Practical use of tobravirus-based vector to produce SARS-CoV-2 antigens in plants.

A plant-based heterologous expression system is an attractive option for recombinant protein production because it is based on a eukaryotic system of high feasibility, and low biological risks. Frequently, binary vector systems are used for transient gene-expression in plants. However, plant virus vector-based systems offer advantages for higher protein yields due to their self-replicating machinery. In the present study, we show an efficient protocol using a plant virus vector based on a tobravirus, pepper ringspot virus, that was employed for transient expression of severe acute respiratory syndrome coronavirus 2 partial gene fragments of the spike (named S1-N) and the nucleocapsid (named N) proteins in Nicotiana benthamiana plants. Purified proteins yield of 40-60 µg/g of fresh leaves were obtained. Both proteins, S1-N and N, showed high and specific reactivities against convalescent patients' sera by the enzyme-linked immunosorbent assay format. The advantages and critical points in using this plant virus vector are discussed.

Effectiveness of telemedicine in response to the COVID-19 pandemic.

OBJECTIVE: The aim of this study was to evaluate the utility of the telemedicine care model implemented to treat and guide patients with COVID-19 related symptoms and indicators during the pandemic. METHODS: This is a retrospective study with data collected from the electronic records of standardized forms for assistance. As a way of evaluating the work performed, the number of consultations, types of referrals, efficiency of care, and patient satisfaction were observed. RESULTS: Between April 2 and October 15, 2020, 92 professionals attended 3,660 patients by telemedicine; out of them, 523 (14.3%) were referred to a COVID-19 attending room, 128 (3.5%) to other specialties, 123 (3.4%) to a general emergency department, and 2,886 (78.9%) were monitored via home care. Of the total number of patients, 81 (2.2%) were hospitalized, and 13 (0.35%) died. CONCLUSION: Telemedicine offered useful tools for the care, treatment, and monitoring of patients with COVID-19 during the pandemic. The service was considered by most respondents as satisfactory, resolutive, or safe.

A molecular test based on RT-LAMP for rapid, sensitive and inexpensive colorimetric detection of SARS-CoV-2 in clinical samples (preprint)

Until there is an effective implementation of COVID-19 vaccination program, a robust testing strategy, along with prevention measures, will continue to be the most viable way to control disease spread. Such a strategy should rely on disparate diagnostic tests to prevent a slowdown in testing due to lack of materials and reagents imposed by supply chain problems, which happened at the beginning of the pandemic. In this study, we have established a single-tube test based on RT-LAMP that enables the visual detection of less than 100 viral genome copies of SARS-CoV-2 within 30 minutes. We benchmarked the assay against the gold standard test for COVID-19 diagnosis, qRT-PCR, using 177 nasopharyngeal RNA samples. For Ct ≤ 32, the RT-LAMP assay had a sensitivity of 100% and a specificity of 96.1%. Additionally, we set up a RNA extraction-free RT-LAMP test capable of detecting SARS-CoV-2 directly from saliva samples, albeit with lower sensitivity. The saliva was self-collected and the collection tube remained closed until inactivation, thereby ensuring the protection of the testing personnel. As expected, RNA extraction from saliva samples increased the sensitivity of the test. To lower the costs associated with RNA extraction, we performed this step using an alternative protocol that uses plasmid DNA extraction columns. We also produced the enzymes needed for the assay and established an in-house-made RT-LAMP test independent of specific distribution channels. Finally, we developed a new colorimetric method that allowed the detection of LAMP products by the visualization of an evident color shift, regardless of the reaction pH.