Analyses on mechanisms of HIV-1 infection using irradiation of heavy ion beam

Abstract

In order to identify a new cellular factor required for human immunodeficiency virus type I (HIV-1) infection, we established a new indicator cell line to detect HIV-1 infection easily and real-time. Using irradiation with heavy ion beams, we tried to mutagenize human cells to isolate mutant cells that become resistant to HIV-1 infection. Human glioma-derived NP-2 cells transduced with HIV-1 receptor CD4 and coreceptor CCR5 were further transduced with the GFP gene that will be expressed under the control of HIV-1 long terminal repeat (LTR). We established N4R5/GFP cells that showed a low background of GFP expression before infection but became GFP-positive after HIV-1 infection. N4R5/GFP cells may be used as a model of cells latently infected with HIV-1. We examined the effects of irradiation with heavy ion, ultraviolet (UV-C), or X-ray, or treatment with TNF-α,DNA damaging agents or a histone deacetylase inhibitor (trichostatin A) on the appearance of GFP-positive N4R5/GFP cells.¹²C⁵⁺ and ⁴He²⁺ ions, UV-C, 4NQO, MNNG, cisplatin, and trichostatin A induced GFP expression in N4R5/GFP cells, although their induction efficiencies varied markedly. X-ray and 5-azaC showed hardly any effects. These results suggest that heavy ion beam may promote the reactivation of HIV-1. We next tried to isolate cells mutants in HIV-1 susceptibility. Cells irradiated with heavy ions were seeded to make their colonies and a dose (D10) that decreases the colony forming efficiency to 10% was determined. D10s for ⁴He²⁺ and ¹²C⁵⁺ irradiation were 2.6 and 0.9 Gy, respectively. We examined HIV-1 susceptibilities of cells derived from irradiated colonies. Although many colonial cell lines formed GFP-positive syncytia after HIV-1 infection, some lines formed GFP-negative syncytia, suggesting that heavy ion beams had affected transduced or cellular gene.