DETECTION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 (HIV-1) RNA IN POOLSOF SERA NEGATIVE FOR ANTIBODIES TO HIV-1 AND HIV-2

A total of 234 pools were prepared from 10,692 consecutive serum sampl es negative for antibodies to human immunodeficiency virus type 1 (HIV -I) and HIV-2 collected at five virological laboratories (average pool size, 45 serum samples). Pools were screened for the presence of HIV- 1 RNA by a modified commercial assay (Amplicor HIV-1 Monitor test) whi ch included an additional polyethylene glycol (PEG) precipitation step prior to purification of viral RNA (PEG Amplicor assay). The sensitiv ity of this assay for HIV-1 RNA detection in individual serum samples within pools matches that of standard commercial assays for individual serum samples, i.e.,, 500 HIV-1 RNA copies per mi. Five pools were id entified as positive, and each one contained one antibody-negative, HI V-1 RNA-positive serum sample, corresponding to an average of 1 infect ed sample per 2,138 serum samples. Retrospective analysis revealed tha t the five HIV-1 RNA-positive specimens originated from individuals wh o had symptomatic primary HIV-1 infection at the time of sample collec tion and who were also positive for p24 antigenemia. We next assessed the possibility of performing the prepurification step by high-speed c entrifugation (50,000 x g for 80 min) of 1.5-ml pools containing 25 mu l of 60 individual serum samples, of which only 1 contained HIV-1 RNA (centrifugation Amplicor assay). The sensitivity of this assay also m atches the sensitivities of standard commercial assays for HIV-1 RNA d etection in individual serum samples, The results demonstrate that bot h assays with pooled sera can be applied to the screening of large num bers of serum samples in a time-and cost-efficient manner.