**5. New biotechnological tools in the diagnosis of leprosy**

#### **5.1. Mapping of new markers**

Many studies have used post genomic procedures for the discovery of new antigens that can be used in the diagnosis of leprosy [71–75]. These studies have explored sequences of *M. leprae* for the identification of proteins or peptides that can be used in the serodiagnosis of the different clinical forms of leprosy [76].

type of transducer used [90]. There are still specific classes of biosensors such as immunosensors [91], which evaluate interactions between antibodies and antigens, and genosensores,

Molecular and Biotechnological Approaches in the Diagnosis of Leprosy

http://dx.doi.org/10.5772/intechopen.75506

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There is a wide range of studies showing the efficacy of biosensors for the detection of various diseases such as leishmaniasis, bacterial diseases, cystic fibrosis, dengue and leprosy itself [92– 96]. In Brazil, a genosensor for *M. leprae* was constructed using the immobilization of a bacillus single-stranded DNA (ssDNA) on functionalized graphite electrodes. The interaction between the immobilized sequence and *M. leprae* double-stranded DNA (dsDNA) is measured electrochemically by reductions in the peak oxidation current and using ferrocenecarboxyaldehyde as the hybridization indicator. The result was very promising, showing efficient detection in only 3

Currently, Brazilian research groups are betting on the use of electrochemical biosensors as an indispensable tool in the diagnosis and control of diseases. This innovation is mainly because these sensors are sensitive, reliable, fast response and operate in conditions that pretreat the samples. In addition, these techniques are capable of providing exceptionally low

In this scenario, mimetic peptides of proteins and glycolipids present in the bacillus capsule have been validated for the immunogenic potential and immobilized in these electrochemical detection platforms. Thus, the proposals consist of using different biological fluids such as blood, secretion and saliva, ensuring a less invasive and more comfortable test to the patient and the manipulator. Subsequently, these platforms will be tested in hyperendemic areas, in order to evaluate their detection potential and help in the epidemiological control of the disease.

The early diagnosis of leprosy is one of the goals of the WHO for the control and reduction of new cases of the disease. This strategy will be implemented with the development of new diagnostic tools more sensitive and can be applied in large-scale monitoring. Molecular techniques and new biotechnological approaches can be used as complementary tests.The qualitative PCR, RLEP and real time PCR have been used for the detection of *M. leprae* in samples of

Immunodiagnosis can be done using different native *M. leprae* antigens such as PGL-1, LAM or their synthetic derivatives. Post-genomic technologies can be used for the production of recombinant chimeric proteins, peptides obtained in silico or mimetic peptides. Immunodiagnosis

Biotechnology and molecular biology have contributed to the development of research and improve the diagnosis of leprosy. Significant advances in laboratory diagnosis contribute to

based on the hybridization of DNA-specific ribbons [87].

different tissues of patients or of household contacts.

can be performed by ELISA, lateral flow tests and biological sensors.

minutes [87, 88, 96].

detection limits.

**6. Conclusion**

improving clinical practice.

The antigens ML0405, ML2331 and ML2055—the first two of previously unknown function and the latter a membrane protein - were used for serological tests in in multibacillary patients of the clinical forms boderline lepromatous (BL) and LL untreated [77]. The ML0308 and ML2498 proteins, a conserved hypothetical protein and an enoyl-CoA hydratase respectively, showed humoral and cellular immunogenicity and can be used in the diagnosis of tuberculoid and lepromatous forms [78]. These antigens were used in the production of fusion proteins, such as LID-1 (leprosy IDRI diagnostic-1) [42] and PADL [45, 79].

The tools of bioinformatics, genomic analysis and proteomics are also being used for mapping in silico of important antigenic targets of *M. leprae* [80]. This type of analysis was used to define a group of 50 potential antigens in mycobacteria, some being restricted to *M. leprae* [78].

Peptides derived from specific and immunogenic proteins of *M. leprae* have also been tested in patients with leprosy and controls [81]. Peptides obtained of proteins from *M. leprae* were promising as indicators of exposure [82].

The peptides are small in size and can be expressed on the surface of bacteriophage to select peptides that mimic different targets (pathogens, cellular receptors or antibodies) [83]. Mimetic peptides may have important applications in the diagnosis of leprosy, mimicking antigens such as PGL-1 [84] or other *M. leprae* antigens [85, 86]. Alternatively, due to their versatility to perform the same functions as the protein and non-protein natural antigens, mimetic peptides are considered an important tool in immunodiagnostic of infectious disease.

#### **5.2. Biosensors as platforms for the diagnosis of leprosy.**

The post-genomic, the identification and obtainment of hundreds of molecules with immunogenic potential have broadened the versatility of detection platforms and contributed to an optimal diagnostic test, especially for tropical diseases [87]. In recent decades, biosensors have been gaining more space in scientific research and diagnosis of various diseases [88].

Biosensors are analytical devices that have specific reactions and/or specific interactions mediated by a diversity of components (antigens, antibodies, enzymes, DNA fragments, organelles, receptors and even mimetic peptides) that, in contact with a transducer, have the conversion of a biological signal-a result of the interaction between specific components-in a measurable signal proportional to the analyte concentration [89]. These platforms can be electrochemical, piezoelectric, thermal, optical and based on surface plasmon resonance, depending on the type of transducer used [90]. There are still specific classes of biosensors such as immunosensors [91], which evaluate interactions between antibodies and antigens, and genosensores, based on the hybridization of DNA-specific ribbons [87].

There is a wide range of studies showing the efficacy of biosensors for the detection of various diseases such as leishmaniasis, bacterial diseases, cystic fibrosis, dengue and leprosy itself [92– 96]. In Brazil, a genosensor for *M. leprae* was constructed using the immobilization of a bacillus single-stranded DNA (ssDNA) on functionalized graphite electrodes. The interaction between the immobilized sequence and *M. leprae* double-stranded DNA (dsDNA) is measured electrochemically by reductions in the peak oxidation current and using ferrocenecarboxyaldehyde as the hybridization indicator. The result was very promising, showing efficient detection in only 3 minutes [87, 88, 96].

Currently, Brazilian research groups are betting on the use of electrochemical biosensors as an indispensable tool in the diagnosis and control of diseases. This innovation is mainly because these sensors are sensitive, reliable, fast response and operate in conditions that pretreat the samples. In addition, these techniques are capable of providing exceptionally low detection limits.

In this scenario, mimetic peptides of proteins and glycolipids present in the bacillus capsule have been validated for the immunogenic potential and immobilized in these electrochemical detection platforms. Thus, the proposals consist of using different biological fluids such as blood, secretion and saliva, ensuring a less invasive and more comfortable test to the patient and the manipulator. Subsequently, these platforms will be tested in hyperendemic areas, in order to evaluate their detection potential and help in the epidemiological control of the disease.
