tokens: To gain a better understanding of the impact of long terminal repeat ( LTR ) sequence diversity on LTR -directed gene expression in cells of the central nervous system ( CNS ) and immune system , we amplified and cloned LTRs from proviral DNA in HIV-1 -infected peripheral blood .
folded_tokens: to gain a better understanding of the impact of long terminal repeat ( ltr ) sequence diversity on ltr -directed gene expression in cells of the central nervous system ( cns ) and immune system , we amplified and cloned ltrs from proviral dna in hiv-1 -infected peripheral blood .
labels: O O O O O O O O O B-DNA_domain_or_region I-DNA_domain_or_region I-DNA_domain_or_region O B-DNA_domain_or_region O O O O B-DNA_domain_or_region O O O O O O O B-body_part I-body_part I-body_part O B-body_part O O B-body_part I-body_part O O O O O B-DNA_domain_or_region O B-DNA_family_or_group I-DNA_family_or_group O B-virus O O O O