Development and Evaluation of a Fusion Polyprotein Based on HspX and Other Antigen Sequences for the Serodiagnosis of Tuberculosis

Abstract

BackgroundThe lack of suitable diagnostic tools contributes to the high prevalence of tuberculosis (TB) worldwide. Serological tests, based on multiple target antigens, represent an attractive option for diagnosis of this disease due to their rapidity, convenience, and low cost.MethodsMeasures to reduce non-specific reactions and thereby improve the specificity of serological tests were investigated, including blocking antibodies against common bacteria in serum samples and synthesizing polypeptides covering non-conserved dominant B-cell epitopes of antigens. In addition, a fusion polyprotein containing HspX and eight other antigen sequences was constructed and expressed to increase overall sensitivity of the tests.ResultsInclusion of Escherichia coli lysate partially increased the specificity of the serological tests, while synthesis and inclusion of peptides containing non-conserved sequences of TB antigens as well as dominant B-cell epitopes reduced non-specific reactions without a decrease in sensitivity of the tests. A polyprotein fusing HspX and eight other antigen sequences was constructed and displayed 60.2% sensitivity, which was higher than that of HspX and the other individual antigen segments. Moreover, the specificity of the polyprotein was 93.8%, which was not significantly decreased when compared with HspX and the other individual antigen segments.ConclusionsThe roles of the fusion polyprotein in the humoral immune response against TB infection were demonstrated and provide a potential novel approach for the development of TB diagnostics.

Nano-Sized Chimeric Human Papillomavirus-16 L1 Virus-like Particles Displaying Mycobacterium tuberculosis Antigen Ag85B Enhance Ag85B-Specific Immune Responses in Female C57BL/c Mice

“…Although an effective Th1-type cell-mediated adaptive immune response characterized by the secretion of IFN-γ and TNF via antigen-specific CD4 T cells is known to be required, it is not sufficient to provide protective immunity against TB. For example, numerous studies indicated that humoral immunity also plays an important role in anti-TB immunity [ 35 , 36 , 37 ]. In view of the complexity of TB–host interactions, the mechanism related to the immune response to TB is still poorly understood.…”

Serological analysis reveals differential antibody responses between TB patients and latently infected individuals from the TB endemic country of Mozambique

“…Nevertheless, there is a renewed effort to improve on serodiagnosis of TB by either combining different tests (4), or combining multiple antigens or epitopes of Mtb (4)(5)(6)(7)(8)(9)(10)(11)(12), with some of the reports claiming discriminatory potential between active TB and LTBI (6,7,9,10). In this study, we performed an exploratory study on a historic set of serum samples from TB patients, LTBI and healthy (BCG vaccinated) controls in Mozambique, collected between 2016 and 2018 as part of a wider study [ (13,14) the EMI-TB project].…”