Identification of sVSG117 as an Immunodiagnostic Antigen and Evaluation of a Dual-Antigen Lateral Flow Test for the Diagnosis of Human African Trypanosomiasis
2014
Background The diagnosis of human
African trypanosomiasis(HAT) caused by
Trypanosoma brucei gambienserelies mainly on the Card Agglutination Test for
Trypanosomiasis(CATT). There is no
immunodiagnosticfor HAT caused by T. b. rhodesiense. Our principle aim was to develop a prototype
lateral flow testthat might be an improvement on CATT. Methodology/Principle Findings Pools of infection and control sera were screened against four different soluble form variant surface glycoproteins (sVSGs) by ELISA and one, sVSG117, showed particularly strong immunoreactivity to pooled infection sera. Using individual sera, sVSG117 was shown to be able to discriminate between T. b. gambiense infection and control sera by both ELISA and
lateral flow test. The sVSG117 antigen was subsequently used with a previously described recombinant diagnostic antigen, rISG65, to create a dual-antigen
lateral flow testprototype. The latter was used blind in a virtual
field trialof 431 randomized infection and control sera from the WHO HAT Specimen
Biobank. Conclusion/Significance In the virtual
field trial, using two positive antigen bands as the criterion for infection, the sVSG117 and rISG65 dual-antigen
lateral flow testprototype showed a sensitivity of 97.3% (95% CI: 93.3 to 99.2) and a specificity of 83.3% (95% CI: 76.4 to 88.9) for the detection of T. b. gambiense infections. The device was not as good for detecting T. b. rhodesiense infections using two positive antigen bands as the criterion for infection, with a sensitivity of 58.9% (95% CI: 44.9 to 71.9) and specificity of 97.3% (95% CI: 90.7 to 99.7). However, using one or both positive antigen band(s) as the criterion for T. b. rhodesiense infection improved the sensitivity to 83.9% (95% CI: 71.7 to 92.4) with a specificity of 85.3% (95% CI: 75.3 to 92.4). These results encourage further development of the dual-antigen device for clinical use.
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