DATE: April 30, 2019
TIME: 8:00am PDT

Most TB cases are diagnosed by slow and somewhat non-specific microbiological methods. PCR-based GeneXpert MTB/RIF, introduced to improve speed and specificity, has poor sensitivity at low bacterial loads, cannot distinguish live and nonviable bacilli, and has reduced performance in HIV and TB co-infected patients.Serum-based detection of Mtb virulence factors offers direct evidence of TB, but current methods lack adequate sensitivity and specificity. We have developed a blood-based assay for rapid, specific, and high-sensitivity TB diagnosis, which uses nanodisks to enrich Mtb-selective peptides from serum samples. Our approach incorporates several technical advances, including identification of strongly Mtb-selective antigen peptides, and development of antibody-conjugated nanodisks that markedly increase target peptide enrichment and laser desorption/ionization of nanodisk-bound peptides to enhance their detection. This approach disrupts protein complexes, releasing Mtb antigen likely missed by conventional immunoassays targeting intact Mtb proteins. Our method permits rapid multiplex quantification of serum markers specific for robust diagnosis of active TB cases and uses accepted clinical instrumentation to enhance its potential for clinical translation.

Our NanoDisk-enabled TB detection assay addresses sensitivity and speed shortcomings associated with active TB diagnosis, and meets several criteria for a WHO-mandated noninvasive TB assay. Specifically, it (i) uses a small, noninvasive specimen; (ii) does not require bacterial isolation; (iii) has high sensitivity and specificity for active TB cases in extrapulmonary, culture-negative, and HIV-infected TB patients, where diagnosis often requires multiple tests, including invasive procedures. It also (iv) directly quantifies Mtb antigens for rapid monitoring of anti-TB therapy effects; (v) uses a streamlined process amenable to high-throughput operation in clinical and research settings; and (vi) can be performed using equipment already approved by the Food and Drug Administration for other diagnostic assays. However, further improvements in operator time, assay cost, and instrument portability are necessary to meet all WHO guidelines for an optimal noninvasive TB assay.

To further expend the capability of the assay in serving the patients in resource-limited area, we have also developed the solid-state nanopore technology, which can recognize single detection events to quantify two Mtb-specific peptide biomarkers derived from blood samples, to develop a point-of-care diagnostic system. Based on our preliminary studies, we are confident that this diagnostic system will benefit the global tuberculosis control effort by improving the personalized management of TB.