PRELIMINARY IN-VITRO GROWTH-CYCLE AND TRANSMISSION STUDIES OF HIV-1 IN AN AUTOLOGOUS PRIMARY-CELL ASSAY OF BLOOD-DERIVED MACROPHAGES AND PERIPHERAL-BLOOD MONONUCLEAR-CELLS

Recent interest focused on the dynamics of HIV-1 replication in primar y monocytes/macrophages and T-lymphocytes of the immune system, as wel l as the standardization of virological and immunological in vitro ass ays with primary isolates, provided the impetus for these studies. The se types of studies have never been performed as they would occur in v ivo, i.e., where the envelope of the virus and cell membranes of the t wo cell types of the same host origin. Therefore, the biological and p hysicochemical properties of an uncloned, primary dual-tropic isolate HIV-1(ADA) during the initial lag, log, and stationary phases of viral replication were studied in an autologous donor cell assay in periphe ral blood mononuclear cells (PBMC) and blood monocyte-derived macropha ges (MDM). Similar total numbers (10(9) virus particles/ml) were produ ced by both cell types during the stationary period. On a per cell per day basis, during peak stationary periods, 0.92 x 10(3) virions/day f or MDMs and 5.31 x 10(3) virions/day for PBMCs were produced. Interest ingly, virus replicating from MDMs during the log-growth phase demonst rated the greatest infectious fraction which was 3 logs greater than v irus replicating in PBMCs. Despite constant virus particle production in MDMs, the infectious fraction was found to fall 3 to 4 lags over a In-day period. Due to an infectious fraction less than 1 (0.053 infect ious unit/cell/24 hr), virus spread in PBMCs during the rapid log phas e could only have occurred by cell-to-cell contact, whereas in MDMs wi th an infectious fraction of about one infectious particle (similar to 1/cell/24 hr), cell-free transmission could account for the observed results. Most of the MDMs (> 90%) became productively infected, wherea s only 5-10% of the total PBMCs were found replicating virus. The peri od of peak stationary virus production (i.e., stationary phase) was at minimum 4 to 5 times longer in MDMs than PBMCs. Whereas the majority of p24, RT, and gp120 found to be associated with MDM-derived virions, no increased dissociation of these components was observed in PBMC-de rived virions. The virion-associated gp120 was 3 to 4 times more stabl e on both PBMC- and MDM-derived virus (> 96 hr) and present at 10-25 t imes the concentration per virion than that observed for a T-cell-line -adapted laboratory strain of HIV-1 replicating in T-cell lines. These in vitro results suggest that important differences exist between MDM s and PBMCs with regard to the viral dynamics of infection and replica tion which should provide for a qualitative and quantitative basis to estimate virus replication on a per-cell basis for other known cellula r targets of HIV-1. Studying the multiple biophysicochemical character istics and viral replication dynamics as described herein provides an autologous in vitro model of additional quantifiable parameters for an alysis and understanding of virus/host factor(s) and/or antivirals whi ch influence them. (C) 1996 Academic Press, Inc.