Rocky mountain spotted fever detection and treatment
Inventors
BOUCHER, Joshua Michael • MESTEK, JR., Anton • MADRID, Clever • BUCH, Jesse Stephen
Assignees
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Publication Number
US-12228578-B2
Publication Date
2025-02-18
Expiration Date
Abstract
Rocky Mountain Spotted Fever (RMSF) is a vector borne disease that is caused by Rickettsia rickettsii infection. It is challenging to identify the disease in dogs and other mammals due to the cross-reacting antibodies from non-pathogenic Rickettsia spp. Provided herein are compositions and methods for detection and treatment of Rocky Mountain spotted fever (“RMSF”). The compositions specifically detect Rickettsia rickettsii and do not cross-react with other Rickettsia species providing rapid and accurate detection and diagnosis of RMSF.
Core Innovation
The invention relates to compositions and polypeptides for Rocky Mountain spotted fever (RMSF) that use Rickettsia rickettsii-specific, non-naturally occurring antigen regions from the SCA2 and VUT proteins. The disclosed antigens include polypeptides derived from SCA2 and VUT-derived peptides, including fusion proteins, and are described with the aim of avoiding cross-reactivity with other Rickettsia species.
The disclosed formats enable detecting anti-Rickettsia rickettsii antibodies or specific binding fragments using immunoassay designs that involve contacting a test sample with one or more of the described polypeptides. The document describes detecting complexes formed between anti-R. rickettsii antibodies and the immobilized polypeptides, including indirect or direct immunoassay formats, supports such as barcoded magnetic beads, secondary antibodies, detector polypeptides, and multiplex immunoassays.
The invention also describes diagnostic kit formats and diagnostic criteria for RMSF detection, including example results and performance characteristics. It further describes multiplex detection of PDX7/TDX1779/TDX1780 with sensitivity in early days post infection and high specificity versus sera positive for other tickborne pathogens, and provides diagnostic criteria based on detecting antibody-polypeptide complexes.
Claims Coverage
The independent claims cover four inventive features: defined sequence-identity antigen polypeptides and fusion constructs, detection of anti-Rickettsia rickettsii antibody-polypeptide complexes, diagnosis of disease caused by Rickettsia rickettsii using the same framework, and a PDX6/PDX73-region polypeptide composition with an epitope tag and/or secretory signal.
Sequence-identity polypeptides and fusion constructs for defined RMSF antigens
A polypeptide comprising 90% or more sequence identity to the polypeptide as set forth in SEQ ID NO: 3, 4, 5, 6, or 7; and fusion protein embodiments comprising two, three, four, five, six, seven or more polypeptides having 90% or more sequence identity to SEQ ID NO:1, 2, 3, 4, 5, 6, or 7, or at least two polypeptides having 90% or more sequence identity to SEQ ID NO: 3, 4, 5, 6, or 7, or the polypeptide as set forth in SEQ ID NO:1 or 2.
Detecting anti-Rickettsia rickettsii antibody-polypeptide complexes with defined SEQ ID polypeptides
A method of detecting anti-Rickettsia rickettsii antibodies or specific binding fragments thereof comprising contacting a test sample with one or more polypeptides as set forth in SEQ ID NO:1, 2, 3, 4, 5, 6, or 7 and detecting complexes of anti-Rickettsia rickettsii antibodies or specific binding fragments thereof and the one or more polypeptides.
Diagnosing Rickettsia rickettsii disease by detecting antibody-polypeptide complexes
A method for diagnosing a disease caused by Rickettsia rickettsii in a subject by contacting a test sample with one or more polypeptides as set forth in SEQ ID NO:1, 2, 3, 4, 5, 6, or 7 and detecting complexes of anti-Rickettsia rickettsii antibodies or specific binding fragments thereof and the one or more polypeptides.
PDX6/PDX73 region polypeptide composition with epitope tag and/or secretory signal
A composition comprising a polypeptide having 90% or more sequence identity to amino acids 21-161 (PDX6×73) of SEQ ID NO:3 and further comprising an epitope tag, a secretory signal, or both an epitope tag and a secretory signal.
Overall, the independent claims define specific sequence-identity antigen polypeptides, including fusion constructs, and use them to form and detect antibody-polypeptide complexes for diagnosing RMSF or a disease caused by Rickettsia rickettsii, with an additional composition-specific claim requiring a PDX6/PDX73-region polypeptide further comprising an epitope tag and/or a secretory signal.
Stated Advantages
Avoiding cross-reactivity with other Rickettsia species.
High specificity versus sera positive for other tickborne pathogens.
Sensitivity in early days post infection.
Documented Applications
Detecting anti-Rickettsia rickettsii antibodies, including in early post-infection windows, using immunoassay and multiplex immunoassay formats with the described polypeptides.
Diagnosing a disease caused by Rickettsia rickettsii (Rocky Mountain spotted fever (RMSF)) in a subject using detection of antibody-polypeptide complexes.
Using multiplex detection including PDX7/TDX1779/TDX1780 and monitoring PDX21 reactivity kinetics in experimentally infected canines.
Diagnostic kit formats for RMSF including polypeptides and reagents enabling binding of the polypeptides to anti-Rickettsia rickettsii antibodies or their specific binding fragments.
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