Serum Cell-Free DNA-based Detection of Mycobacterium avium Complex Infection.

Rationale: Mycobacterium avium complex (MAC) is the most common cause of nontuberculous mycobacterial (NTM) pulmonary disease (PD), which exhibits increasing global incidence. Current microbiologic methods routinely used in clinical practice lack sensitivity and have long latencies, leading to delays in diagnosis and treatment initiation and evaluation. A clustered regularly interspaced short palindromic repeats (CRISPR)-based assay that measures MAC cell-free DNA (cfDNA) concentrations in serum could provide a rapid means to detect MAC infection and monitor response to antimicrobial treatment. Objectives: To develop and optimize a CRISPR MAC assay for MAC infection detection and to evaluate its diagnostic and prognostic performance in two MAC disease cohorts. Methods: MAC cfDNA serum concentrations were measured in individuals with diagnoses of MAC disease or who had bronchiectasis or chronic obstructive pulmonary disease diagnoses without histories of NTM PD or NTM-positive sputum cultures. Diagnostic performance was analyzed using pretreatment serum from two cohorts. Serum MAC cfDNA changes during MAC PD treatment were evaluated in a subset of patients with MAC PD who received macrolide-based multidrug regimens. Measurements and Main Results: The CRISPR MAC assay detected MAC cfDNA in MAC PD with 97.6% (91.6-99.7%) sensitivity and 97.6% (91.5-99.7%) specificity overall. Serum MAC cfDNA concentrations markedly decreased after MAC-directed treatment initiation in patients with MAC PD who demonstrated MAC culture conversion. Conclusions: This study provides preliminary evidence for the utility of a serum-based CRISPR MAC assay to rapidly detect MAC infection and monitor the response to treatment.

Development of a CRISPR-Cas12a rapid diagnostic for human cytomegalovirus.

Despite decades of research, human cytomegalovirus (CMV) continues to contribute to significant morbidity and mortality in transplant settings and remains the leading cause of viral congenital infections. Clinical diagnosis of CMV infection and/or reactivation under these settings is completed using real time quantitative polymerase chain reaction (RT-qPCR). This assay performs well but is hampered by poor sensitivity and a lack of standardization among testing facilities. A point-of-care rapid diagnostic to determine CMV viremia could address these issues and improve patient care. In this manuscript, we introduce clustered regularly interspaced short palindromic repeats (CRISPR)-Cas12a technology to design and validate a rapid diagnostic for CMV. This system was tested using CMV spiked human saliva and urine samples. Sensitivity of the assay was ∼10 infectious units (IU)/mL. Specificity of the assay was robust and failed to detect other herpesviruses. Collectively, we have designed and validated a rapid diagnostic for CMV that overcomes limitations of the current standard diagnostic. This assay has the potential to be used as a point-of-care screening tool in transplant and neonatal settings.

CRISPR detection of circulating cell-free Mycobacterium tuberculosis DNA in adults and children, including children with HIV: a molecular diagnostics study.

BACKGROUND: Tuberculosis remains a leading cause of global mortality, especially for adults and children living with HIV (CLHIV) underdiagnosed by sputum-based assays. Non-sputum-based assays are needed to improve tuberculosis diagnosis and tuberculosis treatment monitoring. Our aim in this study was to determine whether ultrasensitive detection of Mycobacterium tuberculosis cell-free DNA (Mtb-cfDNA) in blood can diagnose tuberculosis and evaluate tuberculosis treatment responses. METHODS: In this molecular diagnostics study we analysed archived serum from two patient populations evaluated for tuberculosis in Eswatini and Kenya to detect Mtb-cfDNA, analysing serum from all individuals who had both sufficient serum volumes and clear diagnostic results. An optimised CRISPR-mediated tuberculosis (CRISPR-TB) assay was used to detect Mtb-cfDNA in serum at enrolment from adults and children with presumptive tuberculosis and their asymptomatic household contacts, and at enrolment and during tuberculosis treatment from a cohort of symptomatic CLHIV at high risk for tuberculosis, who provided longitudinal serum at enrolment and during tuberculosis treatment. FINDINGS: CRISPR-TB identified microbiologically and clinically confirmed tuberculosis cases in the predominantly HIV-negative Eswatini adult cohort with 96% sensitivity (27 [96%] of 28, 95% CI 80-100) and 94% specificity (16 [94%] of 17, 71-100), and with 83% sensitivity (5 [83%] of 6, 36-100) and 95% specificity (21 [95%] of 22, 77-100) in the paediatric cohort, including all six cases of extrapulmonary tuberculosis. In the Kenyan CLHIV cohort, CRISPR-TB detected all (13 [100%] of 13, 75-100) confirmed tuberculosis cases and 85% (39 [85%] of 46, 71-94) of unconfirmed tuberculosis cases diagnosed by non-microbiological clinical findings. CLHIV who were CRISPR-TB positive at enrolment had a 2·4-times higher risk of mortality by 6 months after enrolment. Mtb-cfDNA signal decreased after tuberculosis treatment initiation, with near or complete Mtb-cfDNA clearance by 6 months after tuberculosis treatment initiation. INTERPRETATION: CRISPR-mediated detection of circulating Mtb-cfDNA shows promise to increase the identification of paediatric tuberculosis and HIV-associated tuberculosis, and potential for early diagnosis and rapid monitoring of tuberculosis treatment responses. FUNDING: US Department of Defense, National Institute of Child Health and Human Development, National Institute of Allergy and Infectious Diseases, University of Washington Center for AIDS Research, and the Weatherhead Presidential Endowment fund.

CRISPR-based assay reveals SARS-CoV-2 RNA dynamic changes and redistribution patterns in non-human primate model.

Mounting evidence indicates that SARS-CoV-2 can infect multiple systemic tissues, but few studies have evaluated SARS-CoV-2 RNA dynamics in multiple specimen types due to their reduced accessibility and diminished performance of RT-qPCR with non-respiratory specimens. Here, we employed an ultrasensitive CRISPR-RT-PCR assay to analyze longitudinal mucosal (nasal, buccal, pharyngeal, and rectal), plasma, and breath samples from SARS-CoV-2-infected non-human primates (NHPs) to detect dynamic changes in SARS-CoV-2 RNA level and distribution among these specimens. We observed that CRISPR-RT-PCR results consistently detected SARS-CoV-2 RNA in all sample types at most time points post-infection, and that SARS-CoV-2 infection dose and administration route did not markedly affect the CRISPR-RT-PCR signal detected in most specimen types. However, consistent RT-qPCR positive results were restricted to nasal, pharyngeal, and rectal swab samples, and tended to decrease earlier than CRISPR-RT-PCR results, reflecting lower assay sensitivity. SARS-CoV-2 RNA was detectable in both pulmonary and extrapulmonary specimens from early to late infection by CRISPR-RT-PCR, albeit with different abundance and kinetics, with SARS-CoV-2 RNA increases detected in plasma and rectal samples trailing those detected in upper respiratory tract samples. CRISPR-RT-PCR assays for SARS-CoV-2 RNA in non-respiratory specimens may thus permit direct diagnosis of suspected COVID-19 cases missed by RT-PCR, while tracking SARS-CoV-2 RNA in minimally invasive alternate specimens may better evaluate the progression and resolution of SARS-CoV-2 infections.

Rapid detection of multiple SARS-CoV-2 variants of concern by PAM-targeting mutations.

SARS-CoV-2 variants of concern (VOCs) that increase transmission or disease severity or reduce diagnostic or vaccine efficacy continue to emerge across the world. Current methods available to rapidly detect these can be resource intensive and thus sub-optimal for large-scale deployment needed during a pandemic response. Here, we describe a CRISPR-based assay that detects mutations in spike gene CRISPR PAM motif or seed regions to identify a pan-specific VOC single-nucleotide polymorphism (SNP)) ((D614G) and Alpha- and Delta-specific (S982A and D950N) SNPs. This assay exhibits good diagnostic sensitivity and strain specificity with nasal swabs and is designed for use in laboratory and point-of-care settings. This should enable rapid, high-throughput VOC identification required for surveillance and characterization efforts to inform clinical and public health decisions. Furthermore, the assay can be adapted to target similar SNPs associated with emerging SARS-CoV-2 VOCs, or other rapidly evolving viruses.

Liposome-mediated detection of SARS-CoV-2 RNA-positive extracellular vesicles in plasma.

Plasma SARS-CoV-2 RNA may represent a viable diagnostic alternative to respiratory RNA levels, which rapidly decline after infection. Quantitative PCR with reverse transcription (RT-qPCR) reference assays exhibit poor performance with plasma, probably reflecting the dilution and degradation of viral RNA released into the circulation, but these issues could be addressed by analysing viral RNA packaged into extracellular vesicles. Here we describe an assay approach in which extracellular vesicles directly captured from plasma are fused with reagent-loaded liposomes to sensitively amplify and detect a SARS-CoV-2 gene target. This approach accurately identified patients with COVID-19, including challenging cases missed by RT-qPCR. SARS-CoV-2-positive extracellular vesicles were detected at day 1 post-infection, and plateaued from day 6 to the day 28 endpoint in a non-human primate model, while signal durations for 20-60 days were observed in young children. This nanotechnology approach uses a non-infectious sample and extends virus detection windows, offering a tool to support COVID-19 diagnosis in patients without SARS-CoV-2 RNA detectable in the respiratory tract.

Sensitive tracking of circulating viral RNA through all stages of SARS-CoV-2 infection.

BACKGROUNDCirculating severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA may represent a more reliable indicator of infection than nasal RNA, but quantitative reverse transcription PCR (RT-qPCR) lacks diagnostic sensitivity for blood samples.METHODSA CRISPR-augmented RT-PCR assay that sensitively detects SARS-CoV-2 RNA was employed to analyze viral RNA kinetics in longitudinal plasma samples from nonhuman primates (NHPs) after virus exposure; to evaluate the utility of blood SARS-CoV-2 RNA detection for coronavirus disease 2019 (COVID-19) diagnosis in adults cases confirmed by nasal/nasopharyngeal swab RT-PCR results; and to identify suspected COVID-19 cases in pediatric and at-risk adult populations with negative nasal swab RT-qPCR results. All blood samples were analyzed by RT-qPCR to allow direct comparisons.RESULTSCRISPR-augmented RT-PCR consistently detected SARS-CoV-2 RNA in the plasma of experimentally infected NHPs from 1 to 28 days after infection, and these increases preceded and correlated with rectal swab viral RNA increases. In a patient cohort (n = 159), this blood-based assay demonstrated 91.2% diagnostic sensitivity and 99.2% diagnostic specificity versus a comparator RT-qPCR nasal/nasopharyngeal test, whereas RT-qPCR exhibited 44.1% diagnostic sensitivity and 100% specificity for the same blood samples. This CRISPR-augmented RT-PCR assay also accurately identified patients with COVID-19 using one or more negative nasal swab RT-qPCR results.CONCLUSIONResults of this study indicate that sensitive detection of SARS-CoV-2 RNA in blood by CRISPR-augmented RT-PCR permits accurate COVID-19 diagnosis, and can detect COVID-19 cases with transient or negative nasal swab RT-qPCR results, suggesting that this approach could improve COVID-19 diagnosis and the evaluation of SARS-CoV-2 infection clearance, and predict the severity of infection.TRIAL REGISTRATIONClinicalTrials.gov. NCT04358211.FUNDINGDepartment of Defense, National Institute of Allergy and Infectious Diseases, National Institute of Child Health and Human Development, and the National Center for Research Resources.