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

PLoS Negl Trop Dis. 2014 May 8;8(5):e2845. doi: 10.1371/journal.pntd.0002845. eCollection 2014 May.

Abstract

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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antibodies, Bacterial / blood*
  • Antigens, Bacterial / immunology*
  • Cytokines / blood*
  • Cytokines / metabolism
  • Humans
  • Immunologic Tests / methods*
  • Kinetics
  • Leprosy / diagnosis*
  • Leprosy / immunology*
  • Mycobacterium leprae / immunology*

Substances

  • Antibodies, Bacterial
  • Antigens, Bacterial
  • Cytokines

Grants and funding

This work was supported by the Q. M. Gastmann-Wichers Foundation and EDCTP through a project entitled AE-TBC under Grant Agreement N° IP_09_32040. Additional funding was obtained from the Netherlands Leprosy Relief Foundation (NLR) together with the Turing Foundation (ILEP#: 701.02.49), the Heiser Program for Research in Leprosy in The New York Community Trust (P13-000392), the Order of Malta-Grants-for-Leprosy-Research (MALTALEP) and the UNICEF/UNDP/World Bank/WHO Special Programme for Research and Training in Tropical Diseases (TDR). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.