable on
the surface of intact bacteria. Recombinant PhtA, PhtB, and PhtD
elicited protection against certain pneumococcal capsular types in a
mouse model of systemic disease. These novel pneumococcal antigens may
serve as effective vaccines against the most prevalent pneumococcal serotypes.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.2.949-958.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Identification and Characterization of a Novel
Family of Pneumococcal Proteins That Are Protective against
Sepsis

*
Corresponding author. Mailing address: MedImmune, Inc.,
25 W. Watkins Mill Rd., Gaithersburg, MD 20878. Phone: (301) 527-4309. Fax: (301) 527-4214. E-mail: adamouje{at}medimmune.com.
Present address: Pathogenesis Corp., Seattle, WA 98119.
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