Development of T-cell lines expressing functional HIV-1 envelope glycoproteins for evaluation of immune responses in HIV-infected individuals

The human T-lymphoid cell line, CEM, was transfected with gp160 cDNA of human immunodeficiency virus type I (HIV-1)(pm₂₁₃). Three clones expressing the envelope glycoproteins (env), designated CEM-213env1, -env4, and -env7, were isolated. These clones expressed high levels of surface gp41 and gp120, as demonstrated by flow cytometry with anti-HIV env monoclonal antibodies. Processing and function of env was shown by induction of syncytia with CD4-expressing HeLa cells and by immunoblot analysis. The env expression resulted in specific down-regulation of surface CD4 levels, supporting the role of HIV env, in CD4 modulation. Furthermore, serum samples from nine of nine HIV-1-infected individuals bound specifically to the env-expressing transfectants, substantiating the presence of conserved antigenic determinants. These sera also mediated antibody-dependent cellular cytotoxicity (ADCC) of the env-expressing cell lines. The env-expressing cell lines provide a relevant, safe, and practical model for qualitative and quantitative analysis of humoral and cellular immune responses and their role in HIV-1 pathogenesis and therapy.