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Updated: Aug 19, 2026
Bone Marrow-derived Macrophage Production
Published on: November 22, 2013
HspX is present within Mycobacterium paratuberculosis-infected macrophages and is recognized by sera from some
1National Animal Disease Center, ARS-USDA, Ames, IA 50010, USA. jbannant@nadc.ars.usda.gov
Abstract:
A portion of the gene encoding HspX has been previously identified as a sequence specific to Mycobacterium avium subspecies paratuberculosis (hereafter referred to as M. paratuberculosis) based on DNA hybridization experiments. In this study, rabbit antisera were raised against a recombinant protein of HspX fused to the Escherichia coli maltose binding protein (MBP/HspX). Immunoblots of lysates of M. paratuberculosis-infected macrophages probed with the rabbit antisera showed that HspX was present within infected macrophages of bovine and murine origin. This observation was confirmed by immunofluorescence microscopy of infected macrophages. Lysates of E. coli expressing HspX without the MBP fusion partner were loaded onto preparative SDS-PAGE gels and used to determine whether infected cattle generated a humoral immune response to the antigen. Sera from four of 24 paratuberculous cows (17%) detected HspX. No reactivity was present in sera from control cows. While HspX may be immunogenic during infection in some cows, the protein is not secreted and it does not stimulate cell-mediated immunity. Collectively, these data give a preliminary characterization of the first described M. paratuberculosis protein identified within infected macrophages.
Insights
Researchers identified the Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) HspX protein within infected macrophages. Some infected cattle showed an immune response to HspX, though it is not secreted or cell-mediated.
Area of Science:
- Microbiology
- Immunology
- Veterinary Science
Background:
- A DNA sequence specific to Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) was previously identified.
- HspX is a protein encoded by a portion of the M. paratuberculosis gene.
Purpose of the Study:
- To characterize the M. paratuberculosis HspX protein.
- To determine if HspX is present in infected macrophages.
- To investigate the humoral immune response to HspX in infected cattle.
Main Methods:
- Raised rabbit antisera against a recombinant M. paratuberculosis HspX protein.
- Used immunoblots and immunofluorescence microscopy to detect HspX in infected bovine and murine macrophages.
- Analyzed sera from paratuberculous and control cows for reactivity to HspX using SDS-PAGE.
Main Results:
- HspX was detected within M. paratuberculosis-infected macrophages from cattle and mice.
- Sera from 17% of infected cattle recognized HspX, while control sera did not.
- HspX is not secreted and does not stimulate cell-mediated immunity.
Conclusions:
- HspX is the first described M. paratuberculosis protein found within infected macrophages.
- HspX may be immunogenic in some cattle during M. paratuberculosis infection.
- Further characterization of HspX is warranted.
