Highlights The new antigen tests for COVID19 are an indispensable tool in the control of the pandemic due to their adequate sensitivity and specificity. The implementation of the point of care technique in primary care is feasible and has good results. Less than 5 days of evolution of the onset of symptoms and CT less than 27 in the PCR would define the results of the antigen techniques.

Background: Real-time reverse transcription polymerase chain reaction (RT-qPCR) is the current recommended laboratory method to diagnose SARS-CoV-2 acute infection, several factors such as requirement of special equipment, time consuming, high cost and skilled staff limit the use of these time-consuming molecular techniques. A more rapid and high-throughput method is in growing demand Methods: Evaluate the performances of the Panbio COVID-19 AG Rapid Test Device (Nasopharyngeal), a rapid immunochromatographic test for the detection of SARS-CoV-2 antigen, in comparison to RT-qPCR. Results: The RDT evaluated in this study showed a high sensitivity and specificity in samples mainly obtained during the first week of symptoms and with high viral loads. Conclusions: This assay seems to be an effective strategy for controlling the COVID-19 pandemic for the rapid identification and isolation of SARS-CoV-2 infected patients.

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Objectives Antigen rapid diagnostic tests (Ag-RDT) have been developed as reliable tools to control the SARS-CoV-2 pandemic. The objective of our study was to evaluate the diagnostic performance of two Ag-RDTs. Methods We evaluated CerTest SARS-CoV-2 Ag One Step Card Test and Panbio COVID-19 Ag Rapid Test Device Ag-RDTs. We included 320 nasopharyngeal samples: 150 PCR negative samples to assess the specificity and 170 PCR positive samples to evaluate the sensitivity. We also evaluated their sensitivity according to cycle threshold (Ct) values and the time from the onset of symptoms. Tests were compared using the McNemar’s test and agreement was evaluated using the kappa score ( k ). Results Both Ag-RDTs showed a specificity of 100%. Overall sensitivity was 53.5% for CerTest and 60.0% for Panbio . For samples with 25, sensitivity was 94.0% for CerTest and 96.4% for Panbio (p = 0.500). Regarding samples with Ct>25, sensitivity was 14.0% for CerTest and 24.4% for Panbio (p = 0.004). Sensitivity for samples within the first 5 days after the onset of symptoms were 84.8% for CerTest and 91.3% for Panbio (p = 0.250) and notably decreased for samples taken after the fifth day. Both Ag-RDTs showed an excellent agreement between them (agreement = 96.7%, k = 0.920). Agreement with PCR was also excellent for high viral load samples (Ct<25) for CerTest (98.0%, k = 0.954) and Panbio (98.8%, k = 0.973). Conclusions CerTest SARS-CoV-2 and Panbio COVID-19 Ag showed excellent performance and agreement results for samples with high viral loads (Ct 25) or samples taken within the first 5 days after the onset of symptoms.

Transgenic plants expressing recombinant immunoglobulins have arisen as an alternative technology for the large-scale production of antibodies useful in therapeutics and in industrial processes. In the present paper we report the expression in transgenic tobacco ( Nicotiana tabacum ) of an anti-HBsAg [anti-(hepatitis B virus surface antigen)] mouse IgG1 mAb (monoclonal antibody), currently used for the industrial purification of the recombinant vaccine antigen. Using the sweet potato sporamin signal peptide, a KDEL (Lys-Asp-Glu-Leu) ER (endoplasmic reticulum) anchorage domain, and a heavy- and light-chain gene tandem construction, we generated F1 plants in which the expression of the antibody accounted for 0.5% of the total soluble proteins. The 'plantibody' (functional IgG antibody produced in plants) was easily purified by Protein A-Sepharose chromatography with a yield of approximately 35 microg/g of fresh leaf material, and its glycosylation indicated that, irrespective of the KDEL signal, the molecule is modified in both the ER and Golgi. Finally, a successful comparison of the plantibody with the ascites-derived mAb in the immunoaffinity purification of the vaccine recombinant HBsAg was performed. Taken as a whole, our results show that the large-scale production of this antibody of industrial relevance in transgenic tobacco is feasible.