MicroRNA biomarkers and identification of infectious agents
MicroRNA biomarkers and identification of infectious agents
Reza Yari,1,*
1. Department of Biology, Borujerd Branch, Islamic Azad University, Borujerd, Iran.
Introduction: Non-coding microRNAs are 18-22 nucleotides and evolutionarily conserved. They control gene expression after transcription by degrading mRNA or inhibiting it’s translation. They are involved in control of physiological and pathological processes and act as oncogenes or tumor suppressors. About 2,600 miRNAs have been identified in the human genome, of which 2,000 types are found in biofluids. The amount of miRNA in plasma is 9000-134000 copies/μl. They are used as diagnostic biomarkers in a wide range of non-infectious diseases such as cancers, autoimmune diseases, Alzheimer's, etc., but their use in infectious diseases is relatively weak, while infectious diseases contribute to 15% of deaths and due to the rapid and simple spread of the factors epidemic infections such as Covid-19 require a quick, accurate, specific and early identification so that health and treatment interventions can be carried out as soon as possible.
Methods: Traditional methods for identifying pathogens include in vitro culture, isolation, protein-based evaluations such as ELISA and serology, microscopic evaluations (histology, pathology, morphology), mass spectrometry, immunofluorescence, nucleic acid-based evaluations such as qPCR, sequencing, Nested RT-PCR, etc, but microRNAs can be identified with lateral flow test device, electrochemical biosensor, μPAD, colorimetric, Microarray, Northern blot, etc.
Results: Many of these methods require large amounts of sample size, high time and cost, high technician expertise and technical limitations, and are sometimes associated with false positive and negative results. Due to their small size, they are stable in biofluids, multiple freeze-thaw cycles and pH changes. Some pathogens such as Rabies and CMV have played a role in escaping and changing the immune system and are difficult to detect in early stages with conventional methods. This leads to low sensitivity and specificity because in many cases the infectious agent is located in a specific area or a special cell, but the advantages of miRNA markers include identifying the infectious agent or infection in the early stages of disease, accurate and sensitive identification of the pathogen, predicting host responses, better guiding treatment choices, diagnosis hidden infections as well as personal medicine with little cost and time.
Conclusion: In order to identify many infectious diseases, the current diagnostic methods are incomplete and insufficient. Many rely on the appearance of symptoms or the presence of pathogen-specific antibodies to detectable titers, but microRNA markers have a high potential to detect infectious agents separately or in the form of expression profiles. They are changed in biofluids due to infections such as bacterial, fungal, parasitic, viral and even prion and they can be used in diagnosis, prognosis and even checking the treatment process. Their application is not without challenges, such as increased expression of miR-146a, which occurs in patients with HBV, HCV, schistosoma, malaria, JEV, HeV, prions and heart disease and therefore it is not a specific microRNA and is related to the activation of the NF-κB signal transduction pathway but their use can be standardized with analytical and validation methods. When infected with Hendra virus, HIV, Tuberculosis, Malaria and Ebola, changes in the miRNA profile of a person can be seen in the early stages of the disease, which indicates the importance of examining changes in the ratios of miRNAs compared to examining them individually.