Early detection of SARS-CoV-2 using molecular techniques is paramount to the fight against COVID-19. Due to its high sensitivity and specificity, RT-qPCR is the 'gold standard' method for this purpose. However, its technical requirements, processing time and elevated costs hamper its use towards massive and timely molecular testing for COVID-19 in rural and socioeconomically deprived areas of Latin America. The advent and rapid evolution of CRISPR-Cas technology has boosted the development of new pathogen detection methodologies. Recently, DETECTR-a combination of isothermal RT-LAMP amplification and Cas12a-mediated enzymatic detection- has been successfully validated in the Netherlands and the USA as a rapid and low-cost alternative to RT-qPCR for the detection of SARS-CoV-2 from nasopharyngeal swabs. Here, we evaluated the performance of RCSMS, a locally adapted variant of DETECTR, to ascertain the presence of SARS-CoV-2 in saliva samples from 276 patients in two hospitals in Lima, Peru (current status over a total of 350 samples). We show that a low-cost thermochemical treatment with TCEP/EDTA is sufficient to inactivate viral particles and cellular nucleases in saliva, eliminating the need to extract viral RNA with commercial kits, as well as the cumbersome nasopharyngeal swab procedure and the requirement of biosafety level 2 laboratories for molecular analyses. Our clinical validation shows that RCSMS detects up to 5 viral copies per reaction in 40 min, with sensitivity and specificity of 93.8% and 99.0% in the field, respectively, relative to RT-qPCR. Since CRISPR-Cas biosensors can be easily reprogrammed by using different guide RNA molecules, RCSMS has the potential to be quickly adapted for the detection of new SARS-CoV-2 variants. Notably, estimation of its negative and positive predictive values suggests that RCSMS can be confidently deployed in both high and low prevalence settings. Furthermore, our field study validates the use of lateral flow strips to easily visualize the presence of SARS-CoV-2, which paves the way to deploy RCSMS as a 'point of care' test in environments with limited access to state-of-the-art diagnostic laboratories. In sum, RCSMS is a fast, efficient and inexpensive alternative to RT-qPCR for expanding COVID-19 testing capacity in low- and middle-income countries.

SUMMARYThe larvae-to-adult development on the life cycle of zoonotic parasitic tapewormTaenia soliuminvolves striking -but clinically unappreciated-events with pivotal importance in cestode biology. Unlike the ones related to the intermediate host, the early-adult stages can be addressedin vitrooffering a useful model to study evagination, strobilation and worm development. In the absence of a stage-specific transcriptome, postgenomic data exploration followed by single-gene relative expression analysis by RT-qPCR (reverse transcription-quantitative PCR) are useful strategies to gather information on the regulation of genes of interest during parasite development. However, this approach requires the validation of an endogenous reference gene (RG) to achieve accurate comparisons.Therefore, we analyzed the expression stability of 17 candidate RGs on the context of the early-adult stages ofT. soliumclassified as non-evaginated and evaginated larvae (cysts). The comprehensive tool RefFinder ranked malate dehydrogenase as the most stable gene within these conditions, and its suitability for relative quantification was validated by normalizing the expression of the transporter TGTP1 gene, known for being upregulated upon evagination. This study is the first attempt in finding reliable normalization standards for transcript exploration in genus Taenia.