Unintegrated two-long terminal repeat circular human T lymphotropic virus DNA accumulation during chronic HTLV infection.

Accumulation of unintegrated human T lymphotropic virus (HTLV) DNA was analyzed in long-term T cell lines infected with HTLV type I (HTLV-I) or type II (HTLV-II). By using a polymerase chain reaction-based assay, amplified products of expected size were obtained in all of the HTLV-I-infected (n = 7) and HTLV-II-infected (n = 8) cell lines. The signal intensities of the hybridizing band varied greatly among the cell lines and did not correlate with HTLV p24gag antigen production. Further analysis of HTLV-I-infected clones demonstrated considerable variability in the unintegrated DNA accumulation, suggesting that either the epigenetic status of the host cell or some environmental factor determines the occurrence of unintegrated DNA. The presence of lower levels of unintegrated DNA in most of the HTLV-infected, long-term cell lines presumably results in persistent noncytopathic infection.