title: A Recombinant Positive Control for Serology Diagnostic Tests Supporting Elimination of Onchocerca volvulus.
abstract: BACKGROUND
  Serological assays for human IgG4 to the Onchocerca volvulus antigen Ov16 have been used to confirm elimination of onchocerciasis in much of the Americas and parts of Africa. A standardized source of positive control antibody (human anti-Ov16 IgG4) will ensure the quality of surveillance data using these tests.
  
  
  RESULTS
  A recombinant human IgG4 antibody to Ov16 was identified by screening against a synthetic human Fab phage display library and converted into human IgG4. This antibody was developed into different positive control formulations for enzyme-linked immunosorbent assay (ELISA) and rapid diagnostic test (RDT) platforms. Variation in ELISA results and utility as a positive control of the antibody were assessed from multiple laboratories. Temperature and humidity conditions were collected across seven surveillance activities from 2011-2014 to inform stability requirements for RDTs and positive controls. The feasibility of the dried positive control for RDT was evaluated during onchocerciasis surveillance activity in Togo, in 2014. When the anti-Ov16 IgG4 antibody was used as a standard dilution in horseradish peroxidase (HRP) and alkaline phosphatase (AP) ELISAs, the detection limits were approximately 1ng/mL by HRP ELISA and 10ng/mL by AP ELISA. Positive control dilutions and spiked dried blood spots (DBS) produced similar ELISA results. Used as a simple plate normalization control, the positive control antibody may improve ELISA data comparison in the context of inter-laboratory variation. The aggregate temperature and humidity monitor data informed temperature parameters under which the dried positive control was tested and are applicable inputs for testing of diagnostics tools intended for sub-Saharan Africa. As a packaged positive control for Ov16 RDTs, stability of the antibody was demonstrated for over six months at relevant temperatures in the laboratory and for over 15 weeks under field conditions.
  
  
  CONCLUSIONS
  The recombinant human anti-Ov16 IgG4 antibody-based positive control will benefit inter-laboratory validation of ELISA assays and serve as quality control (QC) reagents for Ov16 RDTs at different points of the supply chain from manufacturer to field use.
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Allison
authors.initials: A
authors.lastname: Golden
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Eric J
authors.initials: EJ
authors.lastname: Stevens
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Lindsay
authors.initials: L
authors.lastname: Yokobe
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Dunia
authors.initials: D
authors.lastname: Faulx
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Michael
authors.initials: M
authors.lastname: Kalnoky
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Roger
authors.initials: R
authors.lastname: Peck
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Melissa
authors.initials: M
authors.lastname: Valdez
authors.affiliation: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Cathy
authors.initials: C
authors.lastname: Steel
authors.affiliation: National Onchocerciasis Control Programme, Kara, Togo.
authors.forename: Potochoziou
authors.initials: P
authors.lastname: Karabou
authors.affiliation: Onchocerciasis Reference Laboratory, National Institute of Hygiene, Sokodé, Togo.
authors.forename: Méba
authors.initials: M
authors.lastname: Banla
authors.affiliation: Onchocerciasis Reference Laboratory, National Institute of Hygiene, Sokodé, Togo.|Institute of Tropical Medicine, University Clinics of Tübingen, Tübingen, Germany.
authors.forename: Peter T
authors.initials: PT
authors.lastname: Soboslay
authors.affiliation: National Onchocerciasis Control Programme, Kara, Togo.
authors.forename: Kangi
authors.initials: K
authors.lastname: Adade
authors.affiliation: African Programme for Onchocerciasis Control, World Health Organization, Ouagadougou, Burkina Faso.
authors.forename: Afework H
authors.initials: AH
authors.lastname: Tekle
authors.affiliation: Division of Parasitic Diseases and Malaria, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America.
authors.forename: Vitaliano A
authors.initials: VA
authors.lastname: Cama
authors.affiliation: Department of Internal Medicine, Infectious Diseases Division, Washington University School of Medicine, St. Louis, Missouri, United States of America.
authors.forename: Peter U
authors.initials: PU
authors.lastname: Fischer
authors.affiliation: Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland, United States of America.
authors.forename: Thomas B
authors.initials: TB
authors.lastname: Nutman
authors.affiliation: Global Health Infectious Disease Research Program, Department of Global Health, University of South Florida, Tampa, Florida, United States of America.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Unnasch
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Tala
authors.initials: T
authors.lastname: de los Santos
authors.affiliation: Diagnostics Global Program, PATH, Seattle, Washington, United States of America.
authors.forename: Gonzalo J
authors.initials: GJ
authors.lastname: Domingo
mesh_terms: D000818:Animals; D000909:Antibodies, Helminth / Q000097:blood* / Q000235:genetics; D000947:Antigens, Helminth / Q000235:genetics / Q000276:immunology*; D003955:Diagnostic Tests, Routine / Q000379:methods / Q000592:standards*; D004797:Enzyme-Linked Immunosorbent Assay / Q000379:methods / Q000592:standards; D006801:Humans; D017181:Onchocerca volvulus / Q000276:immunology*; D009855:Onchocerciasis / Q000175:diagnosis* / Q000628:therapy; D010865:Pilot Projects; D011994:Recombinant Proteins / Q000235:genetics / Q000276:immunology; D012015:Reference Standards; D012698:Serologic Tests / Q000379:methods / Q000592:standards*; D014037:Togo; D016896:Treatment Outcome
chemical_list: D000909:Antibodies, Helminth; D000947:Antigens, Helminth; D011994:Recombinant Proteins