Tsugunori Notomi

Novel Molecular Diagnostic Platform for Tropical Infectious Diseases

Infectious disease is one of the most concerning health issues worldwide. To provide patients with effective medical treatment and prevent the spread of diseases and emergence of drug-resistant strains, quick and reliable diagnostic techniques are in high demand. However, lack of accessibility to such diagnostic systems has resulted in the deterioration of the situation in most developing countries, especially in sub-Saharan tropical countries (Rodrigues et al., 2010). Diagnostics using molecular technologies have emerged as a promising methodology because of their remarkable high sensitivity, and therefore, they have been applied as diagnostic tools for detecting various kinds of pathogens in clinical settings in developed countries. However, resources essential for molecular assays, such as bio-safety cabinets, a stable supply of electricity, and well-experienced technicians, are scarce in most of the peripheral laboratories in developing countries. In this chapter, we would like to describe a recently developed novel diagnostic platform and discuss its application for realizing molecular diagnostics for infectious diseases within resourcelimited settings. Molecular diagnostics comprise the following 3 steps: sample preparation, amplification, and detection. To develop a molecular diagnostic platform with the desired simplicity and performance, it is necessary to introduce element technologies for all the 3 steps, which are less complicated and can be used in peripheral laboratories with limited resources. Of the abovementioned 3 steps, amplification of target DNA/RNA is the most important. Therefore, the loop-mediated isothermal amplification (LAMP) method involving the calcein detection method has been applied to the platform as a key technology. LAMP, using the calcein method, enables recognition of small quantities of DNA/RNA of pathogens present in clinical specimens by means of the fluorescence emitted from the LAMP solutions after amplification. The next important step is sample processing, for which we have developed a simple and easy-to-use technology, namely, procedure for ultra rapid extraction (PURE). The combination of both these technologies can be considered a novel platform for molecular diagnostics, which can be applied to resource-limited settings. The fundamental characteristics of these element technologies and application of the novel platform to diagnostics for evaluation of certain tropical diseases are discussed below.