Peripheral blood lymphocytes (PBL) and CEM CD4+T-cell line can be infected by herpes simplex virus-1 (HSV-1). CEM cells were characterized as a cellular model to study interactions occurring between HSV-1 and HIV-1. Virtually all cells were persistently infected by HSV-1 (CEMHSV) and expressed the latency associated transcripts, whereas only a fraction tested positive for HSV-antigens. CD4 and CXCR-4 expression and function were not affected in CEMHSVcells and no significant increase of deoxyribonucleotide pools was noticed. Superinfection of CEMHSVcells with HIV-1 led to a cell line chronically infected by both viruses (CEMHIV/HSV). Evidence was also obtained that this cell line can produce HIV-1 pseudotyped by HSV-1 envelope. These results may have important implications for a better under-standing of AIDS pathogenesis.