ANALYSIS OF LONG-TERM VIRAL EXPRESSION IN CEM CELLS PERSISTENTLY INFECTED WITH NON SYNCYTIUM-INDUCING HIV-1 STRAINS

CEM cells were infected with three HIV-1 non syncytium-inducing (NSI) strains obtained from AIDS patients or seropositive individuals. The s urviving cells were followed for several months in the persistently in fected cultures designated 65870/CEM, 65871/CEM and 39291/CEM, and ana lyzed for virus expression using light and electron microscopy, immuno fluorescence, reverse transcriptase assay, polymerase chain reaction a mplification (PCR), nucleic acid hybridization and flow cytometry. The virus isolates induced relatively few syncytia and other cytopathic e ffects in the corresponding cell lines and the number of cells positiv e for virus expression never rose above 44%. Distinct peaks of antigen -positive cells were obtained, coincident with high levels of reverse transcriptase activity. The cultures were strongly resistant to superi nfection by laboratory strain Lai, with the exception of 65870/CEM whi ch expressed HIV antigens in up to 15% of the cells for a few days. Ho wever, cell lysis was minimal in all cases. After long-term cultivatio n of the three cultures, no antigen-positive cells were detected and n o trace of virus expression could be observed. The remaining cells con sisted entirely of CD4-negative cells. PCR analyses indicated that cel ls harboring a provirus were progressively eliminated from the culture s, leaving only virus-free cells. In this system, cells carrying a lat ent provirus survive for a limited period of time before virus activat ion induces cell lysis. These results suggest that at least three type s of cells exist in the CEM cell line: CD4-positive cells which are ra pidly killed by the virus, a second type harboring a latent viral geno me after the infection and which grow normally until activation of the resident genome by external or internal signal(s), and a third type w hich represents rare CD4-negative cells present in the initial CEM pop ulation and which are selected for by the NSI isolates. This is the fi rst study documenting specific interactions between NSI strains of HIV -1 and distinct subpopulations of CEM cells grown as a single cell cul ture.