COMPARISON OF P24 MEASUREMENT BY ELISA VERSUS INDICATOR CELLS FOR DETECTING RESIDUAL HIV INFECTIVITY IN-VITRO

Inactivation of HIV-1 contaminated materials or biological samples is of great importance and requires the use of a reliable assay to detect residual infectivity. In this study we treated cell-free or cell-asso ciated (monocyte-derived macrophages) HIV-1 with two chemicals known f or their antiviral activities, beta-propiolactone (beta PL) and formal dehyde (FO), and tested it for the presence of residual infectivity. H IV-1 infected primary monocyte-derived macrophages (MDM) or cell-free HIV-1 were fixed with increasing concentrations of either beta PL or F O for 1 day al 4 degrees C. Then either fresh primary MDM or fresh med ium was added, and the supernatant p24 levels were assayed up to 12 da ys after infection. All the supernatants harvested were added to indic ator cells, fresh primary MDM, to assess for residual infectivity. The results show that p24 measurement is not a reliable assay for the det ection of residual infectious virions after chemical fixation of HIV-i nfected primary MDM. In contrast, the use of indicator primary cells ( MDM) is a much more sensitive and reliable assay. By performing an ind icator cell assay we showed that FO efficiently inactivates cell-assoc iated and cell-free HIV-1 at concentrations as low as 1% v/v. In contr ast beta PL is more efficient in inactivating cell-free than cell-asso ciated virus and does not inactivate cell-associated HIV-1 at concentr ations as high as 1% v/v.