Enzymatic amplification of exogenous and endogenous retroviral sequences from DNA of patients with tropical spastic paraparesis.

Using oligonucleotide primers that hybridize to conserved sequences in the reverse transcriptase (RT) gene, we have amplified by the polymerase chain reaction three sequence variants of HTLV-I from the genomic DNA of five patients with tropical spastic paraparesis (TSP), and a fourth sequence variant from a healthy carrier of HTLV-I. These results unequivocally identify the retrovirus associated with TSP as HTLV-I and suggest that no sequence variant is uniquely responsible for the condition. The same primers served to amplify two novel single-copy endogenous retroviral RT sequences related to the exogenous mammalian leukaemia viruses: and three KpnI (LINE1) family DNA repeats. This strategy, combining the sensitivity of PCR with cross-reactive primers, may be useful in the search for known or novel retroviruses in other diseases of possible retroviral aetiology.