Search

Summary Introduction Accurate, simple and cost-effective diagnostic tests are needed for diagnosis of active tuberculosis (TB). Serodiagnosis is attractive as it can be harnessed for point-of-care tests. Methods We evaluated, in a blinded fashion, the sensitivity and specificity of serologic immunoglobulin (Ig)G, IgA and/or IgM responses to Apa, heat shock protein (HSP) 16.3, HSP20, PE35, probable thiol peroxidase Tpx and lipoarabinomannan (LAM) in 42 HIV-negative South African pulmonary TB patients and 67 control individuals. The status of latent Mycobacterium tuberculosis infection (LTBI) among controls was defined through the TST and IFN-γ release assays (IGRAs). We evaluated 47 definite LTBI (IGRA + /LTBI), 8 putative LTBI (IGRA – /TST + ) and 12 TB-uninfected (non-LTBI) subjects. Results In contrast to anti-PE35 IgA, anti-PE35 IgG and particularly anti-Apa IgA, performances of anti-LAM IgG and selected anti-protein antibodies were less affected by inclusion of LTBI participants into the analysis. Anti-LAM IgG showed with a sensitivity/specificity of 71.4%/86.6% ( p < 0.001) the best discrimination between TB and non-TB subjects. Selected five-antibody-combinations (including anti-LAM IgG, anti-LAM IgA and anti-Tpx IgG) further improved this performance to an accuracy exceeding 86%. Conclusions Antibody responses to some Mycobacterium tuberculosis antigens often also reflect latent infection explaining the poor performance of antibody-based tests for active TB in TB-endemic settings. Our results suggest that rather a combination of serological responses against selected protein and non-protein antigens and different Ig classes should be investigated for TB serodiagnostics. [ABSTRACT FROM AUTHOR]

Antibodies against mycobacterial proteins are highly specific, but lack sensitivity, whereas cytokines have been shown to be sensitive but not very specific in the diagnosis of tuberculosis (TB). We assessed combinations between antibodies and cytokines for diagnosing TB. Immuoglubulin (Ig) A and IgM antibody titres against selected mycobacterial antigens including Apa, NarL, Rv3019c, PstS1, LAM, "Kit 1" (MTP64 and Tpx)", and "Kit 2" (MPT64, Tpx and 19 kDa) were evaluated by ELISA in plasma samples obtained from individuals under clinical suspicion for TB. Combinations between the antibody titres and previously published cytokine responses in the same participants were assessed for diagnosing active TB. Antibody responses were more promising when used in combination (AUC of 0.80), when all seven antibodies were combined. When anti-"Kit 1"-IgA levels were combined with five host cytokine biomarkers, the AUC increased to 97% (92–100%) with a sensitivity of 95% (95% CI, 73–100%), and specificity of 88.5% (95% CI, 68.7–97%) achieved after leave-one-out cross validation. When used in combination, IgA titres measured with ELISA against multiple Mycobacterium tuberculosis antigens may be useful in the diagnosis of TB. However, diagnostic accuracy may be improved if the antibodies are used in combination with cytokines. • Antibody-based TB tests are known to be highly specific whereas host cytokine responses have been shown to be sensitive. • An approach involving the combination of anti-MTB antibodies and cytokines was assessed as a tool for TB diagnosis. • Antibodies alone were promising but diagnostic accuracy increased when they were used in combination with cytokines. • Combining antibodies with up to five host inflammatory biomarkers may be a useful approach for the diagnosis of TB. [ABSTRACT FROM AUTHOR]

Summary: Treatment failure and relapse may affect many tuberculosis (TB) patients who undergo standard anti-TB therapy. Several independent studies suggested unsuccessful sputum culture conversion at month 2 of treatment (slow response) as risk factor for treatment failure and relapse. However, earlier than month 2 identification of patients with a high risk for poor treatment outcome would offer significant clinical trial and individual patient care benefits. The sensitivity and specificity of serological IgG and IgA responses against four recombinant mycobacterial antigens (ABC transporter PstS3, secreted l-alanine dehydrogenase, culture filtrate protein Tpx and 6 kDa early secretory antigenic target esxa (ESAT-6)) were evaluated separately in a blinded fashion in 21 smear-positive pulmonary TB patient sera taken at diagnosis before commencement of directly observed anti-TB treatment short course comprising 13 slow responder and eight fast responder subjects. We observed a general pattern of higher antibody levels in sera of slow responders. Most pronounced were high levels of anti-alanine dehydrogenase IgG, anti-Tpx IgG, anti-ESAT-6 IgG and anti-ESAT-6 IgA antibodies at diagnosis being associated with slow response with 100% specificity each and 46.2, 53.8, 53.8 or 53.8% sensitivity, respectively, when compared to fast response (P = 0.020, 0.021, 0.040 and 0.011, respectively). Discriminant analysis showed that the combined use of anti-Tpx IgG and anti-ESAT-6 IgA antibody titers before treatment predicted slow responders with 90.5% accuracy. These preliminary results suggest that combinations of serodiagnostic markers measured prior to initiation of treatment may be suitable for the prediction of early treatment response. This approach holds promise and requires further evaluation for its utility in the prediction of treatment failure and relapse, the evaluation of new TB therapeutics, as well as in the care of individual patients. [ABSTRACT FROM AUTHOR]