title: Generation of a recombinant Gag virus-like-particle panel for the evaluation of p24 antigen detection by diagnostic HIV tests.
abstract: BACKGROUND
  Detection of HIV-1 p24 antigen permits early identification of primary HIV infection and timely intervention to limit further spread of the infection. Principally, HIV screening should equally detect all viral variants, but reagents for a standardised test evaluation are limited. Therefore, we aimed to create an inexhaustible panel of diverse HIV-1 p24 antigens.
  
  
  METHODS
  We generated a panel of 43 recombinantly expressed virus-like particles (VLPs), containing the structural Gag proteins of HIV-1 subtypes A-H and circulating recombinant forms (CRF) CRF01_AE, CRF02_AG, CRF12_BF, CRF20_BG and group O. Eleven 4th generation antigen/antibody tests and five antigen-only tests were evaluated for their ability to detect VLPs diluted in human plasma to p24 concentrations equivalent to 50, 10 and 2 IU/ml of the WHO p24 standard. Three tests were also evaluated for their ability to detect p24 after heat-denaturation for immune-complex disruption, a pre-requisite for ultrasensitive p24 detection.
  
  
  RESULTS
  Our VLP panel exhibited an average intra-clade p24 diversity of 6.7%. Among the 4th generation tests, the Abbott Architect and Siemens Enzygnost Integral 4 had the highest sensitivity of 97.7% and 93%, respectively. Alere Determine Combo and BioRad Access were least sensitive with 10.1% and 40.3%, respectively. Antigen-only tests were slightly more sensitive than combination tests. Almost all tests detected the WHO HIV-1 p24 standard at a concentration of 2 IU/ml, but their ability to detect this input for different subtypes varied greatly. Heat-treatment lowered overall detectability of HIV-1 p24 in two of the three tests, but only few VLPs had a more than 3-fold loss in p24 detection.
  
  
  CONCLUSIONS
  The HIV-1 Gag subtype panel has a broad diversity and proved useful for a standardised evaluation of the detection limit and breadth of subtype detection of p24 antigen-detecting tests. Several tests exhibited problems, particularly with non-B subtypes.
authors.affiliation: Swiss National Center for Retroviruses (SNCR), Institute of Medical Virology, University of Zürich, Zürich, Switzerland.
authors.forename: Beatrice N
authors.initials: BN
authors.lastname: Vetter
authors.affiliation: Swiss National Center for Retroviruses (SNCR), Institute of Medical Virology, University of Zürich, Zürich, Switzerland.
authors.forename: Vanessa
authors.initials: V
authors.lastname: Orlowski
authors.affiliation: Institute of Tropical Medicine (ITG), Clinical Science, Antwerp, Belgium.
authors.forename: Katrien
authors.initials: K
authors.lastname: Fransen
authors.affiliation: Blood Transfusion Service, Swiss Red Cross Berne (BSDSRK), Berne, Switzerland.
authors.forename: Christoph
authors.initials: C
authors.lastname: Niederhauser
authors.affiliation: University Hospital, Service of Immunology and Allergy, CHUV, Lausanne, Switzerland.
authors.forename: Vincent
authors.initials: V
authors.lastname: Aubert
authors.affiliation: Labor Synlab Luzern, Lucerne, Switzerland.
authors.forename: Marcel
authors.initials: M
authors.lastname: Brandenberger
authors.affiliation: Viollier AG, Allschwil, Switzerland.
authors.forename: Diana
authors.initials: D
authors.lastname: Ciardo
authors.affiliation: Center for Laboratory Medicine (ZLMSG), St. Gallen, Switzerland.
authors.forename: Günter
authors.initials: G
authors.lastname: Dollenmaier
authors.affiliation: Department Biomedicine, Haus Petersplatz, University of Basel, Basel, Switzerland.
authors.forename: Thomas
authors.initials: T
authors.lastname: Klimkait
authors.affiliation: University Hospital, Clinic for Immunology, Zurich, Switzerland.
authors.forename: Stephan
authors.initials: S
authors.lastname: Regenass
authors.affiliation: Department of Infectious Diseases, Cantonal Hospital St. Gallen (KSSG), St. Gallen, Switzerland.
authors.forename: Patrick
authors.initials: P
authors.lastname: Schmid
authors.affiliation: German Red Cross Blood Transfusion Service West (DRK), Hagen, Germany.
authors.forename: Volkmar
authors.initials: V
authors.lastname: Schottstedt
authors.affiliation: University of Berne, Institute of Infectious Diseases, Berne, Switzerland.
authors.forename: Franziska
authors.initials: F
authors.lastname: Suter-Riniker
authors.affiliation: University Hospitals (HUG), Laboratory of Virology, Genève, Switzerland.
authors.forename: Sabine
authors.initials: S
authors.lastname: Yerly
authors.affiliation: Swiss National Center for Retroviruses (SNCR), Institute of Medical Virology, University of Zürich, Zürich, Switzerland.
authors.forename: Cyril
authors.initials: C
authors.lastname: Shah
authors.affiliation: Swiss National Center for Retroviruses (SNCR), Institute of Medical Virology, University of Zürich, Zürich, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Böni
authors.affiliation: Swiss National Center for Retroviruses (SNCR), Institute of Medical Virology, University of Zürich, Zürich, Switzerland.
authors.forename: Jörg
authors.initials: J
authors.lastname: Schüpbach
mesh_terms: D000595:Amino Acid Sequence; D015488:HIV Antigens / Q000302:isolation & purification*; D016655:HIV Core Protein p24 / Q000737:chemistry / Q000378:metabolism*; D015658:HIV Infections / Q000175:diagnosis*; D006801:Humans; D008969:Molecular Sequence Data; D010802:Phylogeny; D011489:Protein Denaturation; D011933:Reagent Kits, Diagnostic; D011994:Recombinant Proteins / Q000378:metabolism*; D014771:Virion / Q000378:metabolism*; D054301:gag Gene Products, Human Immunodeficiency Virus / Q000378:metabolism*
chemical_list: D015488:HIV Antigens; D016655:HIV Core Protein p24; D011933:Reagent Kits, Diagnostic; D011994:Recombinant Proteins; D054301:gag Gene Products, Human Immunodeficiency Virus