A Specific miRNA Encoded by SARS-CoV-2 as a Diagnostic Tool to Predict Disease Severity in COVID-19 Patients

Coronavirus disease is caused by SARS-CoV-2, known as 2019 novel coronavirus (2019-nCoV). To date has caused a large number of deaths causing serious respiratory illness such as pneumonia and lung failure, therefore representing a serious threat to public health. The etiological agent belongs to the subfamily Orthocoronavirinae in the family Coronaviridae, Order Nidovirales. The genome of coronaviruses is composed of an enveloped, positive-sense, single-stranded RNA with a size varying between 26 kb and 32 kb, becoming the largest genome of known RNA viruses so far. Similar to RNA viruses, this family is characterized by genetic variability and high recombination rate that enable them to be easily distributed among humans and animals worldwide. Considering the huge impact of the pandemic, it is urgent to gain understanding and to build strategies to contain the viral spread. To date, different diagnostic kits for testing the illness are available. Besides diagnosis, the prediction of the severity and prognosis of COVID-19 is essential to stratify patients and allocate them in the adequate medical facilities so as to reduce mortality rates. It has been reported that microRNAs (miRNAs) are valuable biomarkers for disease diagnosis, prognosis and classification. MiRNAs are defined as a class of non-coding RNAs that are able to regulate gene expression by specific binding to complementary regions in coding messenger RNAs, leading to translational repression or decay. Not only that, but also they can be important modulators of viral infections.Previous studies have revealed the presence of miRNA-like small RNAs (milRNAs), which can be encoded by RNA viruses and can actively disrupt the host innate immune responses in order to create a favourable environment for viral replication. On the other side, cellular miRNAs can also play a role on virus replication and pathogenesis.In this case, this pilot project is aimed at their valuable diagnostic potential, in order to diagnose and stratify patients under viral infection. The project came up after receiving information from a Chinese research group, requesting their results to be replicated in Caucasian population. The ROC curves were constructed to demonstrate the accuracy of this specific miRNA in COVID-19 patient stratification and discerning between severe patients from healthy controls. Both ROC curves suggested the miRNA as precise biomarker for differential diagnosis and prognosis of disease severity.