Performance of five different assays for the quantification of viral load in persons infected with various subtypes of HIV-1

Five methods for the assessment of plasma viral load (VL) were evaluated in 103 seropositive patients infected with various subtypes of HIV-1. The met hods included three RNA-based assays (Amplicor Monitor 1.5, Quantiplex vers ion 2.0, NucliSens), one ultrasensitive reverse transcriptase (PERT) assay and one "boosted" p24 antigen (Ag) enzyme immunoassay (EIA). Subtyping was based on sequencing in env. The sensitivities were, in decreasing order, Am plicor > PERT > p24 Ag > NucliSens > Quantiplex. The low sensitivity of Nuc liSens was related to the missing of several non-B (A, E, F, G) or recombin ant strains, whereas that of Quantiplex did not depend on subtype. In the 1 group O sample and 4 group M samples, only PERT assay or p24Ag EIA produce d a positive result. In the quantitative range, correlation was best betwee n Amplicor and Quantiplex (r = 0.8848), fair between Amplicor and NucliSens (r = 0.7064) or PERT assay (r = 0.7266), lowest between Amplicor and p24Ag EIA (r = 0.3989). Amplicor underestimated VL in 1 subtype E sample. Thus, Amplicor performed best in terms of sensitivity (compared with all other as says) and accuracy (compared with NucliSens, PERT assay, and p24Ag) for non -B subtypes in group M samples. PERT assay appears useful for VL assessment in infections by group O or other highly divergent viruses.