Potential antigenic targets used in immunological tests for diagnosis of tegumentary leishmaniasis: A systematic review

Abstract

Immunological tests may represent valuable tools for the diagnosis of human tegumentary leishmaniasis (TL) due to their simple execution, less invasive nature and potential use as a point-of-care test. Indeed, several antigenic targets have been used with the aim of improving the restricted scenario for TL-diagnosis. We performed a worldwide systematic review to identify antigenic targets that have been evaluated for the main clinical forms of TL, such as cutaneous (CL) and mucosal (ML) leishmaniasis. Included were original studies evaluating the sensitivity and specificity of immunological tests for human-TL, CL and/or ML diagnosis using purified or recombinant proteins, synthetic peptides or polyclonal or monoclonal antibodies to detect Leishmania-specific antibodies or antigens. The review methodology followed PRISMA guidelines and all selected studies were evaluated in accordance with QUADAS-2. Thirty-eight original studies from four databases fulfilled the selection criteria. A total of 79 antigens were evaluated for the detection of antibodies as a diagnostic for TL, CL and/or ML by ELISA. Furthermore, three antibodies were evaluated for the detection of antigen by immunochromatographic test (ICT) and immunohistochemistry (IHC) for CL-diagnosis. Several antigenic targets showed 100% of sensitivity and specificity, suggesting potential use for TL-diagnosis in its different clinical manifestations. However, a high number of proof-of-concept studies reinforce the need for further analysis aimed at verifying true diagnostic accuracy in clinical practice.

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“…In contrast, a systematic review by Zanetti et al revealed that more specific (recombinant) antigens yielded better diagnosis results, that is, sensitivity (93.8–100%) and specificity (82.5–100%) for ATL, compared with crude soluble antigen-based ELISAs [ 27 ]. More than 70 different antigens have been evaluated as ELISA diagnostic markers for (M)CL [ 28 ]. For example, an ELISA based on a recombinant conserved Leishmania hypothetical protein (which showed a high amino acid sequence homology between CL- as well as VL-causing Leishmania species) was found to be more specific and sensitive in detecting (M)CL patients than an ELISA based on L. braziliensis soluble antigens [ 29 ].…”

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“…ELISA, because of its high sensitivity and specificity, remains a major method, although the choice of antigen can influence sensitivity, requiring well-equipped facilities. The immunochromatographic test (ICT) using the rK39 antigen constitutes a rapid, economical, and non-invasive screening test for visceral leishmaniasis, remaining effective for large-scale screening despite variations in performance between epidemiological populations [ 43 ].…”

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“…Nevertheless, recent guidance from the WHO Diagnostic Technical Advisory Group for neglected tropical diseases (NTDs) highlights the need to develop new point-of-care tests for Cutaneous Leishmaniasis (CL). The currently available CL Detect Rapid Test fails to meet the requisite diagnostic performance standards of reaching 95% sensitivity for point-of-care waiting for the next generation of CL-RDT based on antigen detection that should differentiate between L.tropica, L.major, and other species [1,29,30].…”