CROI 2019 Abstract eBook

Abstract eBook

Poster Abstracts

study design. Despite the lower performance compared to sputum-testing methods, OSA provides a promising means of TB detection for populations that are unable to produce adequate sputum including those who are HIV-infected. 718 WITHDRAWN QUANTIFICATION OF CIRCULATING ANTIGENS ENABLES A RAPID BLOOD TB TEST Tony Hu , Penn State University, Hershey, PA, USA Background: Most TB cases are diagnosed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 rapid blood-based diagnostic method independent of mycobacterial isolation to quantify the lowmolecular- weight Mycobacterium tuberculosis (Mtb) antigens (CFP-10 and ESAT-6). Our strategy combines energy mediating porous silicon nanodisks, functionalized with customized antibodies highly specific to Mtb antigen peptides, and high-throughput mass spectrometry (NanoDisk-MS) for dual enhancement of sensitivity and specificity. Methods: Serum samples are subjected to microwave-assisted tryptic digestion and mixed with functionalized NanoDisks and stable isotope-labeled internal standard peptides. The antibody-conjugated nanodisks performs the recognition and enrichment of target peptides and stable isotope-labeled internal standard peptides, following with a Matrix Assisted Laser Deposition Ionization Time-of-Flight Mass Spectrometry (MALDI-TOF MS) analysis. A NanoDisk effect to enhance MALDI-TOF MS signal allows quantification of target peptide at low concentrations, determined by MS intensity ratio of target and isotope-labeled internal standard peptides. Results: We evaluated our platformwith 385 adult and 720 pediatric patients and controls chosen from five highly relevant cohorts (active TB, HIV/TB co- infection, pediatric TB, latent TB, and non-TB mycobacterial infection), provided by multiple institutes worldwide. Sensitivities and specificities of adults (92.1% / 98.2%) and children (89.0% / 97.5%) were achieved in active TB identification. Absolute quantification of circulating antigens was informative in detecting treatment response four days after anti-mycobacterial initiation. Conclusion: 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. Based on our preliminary studies, we are confident that this diagnostic systemwill benefit the global tuberculosis control effort by improving the personalized management of TB.

Poster Abstracts

717 ORAL SWAB ANALYSIS (TB-OSA) FOR NON–SPUTUM-BASED TB DIAGNOSIS IN KENYA Sylvia LaCourse 1 , Rachel Wood 1 , Evans Seko 2 , Gregory S. Ouma 2 , Barbra A. Richardson 1 , Grace John-Stewart 1 , Gerard Cangelosi 1 1 University of Washington, Seattle, WA, USA, 2 Kenya Medical Research Institute, Kisumu, Kenya Background: Despite recent advances in rapid TB diagnostics, sample collection remains challenging in those unable to produce sputum. In published proof-of-concept data, oral swab analysis (OSA) detected M. tuberculosis in 90% of HIV-negative Xpert+ adult TB cases in South Africa, with 100% specificity in negative controls. A larger, follow-on evaluation in the same South African population found 92% sensitivity and 92% specificity relative to sputum Xpert. We evaluated OSA performance in HIV-infected and HIV-uninfected TB suspects in Kenya. Methods: One hundred Kenyan TB suspects (cough >2 weeks, plus >1 additional symptom of fever, night sweats, or weight loss) >13 years of age had oral swabs then sputum for Xpert and culture collected at enrollment and consecutive morning visit. Cryopreserved swabs underwent Mtb DNA extraction and qPCR analysis targeting IS6110 insertion sequence. A predetermined threshold Cq <38 was considered positive (lower Cq indicating a stronger more positive signal). OSA performance was assessed compared to a reference of Xpert or culture. OSA mean Cq values were compared using t-tests. Results: Of 94 participants enrolled with oral swab results, median age was 38 years (IQR 29-44), 48.9%were female, 54.3%were HIV-infected, and 20.1% with history of TB. Among 51 HIV+, 86.3%were on ART and 9.5% had ever received isoniazid preventive therapy (IPT). Nineteen TB cases were identified (18 Xpert/culture+, 1 culture+ only). OSA sensitivity was 68.4% (13/19) with 82.7% (62/75) specificity overall, and 83.3% (5/6) sensitivity and 75.6% (34/45) specificity among HIV-infected. Performance improved on subsequent morning visit samples compared to Xpert alone (sensitivity 80.0% [12/15], specificity 92.3% [60/65]. Mean OSA Cq was stronger (indicated by lower Cq) among Xpert+ vs. Xpert- participants (35.1 +0.8 vs. 37.9 +1.0 SD, p=0.05) and at subsequent morning vs. enrollment visit among OSA+/TB+ (32.5 +2.4 vs. 34.9 +2.6 SD, p=0.008). Conclusion: In this analysis, performance appeared reduced compared to previous analyses, possibly due to differences in setting, population, and/or

719LB BD MAX™ MDR-TB ASSAY FOR DETECTION OF TUBERCULOSIS AND DRUG RESISTANCE Maunank Shah 1 , Josh Betz 1 , Sonia Paradis 2 , Natalie Beylis 3 , Mark Nicol 3 , Lydia Nakiyingi 4 , Moses L. Joloba 4 , Renu Bharadwaj 5 , Neeta N. Pradhan 5 , Vidya Mave 5 ,

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