Field-Evaluation of a New Lateral Flow Assay for Detection of Cellular and Humoral Immunity against Mycobacterium leprae

Background:field-applicable tests detecting asymptomatic mycobacterium leprae (m. leprae) infection or predicting progression to leprosy,are urgently required. since the outcome of m. leprae infection is determined by cellular- and humoral immunity,we aim to develop diagnostic tests detecting pro-/anti-inflammatory and regulatory cytokines as well as antibodies against m. leprae. previously,we developed lateral flow assays (lfa) for detection of cytokines and anti-pgl-i antibodies. here we evaluate progress of newly developed lfas for applications in resource-poor settings.methods:the combined diagnostic value of ip-10,il-10 and anti-pgl-i antibodies was tested using m. leprae-stimulated blood of leprosy patients and endemic controls (ec). for reduction of the overall test-to-result time the minimal whole blood assay time required to detect distinctive responses was investigated. to accommodate lfas for field settings,dry-format lfas for ip-10 and anti-pgl-i antibodies were developed allowing storage and shipment at ambient temperatures. additionally,a multiplex lfa-format was applied for simultaneous detection of anti-pgl-i antibodies and ip-10. for improved sensitivity and quantitation upconverting phosphor (ucp) reporter technology was applied in all lfas.results:single and multiplex ucp-lfas correlated well with elisas. the performance of dry reagent assays and portable,lightweight ucp-lf strip readers indicated excellent field-robustness. notably,detection of ip-10 levels in stimulated samples allowed a reduction of the whole blood assay time from 24 h to 6 h. moreover,ip-10/il-10 ratios in unstimulated plasma differed significantly between patients and ec,indicating the feasibility to identify m. leprae infection in endemic areas.conclusions:dry-format ucp-lfas are low-tech,robust assays allowing detection of relevant cytokines and antibodies in response to m. leprae in the field. the high levels of ip-10 and the required shorter whole blood assay time,render this cytokine useful to discriminate between leprosy patients and ec. © 2014 bobosha et al.