Multiplexed rapid antigen tests developed using multicolored nanoparticles and cross-reactive antibody pairs: Implications for pandemic preparedness.

Global public health infrastructure is unprepared for emerging pathogen epidemics, in part because diagnostic tests are not developed in advance. The recent Zika, Ebola, and SARS-CoV-2 virus epidemics are cases in point. We demonstrate here that multicolored gold nanoparticles, when coupled to cross-reactive monoclonal antibody pairs generated from a single immunization regimen, can be used to create multiple diagnostics that specifically detect and distinguish related viruses. The multiplex approach for specific detection centers on immunochromatography with pairs of antibody-conjugated red and blue gold nanoparticles, coupled with clustering algorithms to detect and distinguish related pathogens. Cross-reactive antibodies were used to develop rapid tests for i) Dengue virus serotypes 1-4, ii) Zika virus, iii) Ebola and Marburg viruses, and iv) SARS-CoV and SARS-CoV-2 viruses. Multiplexed rapid antigen tests based on multicolored nanoparticles and cross-reactive antibodies and can be developed prospectively at low cost to improve preparedness for epidemic outbreaks.

Monoclonal antibody pairs against SARS-CoV-2 for rapid antigen test development.

BACKGROUND: The focus on laboratory-based diagnosis of coronavirus disease 2019 (COVID-19) warrants alternative public health tools such as rapid antigen tests. While there are a number of commercially available antigen tests to detect severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), all cross-react with the genetically similar SARS-CoV-1 or require an instrument for results interpretation. METHODOLOGY/PRINCIPAL FINDINGS: We developed and validated rapid antigen tests that use pairs of murine-derived monoclonal antibodies (mAbs), along with gold nanoparticles, to detect SARS-CoV-2 with or without cross-reaction to SARS-CoV-1 and other coronaviruses. In this development, we demonstrate a robust antibody screening methodology for the selection of mAb pairs that can recognize SARS-CoV-2 spike (S) and nucleocapsid (N) proteins. Linear epitope mapping of the mAbs helped elucidate SARS-CoV-2 S and N interactions in lateral flow chromatography. A candidate rapid antigen test for SARS-CoV-2 N was validated using nasal swab specimens that were confirmed positive or negative by quantitative reverse-transcription polymerase chain reaction (RT-PCR). Test results were image-captured using a mobile phone and normalized signal pixel intensities were calculated; signal intensities were inversely correlated to RT-PCR cycle threshold (Ct) value. CONCLUSION/SIGNIFICANCE: Overall, our results suggest that the rapid antigen test is optimized to detect SARS-CoV-2 N during the acute phase of COVID-19. The rapid antigen tests developed in this study are alternative tools for wide scale public health surveillance of COVID-19.

Comparative Evaluation of Rapid Isothermal Amplification and Antigen Assays for Screening Testing of SARS-CoV-2.

Human transmission of SARS-CoV-2 and emergent variants of concern continue to occur globally, despite mass vaccination campaigns. Public health strategies to reduce virus spread should therefore rely, in part, on frequent screening with rapid, inexpensive, and sensitive tests. We evaluated two digitally integrated rapid tests and assessed their performance using stored nasal swab specimens collected from individuals with or without COVID-19. An isothermal amplification assay combined with a lateral flow test had a limit of detection of 10 RNA copies per reaction, and a positive percent agreement (PPA)/negative percent agreement (NPA) during the asymptomatic and symptomatic phases of 100%/100% and 95.83/100%, respectively. Comparatively, an antigen-based lateral flow test had a limit of detection of 30,000 copies and a PPA/NPA during the asymptomatic and symptomatic phases of 82.86%/98.68% and 91.67/100%, respectively. Both the isothermal amplification and antigen-based lateral flow tests had optimized detection of SARS-CoV-2 during the peak period of transmission; however, the antigen-based test had reduced sensitivity in clinical samples with qPCR Ct values greater than 29.8. Low-cost, high-throughput screening enabled by isothermal amplification or antigen-based techniques have value for outbreak control.

Pooling of Samples for SARS-CoV-2 Detection Using a Rapid Antigen Test.

While molecular assays, such as reverse-transcription polymerase chain reaction (RT-PCR), have been widely used throughout the coronavirus disease 2019 (COVID-19) pandemic, the technique is costly and resource intensive. As a means to reduce costs and increase diagnostic efficiency, pooled testing using RT-PCR has been implemented. However, pooling samples for antigen testing has not been evaluated. Here, we propose a proof-of-concept pooling strategy for antigen testing that would significantly expand SARS-CoV-2 surveillance, especially for low-to-middle income countries, schools, and workplaces. Our laboratory-based testing demonstrates that combining of up to 20 nasal swab specimens per pool can expand surveillance with antigen tests, even if a pool contains only one positive sample.

Development and Validation of a Rapid Lateral Flow E1/E2-Antigen Test and ELISA in Patients Infected with Emerging Asian Strain of Chikungunya Virus in the Americas.

Since its 2013 emergence in the Americas, Chikungunya virus (CHIKV) has posed a serious threat to public health. Early and accurate diagnosis of the disease, though currently lacking in clinics, is integral to enable timely care and epidemiological response. We developed a dual detection system: a CHIKV antigen E1/E2-based enzyme-linked immunosorbent assay (ELISA) and a lateral flow test using high-affinity anti-CHIKV antibodies. The ELISA was validated with 100 PCR-tested acute Chikungunya fever samples from Honduras. The assay had an overall sensitivity and specificity of 51% and 96.67%, respectively, with accuracy reaching 95.45% sensitivity and 92.03% specificity at a cycle threshold (Ct) cutoff of 22. As the Ct value decreased from 35 to 22, the ELISA sensitivity increased. We then developed and validated two lateral flow tests using independent antibody pairs. The sensitivity and specificity reached 100% for both lateral flow tests using 39 samples from Colombia and Honduras at Ct cutoffs of 20 and 27, respectively. For both lateral flow tests, sensitivity decreased as the Ct increased after 27. Because CHIKV E1/E2 are exposed in the virion surfaces in serum during the acute infection phase, these sensitive and specific assays demonstrate opportunities for early detection of this emerging human pathogen.

Serotype-specific detection of dengue viruses in a nonstructural protein 1-based enzyme-linked immunosorbent assay validated with a multi-national cohort.

BACKGROUND: Dengue virus (DENV) infections pose one of the largest global barriers to human health. The four serotypes (DENV 1-4) present different symptoms and influence immune response to subsequent DENV infections, rendering surveillance, risk assessments, and disease control particularly challenging. Early diagnosis and appropriate clinical management is critical and can be achieved by detecting DENV nonstructural protein 1 (NS1) in serum during the acute phase. However, few NS1-based tests have been developed that are capable of differentiating DENV serotypes and none are currently commercially available. METHODOLOGY/PRINCIPLE FINDINGS: We developed an enzyme-linked immunosorbent assay (ELISA) to distinguish DENV-1-4 NS1 using serotype-specific pairs of monoclonal antibodies. A total of 1,046 antibodies were harvested from DENV-immunized mice and screened for antigen binding affinity. ELISA clinical performance was evaluated using 408 polymerase chain reaction-confirmed dengue samples obtained from patients in Brazil, Honduras, and India. The overall sensitivity of the test for pan-DENV was 79.66% (325/408), and the sensitivities for DENV-1-4 serotyping were 79.1% (38/48), 80.41% (78/97), 100% (45/45), and 79.6% (98/123), respectively. Specificity reached 94.07-100%. SIGNIFICANCE: Our study demonstrates a robust antibody screening strategy that enabled the development of a serotype NS1-based ELISA with maximized specific and sensitive antigen binding. This sensitive and specific assay also utilized the most expansive cohort to date, and of which about half are from Latin America, a geographic region severely underrepresented in previous similar studies. This ELISA test offers potential enhanced diagnostics during the acute phase of infection to help guide patient care and disease control. These results indicate that this ELISA is a promising aid in early DENV-1-4 diagnosis and surveillance in regions of endemicity in addition to offer convenient monitoring for future vaccine interventions.

Electroforesis horizontal en geles de poliacrilamida en la detección y tipificación del virus de papiloma humano / Horizontal electrophoresis in polyacrylamide gels in the detection and typing of human papillomavirus

OBJETIVO: estandarizar el uso de electroforesis horizontal en poliacrilamida como un método rápido de fácil implementación y de alta sensibilidad para la detección y tipificación del virus del papiloma humano por reacción en cadena de la polimerasa-polimorfismos de longitud de fragmentos de restricción con la enzima HpyCH4V como única enzima de restricción. MÉTODOS: Se utilizó el ácido desoxirribonucleico de 17 tipos de virus del papiloma humano, clonados en la colección del Laboratorio de Biología y Medicina Experimental (LABIOMEX-ULA), para la amplificación de la región flanqueada por los oligonucleótidos MY09/ MY11, los amplificados obtenidos se sometieron a digestión enzimática con la enzima HpyCH4V. El producto se corrió en geles de poliacrilamida de rápida polimerización en equipos de electroforesis horizontales. El ácido desoxirribonucleico se tiñó con bromuro de etidio y fueron fotografiados con la utilización de un trans-iluminador de luz ultravioleta. RESULTADOS: Se corrieron muestras de 17 tipos diferentes de virus del papiloma humano en geles de poliacrilamida en electroforesis horizontal sudmarina. Se observaron patrones de digestión, con la enzima de restricción HpyCH4V, bien definidos y distintos para 15 tipos diferentes. Se presentó una coincidencia de patrón polimorfismos de longitud de fragmentos de restricción para los tipos 45 y 52 ambos de alto riesgo. Se obtuvo una excelente resolución en corridas de 2,5 cm de longitud para cualquier patrón polimorfismos de longitud de fragmentos de restricción de los 17 tipos de virus del papiloma humano analizados. CONCLUSIÓN: El análisis de las corridas permitió una eficiente caracterización de los 17 tipos virales. La comparación del índice de movilidad relativa con polimorfismos de longitud de fragmentos de restricción virtual de los fragmentos amplificados presentó diferencias mínimas, el análisis de la movilidad en agarosa y poliacrilamida se ajustaron perfectamente permitiendo la sustitución de la agarosa por la poliacrilamida.

OBJECTIVE: to standardize the use of horizontal electrophoresis in polyacrylamide as a quick method of easy implementation and high sensitivity for the detection and typing of Human Papillomavirus by PCR-FRLP with HpyCH4V enzyme as unique restriction enzyme. METHODS: DNA from 17 Human Papillomavirus types, cloned in the collection of the Laboratory of Experimental Biology and Medicine, for amplification of the region flanked by the MY09/ MY11 oligonucleotides were used, the amplified obtained were subjected to enzymatic digestion with the enzyme HpyCH4V. The product was run on polyacrylamide gels rapid polymerization horizontal electrophoresis equipment. Stained with ethidium bromide and were photographed with the use of a trans-illuminating UV. RESULTS: Samples of 17 different Human Papillomavirus types polyacrylamide gel electrophoresis were run horizontally. Digestion patterns were observed with the restriction enzyme HpyCH4V, well-defined and different for different types 15. A pattern match for RFLP types 45 and 52 both high risk presented. Excellent resolution on runs of 2.5 cm in length for any RFLP pattern of the 17 Human Papillomavirus types analyzed was obtained. CONCLUSION: The analysis of the runs allows efficient characterization of the 17 Human Papillomavirus types. Comparing the relative mobility rate with the virtual RFLP of amplified fragments present minimal differences, analyzing mobility in agarose and polyacrylamide perfectly adjusted allowing for substitution of agarose by polyacrylamide.