Detection of anti-HspX antibodies and HspX protein in patient sera for the identification of recent latent infection by Mycobacterium tuberculosis

Abstract

Mycobacterium tuberculosis is a pathogen causing tuberculosis (TB) a spectrum of disease including acute and asymptomatic latent stages. Identifying and treating latently-infected patients constitutes one of the most important impediments to TB control efforts. Those individuals can remain undiagnosed for decades serving as potential reservoirs for disease reactivation. Tests for the accurate diagnosis of latent infection currently are unavailable. HspX protein (α-crystallin), encoded by Rv2031c gene, is produced in vitro by M. tuberculosis during stationary growth phase and hypoxic or acidic culture conditions. In this study, using standard, and Luminex xMAP® bead capture ELISA, respectively, we report on detection of anti-HspX IgG and IgM antibodies and HspX protein in sera from acute and latent TB patients. For the antibody screen, levels of IgG and IgM antibodies were similar between non-infected and active TB patients; however, individuals classified into the group with latent TB showed higher values of anti-HspX IgM (p = 0.003) compared to active TB patients. Using the bead capture antigen detection assay, HspX protein was detected in sera from 56.5% of putative latent cases (p< 0.050) compared to the background median with an average of 9,900 pg/ml and a range of 1,000 to 36,000 pg/ml. Thus, presence of anti-HspX IgM antibodies and HspX protein in sera may be markers of latent TB.

Immune responses to Mycobacterium tuberculosis membrane-associated antigens including alpha crystallin can potentially discriminate between latent infection and active tuberculosis disease

“…We encountered a similar phenomenon in this study, which resulted in 'negative' (< 0) ΔOD values for anti-Acr IgM antibodies. This observation was in complete contrast to some of the earlier studies which have shown high levels (OD >1.5) of anti-Acr IgM antibodies in ATB patients as well as healthy contacts [29,32,45,50]. Apart from the demographic differences in study populations, such discrepant results may also occur due to purely technical reasons.…”

“…Two of them have reported that IgA and IgG levels are higher in patients than in contacts or healthy subjects [29,30] and one study has reported that children with TB have higher IgG and IgM levels as compared to healthy children [31]. Another study has found that the level of anti-Acr IgM is significantly higher in LTBI than in active TB [32].…”

Metabolic Changes of Mycobacterium tuberculosis during the Anti-Tuberculosis Therapy

“…Regarding the HspX protein, its increased representation in the 3955 strain compared to RUS_B0, which went down in the strain 2093, was observed. Previously, it was proposed that HspX can be used as a marker of the disease, including its latent form [21,22]. A reduced representation of this protein in the resistant strain casts doubts on its usefulness.…”

<p>Structural switching electrochemical DNA aptasensor for the rapid diagnosis of tuberculous meningitis</p>

“…HspX is a Mycobacterium tuberculosis antigen (also known as α-crystallin) which is abundantly expressed under hypoxia 3,14 and in both active and latent forms of TB. 3,14,16 The utility of this antigen in the antibody-based diagnosis of pulmonary TB has already been established. [17][18][19] In another study, the detection of HspX messenger RNA was used to detect viable M. tuberculosis directly in sputum specimens from clinically suspected TB patients.…”