Abstract
BackgroundDetection 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.MethodsWe 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.ResultsOur 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.ConclusionsThe 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.
Highlights
Diagnosis of HIV infection by timely HIV screening is one of the cornerstones of prevention of secondary transmission and an opportunity to initiate potentially beneficial, early antiretroviral treatment [1,2]
virus-like particles (VLPs) panel characteristics Our aim was to create a VLP panel representing the wide variety of HIV-1 sequences in the gag region
By replacing gag of the vector-encoded viral genome with the respective sequences from different clades of HIV-1, we generated VLPs which contained all the structural proteins from the clades of our choice, while the RT of the particles originated from the subtype B backbone plasmid
Summary
Diagnosis of HIV infection by timely HIV screening is one of the cornerstones of prevention of secondary transmission and an opportunity to initiate potentially beneficial, early antiretroviral treatment [1,2]. The most economical way to diagnose early infection is by p24 antigen; screening tests that detect both antibodies and p24 antigen, so called 4th generation or combination screening tests, were introduced into routine testing more than 15 years ago in Europe [9] and, more recently, in the USA [10]. These tests have led to an increase in the identification of early HIV infections, attributed to the detection of p24 [9,11,12]. We aimed to create an inexhaustible panel of diverse HIV-1 p24 antigens
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