PLoS Neglected Tropical Diseases (May 2014)

Field-evaluation of a new lateral flow assay for detection of cellular and humoral immunity against Mycobacterium leprae.

  • Kidist Bobosha,
  • Elisa M Tjon Kon Fat,
  • Susan J F van den Eeden,
  • Yonas Bekele,
  • Jolien J van der Ploeg-van Schip,
  • Claudia J de Dood,
  • Karin Dijkman,
  • Kees L M C Franken,
  • Louis Wilson,
  • Abraham Aseffa,
  • John S Spencer,
  • Tom H M Ottenhoff,
  • Paul L A M Corstjens,
  • Annemieke Geluk

DOI
https://doi.org/10.1371/journal.pntd.0002845
Journal volume & issue
Vol. 8, no. 5
p. e2845

Abstract

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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.