Abstract
The aim of this study was to establish human macrophage hybridoma cell lines which would be used to investigate the replication of the human immunodeficiency virus type-1 (HIV-1). Polyethylene glycol (PEG) was selected to mediate fusion between human macrophages and monocytic cell lines. Rapid methods to detect conditions favouring fusion were developed. However, despite the optimization of protocols, no macrophage hybridomas were successfully isolated. The results suggest that macrophages can exert a negative regulation on the replication capacity of hybridomas. In the absence of macrophage hybridomas, established immature monocytic cell lines were used to investigate the role of the cell cycle in the replication of HIV-1. A range of chemicals were titrated and compounds that could inhibit in G1/G0, S and G2/M of the cell cycle were selected. The phenotype of treated cells was compared to that of exponentially replicating controls in an attempt to identify any differences that could potentially affect viral replication. Ultrastructural examination of cells treated with compounds to block replication in G1/G0 or in G2/M showed that cytoplasm of treated cells contained abundant paired cisternae. Further studies indicated an apparent correlation between the presence of paired cisternae and intracellular accumulation of HIV-1 virions. Infection studies showed that U937 TK- cells were more permissive for a lymphotropic strain of HIV-1 than for a monocytotropic isolate. Intracytoplasmic p24 antigen levels were significantly higher in U937 TK- cells that had been treated with 300 muM mimosine. This result was thought to be due to induction of cellular differentiation, rather than to a cell cycle related phenomenon. However, accumulation of cells in G2/M following treatment with 1 x 10-8muM colchicine, (and to a lesser extent 75 muM GR39457A), caused a significant enhancement of viral replication which was not dependent on significant changes in the host cell phenotype.