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The 56-kilodalton major protein antigen of Rickettsia tsutsugamushi: molecular cloning and sequence analysis of the sta56 gene and precise identification of a strain-specific epitope.

ABSTRACT: Lasting immunity against Rickettsia tsutsugamushi, the causative agent of scrub typhus fever, has been demonstrated to be strain specific. Two protein antigens of 110 and 56 kilodaltons (kDa) have been shown to exhibit strain-specific epitopes. The 56-kDa scrub typhus antigen (Sta56) is an abundant outer membrane protein of R. tsutsugamushi and is an antigen often recognized by humans infected with this obligate intracellular bacterium. In this study the complete gene encoding Sta56 (strain Karp) was cloned into pBR322 on a 2.3-kilobase genomic HindIII DNA fragment and the complete 56-kDa polypeptide was expressed in Escherichia coli. DNA sequence analysis of the 2.3-kilobase HindIII fragment revealed an open reading frame large enough to encode a 56-kDa polypeptide. A putative signal sequence was identified at the deduced amino terminus of the Sta56 polypeptide, and pulse-chase analysis of maxicells labeled with [35S]methionine demonstrated that a higher-molecular-weight precursor matures into the 56-kDa polypeptide. Epitope scanning analysis with synthetic peptides derived from the deduced amino acid sequence identified an octapeptide (located from amino acid residues 117 to 124) that was reactive with a Karp strain-specific monoclonal antibody (K13F88A). Other epitopes recognized by different monoclonal antibodies, including another Karp strain-specific monoclone (K1E106), were localized to different regions of the protein based on their reactivities with lambda gt11 recombinants expressing various portions of the sta56 gene.

SUBMITTER: Stover CK

PROVIDER: S-EPMC258779 | biostudies-other | 1990 Jul

REPOSITORIES: biostudies-other

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The 56-kilodalton major protein antigen of Rickettsia tsutsugamushi: molecular cloning and sequence analysis of the sta56 gene and precise identification of a strain-specific epitope.

Stover C K CK Marana D P DP Carter J M JM Roe B A BA Mardis E E Oaks E V EV

Infection and immunity 19900701 7

Lasting immunity against Rickettsia tsutsugamushi, the causative agent of scrub typhus fever, has been demonstrated to be strain specific. Two protein antigens of 110 and 56 kilodaltons (kDa) have been shown to exhibit strain-specific epitopes. The 56-kDa scrub typhus antigen (Sta56) is an abundant outer membrane protein of R. tsutsugamushi and is an antigen often recognized by humans infected with this obligate intracellular bacterium. In this study the complete gene encoding Sta56 (strain Karp ...[more]

PMID: 1694818

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Project description:Orientia tsutsugamushi (Ots) is an obligate, intracellular, mite-transmitted human pathogen which causes scrub typhus. Understanding the diversity of Ots antigens is essential for designing specific diagnostic assays and efficient vaccines. The protective immunodominant type-specific 56 kDa antigen (TSA) of Ots varies locally and across its geographic distribution. TSA contains four hypervariable domains. We bioinformatically analyzed 345 partial sequences of TSA available from India, most of which contain only the three variable domains (VDI-III) and three spacer conserved domains (SVDI, SVDII/III, SVDIII). The total number (152) of antigenic types (amino acid variants) varied from 14-36 in the six domains of TSA that we studied. Notably, 55% (787/1435) of the predicted CD4 T-cell epitopes (TCEs) from all the six domains had high binding affinities (HBA) to at least one of the prevalent Indian human leukocyte antigen (HLA) alleles. A surprisingly high proportion (61%) of such TCEs were from spacer domains; indeed 100% of the CD4 TCEs in the SVDI were HBA. TSA sequences from India had more antigenic types (AT) than TSA from Korea. Overall, >90% of predicted CD4 TCEs from spacer domains were predicted to have HBA against one or more prevalent HLA types from Indian, Korean, Asia-Pacific region or global population data sets, while only <50% of CD4 TCEs in variable domains exhibited such HBA. The phylogenetically and immunologically important amino acids in the conserved spacer domains were identified. Our results suggest that the conserved spacer domains are predicted to be functionally more important than previously appreciated in immune responses to Ots infections. Changes occurring at the TCE level of TSA may contribute to the wide range of pathogenicity of Ots in humans and mouse models. CD4 T-cell functional experiments are needed to assess the immunological significance of these HBA spacer domains and their role in clearance of Ots from Indian patients.

Dataset Information

The 56-kilodalton major protein antigen of Rickettsia tsutsugamushi: molecular cloning and sequence analysis of the sta56 gene and precise identification of a strain-specific epitope.

Publications

The 56-kilodalton major protein antigen of Rickettsia tsutsugamushi: molecular cloning and sequence analysis of the sta56 gene and precise identification of a strain-specific epitope.

Similar Datasets

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