Spontaneous Antigenemia in Loiasis

Spontaneous Antigenemia in Loiasis, A Study of the Loiasis Antigens Responsible for Cross-reactivity in the Rapid Diagnostic Test for Lymphatic Filariasis

This prospective study will enroll and follow 60 loiasis patients with high worm burden to monitor the spontaneous release of filarial antigen in peripheral blood. This study will define the cross-reactive antigen profile of persons with spontaneous loiasis antigenemia, and determine whether it varies with time.

Study Overview

• Status: Completed
• Conditions: Lymphatic Filariasis; Loiasis
• Intervention / Treatment: Other: No intervention

Detailed Description

Global efforts to eradicate lymphatic filariasis (LF) depend on rapid diagnostic tests (RDTs) that detect Wuchereria bancrofti circulating filarial antigen but these tests are unreliable in African nations where Loa loa is co-endemic because they yield false-positive results in some individuals with loiasis. The goals of this project are to define the cross-reactive antigen profile of persons with spontaneous antigenemia, how it varies over time, and to determine which L. loa antigens in cross-reactive sera best distinguish loiasis cross-reactivity from LF.

This prospective study will prospectively enroll 50 adults who presented with cross-reactive antigenemia at screening and 10 negative controls. Participants will followed for one year and tested every three months for persistence of antigenemia.

• Study Type: Observational
• Enrollment (Actual): 86

Contacts and Locations

Study Locations

• Cameroon
  • Yaoundé, Cameroon
    • Centre for Research on Filariasis and other Tropical Diseases (CRFilMT)

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: 18 years and older (Adult, Older Adult)
• Accepts Healthy Volunteers: No

• Sampling Method: Non-Probability Sample

Study Population

The study will be conducted in the Okola health district (Lékié Division, Centre Region, Cameroon), situated about 40km northeast of Yaoundé, the political capital city of Cameroon. The Okola health district is highly endemic for loiasis. Participant will be recruited among those excluded from an Onchocerciasis study due to high Mf counts >20,000/mL.

Description

Inclusion Criteria:

• Ability to give informed consent
• Loiasis Mf count > 20,000 Mf/mL
• Resident of study area
• No evidence of severe or systemic comorbidities
• Consent to storage of blood samples for future study

Exclusion Criteria:

• Subject plans to move from the study area during subsequent 12 months

Study Plan

How is the study designed?

Number of groups / cohorts

2

Cohorts and Interventions

Group / Cohort	Intervention / Treatment
Cross-reactive loiasis; This cohort will prospectively enroll 50 adults (age 18+) with cross-reactive antigenemia based on a positive filariasis test strip (FTS) and L. loa Mf counts >20,000 Mf/mL.	Other: No intervention; Patients in these cohorts will not be given anti-filariasis therapies because these drugs are not approved for use in patients with high worm burdens (>20,000 Mf/mL)
non-cross-reactive loiasis; This cohort will prospectively enroll 10 adults (age 18+) with a negative filariasis test strip (FTS) and L. loa Mf counts >20,000 Mf/mL.

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
prevalence of specific cross-reactive L. loa antigens at baseline	Prevalence of filariasis test strip (FTS) positive individuals at screening. Cross-reactive proteins in plasma will be identified by mass-spectrometry to identify a cross-reactive biomarker	1 day

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Recurrence of cross-reactive antigenemia	To determine if the same antigens are present at each follow up	quarterly for 1 year

Collaborators and Investigators

• Sponsor: Washington University School of Medicine
• Collaborators: Doris Duke Charitable Foundation; Center for Research on Filariasis and Other Tropical Diseases, Cameroon
• Investigators: Principal Investigator: Philip Budge, MD, PhD, Washington University School of Medicine

Study record dates

Study Major Dates

• Study Start (Actual): January 23, 2020
• Primary Completion (Actual): May 31, 2021
• Study Completion (Actual): May 31, 2021

Study Registration Dates

• First Submitted: February 3, 2020
• First Submitted That Met QC Criteria: February 3, 2020
• First Posted (Actual): February 6, 2020

Study Record Updates

• Last Update Posted (Actual): August 21, 2026
• Last Update Submitted That Met QC Criteria: August 18, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: cross-reactivity; diagnostics
• Additional Relevant MeSH Terms: Vector Borne Diseases; Mosquito-Borne Diseases; Infections; Parasitic Diseases; Lymphatic Diseases; Spirurida Infections; Secernentea Infections; Nematode Infections; Helminthiasis; Lymphedema; Filariasis; Hemic and Lymphatic Diseases; Elephantiasis, Filarial; Loiasis
• Other Study ID Numbers: 201909003

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: The deidentified IPD for all primary and secondary outcomes will be made publicly available either as a supplementary file in a research publication and/or made publicly available in a data repository maintained by the Becker Biomedical Library at Washington University.
• IPD Sharing Time Frame: The data will be made available following publication. It will remain available indefinitely.
• IPD Sharing Access Criteria: The data will be made publicly available.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: No
• Studies a U.S. FDA-regulated device product: No