CONSEQUENCES OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 SUPERINFECTION OF CHRONICALLY INFECTED-CELLS

Infection of T cell lines by the type 1 human immunodeficiency virus (HIV-1) is associated with downregulation of the CD4 receptor and resistance to further HIV-1 infection, the phenomenon of viral interference. The ACH2 cell line, a model for chronic HIV-1 infection, possesses a single integrated copy of the HIV-1 strain LAI, is essentially CD4 negative, and can be induced to make virus by a variety of stimuli. We utilized the known sequence differences between HIV(LAI) and HIV(RF) to devise a polymerase chain reaction (PCR) strategy that permits reliable and quantitative discrimination between the two strains. We demonstrate that ACH2 cells can be superinfected by HIV(RF) at a frequency of 60-300 HIV(RF) genomes/10(4) ACH2 cells and that the frequency of superinfection appears to increase with time. Reverse transcription of ACH2 mRNA from days 13, 27, and 38 postinfection allowed a similar PCR strategy (RT-PCR) to be used to analyze full-length HIV(RF-) and HIV(LAI)-specific transcripts. These data suggested that superinfection of ACH2 with HIV(RF) results in an increase in expression of both HIV(RF) and HIV(LAI) mRNA. From day 13 to day 38 postinfection there was an increase in the relative expression of HIV(RF) compared with HIV(LAI). By day 38, when only 1.1% of HIV DNA sequences were HIV(RF) derived, roughly 80% of the HIV-specific full-length mRNA was HIV(RF) in origin, with a concomitant decrease in HIV(LAI) transcription.