CONSTITUTIVE PRODUCTION OF NONENVELOPED HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 PARTICLES BY A MAMMALIAN-CELL LINE AND EFFECTS OF A PROTEASE INHIBITOR ON PARTICLE MATURATION

A stable cell line encoding the sequences of all the human immunodefic iency virus type 1 proteins, with the exception of the gp160 envelope glycoprotein, was derived from transfection of monkey COS-7 cells. Thi s cell line, referred to as CH-1, produces active viral protease that correctly processes its natural substrates and yields capsid particles . These particles contain reverse transcriptase activity and packaged viral RNA but are noninfectious. The level of expression of viral prot eins is not toxic to the cells, yet it is comparable to that observed for chronically infected lymphocytes. These constitutively synthesized viral proteins provide a consistent system for the analysis of potent ial inhibitors of late viral functions. The lack of gp160 increases th e biosafety of this assay system, while it allows the measurement of t he effects on the production and release of capsid particles, A human immunodeficiency virus type 1 protease inhibitor was used to confirm t he viral polyprotein maturation pathway in this system. Particles from cells treated with this protease inhibitor contain unprocessed p55(ga g) precursor and have the same density as the mature particles. These immature particles contain viral RNA, but reverse transcriptase activi ty is significantly reduced. This cell line may serve to identify comp ounds that are able to affect viral assembly and maturation as well as to identify the interactions between the viral and cellular proteins involved in these essential processes.