tokens: However , this efficient propagation of the LTR-modified tat mutants was restricted to some lymphoid cell lines that have been transformed with other viruses .
folded_tokens: however , this efficient propagation of the ltr-modified tat mutants was restricted to some lymphoid cell lines that have been transformed with other viruses .
labels: O O O O O O O B-protein_family_or_group B-protein_family_or_group I-protein_family_or_group O O O O B-cell_line I-cell_line I-cell_line O O O O O O B-virus O