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

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

Author information

1
Department of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands; Armauer Hansen Research Institute, Addis Ababa, Ethiopia.
2
Department of Molecular Cell Biology, Leiden University Medical Center, Leiden, The Netherlands.
3
Department of Infectious Diseases, Leiden University Medical Center, Leiden, The Netherlands.
4
Armauer Hansen Research Institute, Addis Ababa, Ethiopia.
5
Department of Microbiology, Immunology & Pathology, Colorado State University, Fort Collins, Colorado, United States of America.

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.

PMID:
24810599
PMCID:
PMC4014418
DOI:
10.1371/journal.pntd.0002845
[Indexed for MEDLINE]
Free PMC Article

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