HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 RNA EXPRESSION BY 4 CHRONICALLY INFECTED CELL-LINES INDICATES MULTIPLE MECHANISMS OF LATENCY

Recent information has suggested that posttranscriptional mechanisms, whereby human immunodeficiency virus type 1 (HIV-1) RNA exists as mult iply spliced transcripts without promoting an accumulation of the larg er messages, are responsible for maintaining a stable state of nonprod uctive viral expression or viral latency. To test the universality of these observations, we compared the patterns of viral RNA splicing and the frequencies of cells actually harboring HIV-1 RNA in four chronic ally HIV-1-infectcd cell lines (U1 [promonocytic], ACH-2 [T lymphocyti c], OM-10.1 [promyelocytic], and J1.1 [T lymphocytic]). In uninduced U 1 and ACH-2 cultures, a high frequency of cells (approximately one in six) contained HIV-1 RNA but mainly as multiply spliced transcripts, a gain supporting a posttranscriptional mechanism maintaining viral late ncy. In sharp contrast, only 1 in 50 cells in uninduced OM-10.1 and J1 .1 cultures contained HIV-1 RNA, indicating a primary transcriptional mechanism controlling viral expression in these cells. Furthermore, th ose OM-10.1 and J1.1 cells that did contain viral RNA were in a state of productive HIV-1 expression marked by the presence of both spliced and unspliced transcripts. Even though the total absence of viral RNA in the majority of OM-10.1 and J1.1 cells indicated a state of absolut e latency, treatment with tumor necrosis factor alpha induced transcri ption of HIV-1 RNA in nearly 100% of the cells in all four of the chro nically infected cultures. Tumor necrosis factor alpha induction of U1 ,ACH-2, and OM-10.1 cultures resulted in an initial accumulation of mu ltiply spliced HIV-1 RNA followed by a transition to the larger unspli ced viral RNA transcripts. This RNA splice transition was less apparen t in the J1.1 cell line. These results demonstrate that host cell-spec ific transcriptional and posttranscriptional mechanisms are important factors in the control of HIV-1 latency.