Reduction of the diagnostic window in three cases of human immunodeficiency-1 subtype E primary infection with fourth-generation HIV screening assays.

Background and Objectives The influence of genetic variability on the sensitivity of serological diagnosis of human immunodeficiency virus (HIV) infection has, to date, been poorly investigated. The aim of the present study was to assess whether fourth-generation assays for the combined detection of HIV antigen and antibodies to HIV (anti-HIV) permit a reduction of the diagnostic window in comparison to third-generation antibody enzyme immunoassays (EIAs), which so far have shown a poor sensitivity for detection of HIV-1 non-subtype B primary infections. Materials and Methods Three patients with primary HIV-1 subtype E (CRF01-AE) infection were tested with different third- and fourth-generation assays, stand-alone HIV antigen (Ag) EIAs and reverse transcription–polymerase chain reaction (RT–PCR). Additionally, virus lysates from HIV-1 Group M and O and HIV-2, at concentrations of p24 Ag close to the detection limit of licensed HIV Ag EIAs, were investigated with fourth-generation EIAs and HIV Ag EIAs. Results In the first blood donor, the most sensitive fourth-generation assay detected HIV-1 infection 11 days earlier than five of the eight third-generation antibody assays. Fourth-generation EIAs, with a high sensitivity for HIV antigen, detected HIV-1 subtype E infection simultaneously or 4 days later than HIV-1 RT–PCR on pooled samples. Low concentrations of virus lysates of different HIV-1 subtypes A–H and group O, tested positive with fourth-generation EIAs, with a high sensitivity of the antigen-detection module. Conclusions Fourth-generation EIAs, especially those with a high sensitivity for HIV-1 p24 antigen, reduce the diagnostic window for primary HIV-1 subtype E infection in comparison with third-generation antibody-screening assays. These preliminary data from seroconversions and virus lysates indicate that the genetic diversity of HIV-1 does not represent a major challenge for the most sensitive EIAs of this new assay generation.