Evaluation of the Diagnostic Performance of Onchocerca volvulus Linear Epitopes in a Peptide Enzyme-Linked Immunosorbent Assay

Abstract

Abstract.Diagnostic tools for the detection of infection with Onchocerca volvulus are presently limited to microfilaria detection in skin biopsies and serological assessment using the Ov16 immunoglobulin G4 (IgG4) rapid test, both of which have limited sensitivity. We have investigated the diagnostic performance of a peptide enzyme-linked immunosorbent assay (ELISA) based on immunodominant linear epitopes previously discovered. Peptides that were used in these assays were designated O. volvulus motif peptides (OvMP): OvMP-1 (VSV-EPVTTQET-VSV), OvMP-2 (VSV-KDGEDK-VSV), OvMP-3 (VSV-QTSNLD-VSV), and the combination of the latter two, OvMP-23 (VSV-KDGEDK-VSV-QTSNLD-VSV). Sensitivity (O. volvulus infection), specificity (non-helminth infections), and cross-reactivity (helminth infections) were determined using several panels of clinical plasma isolates. OvMP-1 was found to be very sensitive (100%) and specific (98.7%), but showed substantial cross-reactivity with other helminths. Of the other peptides, OvMP-23 was the most promising peptide with a sensitivity of 92.7%, a specificity of 100%, and a cross-reactivity of 6%. It was also demonstrated that these peptides were immunoreactive to IgG but not IgG4, and there is no correlation with the Ov16 IgG4 status, making them promising candidates to complement this already available test. Combination of the Ov16 IgG4 rapid test and OvMP-23 peptide ELISA led to a sensitivity of 97.3% for the detection of O. volvulus infection, without compromising specificity and with minimal impact on cross-reactivity. The available results open the opportunity for a “clinical utility use case” discussion for improved O. volvulus epidemiological mapping.

Patent infections with soil-transmitted helminths and Schistosoma mansoni are not associated with increased prevalence of antibodies to the Onchocerca volvulus peptide epitopes OvMP-1 and OvMP-23

“…C-terminally biotinylated synthetic peptides OvMP-1 (VSV-EPVTTQET-VSV) and OvMP-23 (VSV-KDGEDK-VSV-QTSNLD-VSV) were synthesized by standard procedures and purchased from PEPperPRINT GmbH (Heidelberg, Germany). For determination of peptide specific serum antibody levels, a peptide ELISA was developed and set up as described previously [18, 26]. The cut-offs for OvMP-1 and OvMP-23 were previously determined and were set at background-corrected OD values of 0.045 and 0.110, respectively [18].…”

“…Recently, two peptide-based serology markers (OvMP-1 and OvMP-23) were described and their diagnostic performance evaluated [18]. Both peptides showed high diagnostic sensitivity (100% and 92.7%, respectively) and specificity (98.7% and 100%, respectively).…”

In Silico Design and Validation of OvMANE1, a Chimeric Antigen for Human Onchocerciasis Diagnosis

“…Analysis of the total IgG response to OvMANE1 chimeric antigen revealed its ability to differentiate between infected and non-infected individuals. The specificity of a test is of high importance [ 37 ]: thus, a cutoff value of 0.456 was defined for OvMANE1 chimeric antigen that corresponds to 100% specificity and 98% sensitivity. With these settings, the chimeric antigen discriminated between ongoing infections and treated cases.…”

“…Reports indicate that the humoral immune response against parasitic antigens is frequently dominated by IgG4 responses [ 37 , 39 ]. Thus, IgG4 responses to the constituents of OvMANE1 chimeric antigen were evaluated using serum pools from infected and non-infected individuals.…”

Operational Performance of the Onchocerca volvulus “OEPA” Ov16 ELISA Serological Assay in Mapping, Guiding Decisions to Stop Mass Drug Administration, and Posttreatment Surveillance Surveys

“…Adaptation of LIPS technology to the detection of antibodies to Ov16 and the use of other antigens has shown promise in this regard. 27,28 Ideally, these assays may be available to replace the skin snip PCR as a confirmatory assay in the near future.…”