Multibead-based immunoassay provides one-step species-specific serodiagnosis of filarial infections and Strongyloides stercoralis in travelers and immigrants.

BACKGROUND: Previously, antifilarial antibody testing in the evaluation of returned travelers and immigrants to North America has relied on IgG- and IgG4-specific responses to crude filarial extracts (BmA), tests that suffer from significant cross-reactivity with Strongyloides and cannot distinguish among the infecting filarial species. Nevertheless, between 1992 and 2016 we have tested >11000 samples from providers across North America in whom a filarial infection was being considered; close to 20% were able to be definitively diagnosed with a filarial infection (based on IgG4 anti-BmA reactivity) and ∼50% had the diagnosis excluded (based on IgG anti-BmA seronegativity).

METHODS: To create an all-in-one assay for screening travelers and immigrants where infections with filariae or Strongyloides stercoralis are being considered, we configured a multibead-based assay to measure simultaneously the IgG and IgG4 responses to BmA and to the species-specific recombinants Ll-SXP1, Ov-16, OvOC3261, Wb-123, Wb5, Ss-NIE and Ss-IR.

RESULTS: By tuning the assays to >98% specificity for the species of interest (using ROC-based cutoffs), we have utilized this new assay to prospectively test samples from 1865 unique patients. Based on a hierarchical algorithm among the 318 (17%) seropositive samples, we were able to provide a species-specific diagnosis (Loa loa [N=99], Wuchereria bancrofti [N=29], Onchocerca volvulus [N=32], and S. stercoralis [N=93]) in 80%. We were able to exclude any of these organisms in 1547 (83%) based on parasite antigen-specific seronegativity.

CONCLUSION: These data provide a new framework for clinically useful parasite-specific serology that helps to direct targeted therapeutic options.