Detection of reverse transcriptase activity in the serum of patients with motor neurone disease

The recognition that both human and murine retroviruses can cause motor neu rone disease-like syndromes has raised the possibility that a retrovirus ma y be involved in the aetiology of motor neurone disease. This possibility w as explored by looking for evidence of reverse transcriptase in the serum o f motor neurone disease patients. Sera from 56 patients with motor neurone disease and 58 controls were tested by the product-enhanced reverse transcr iptase assay, a technique that is approximately a million fold more sensiti ve than conventional reverse transcriptase assays and capable of detecting very low numbers of retroviral particles. Cell-free reverse transcriptase a ctivity was detected in the serum of 33 of the 56 motor neurone disease pat ients (59%) but in only 3 of the controls (P < 0.00001). The reverse transc riptase activity was detectable in the presence of a large excess of an eff ective inhibitor of human cellular DNA polymerases and was therefore tentat ively considered to be compatible with a retroviral origin. The reverse tra nscriptase activity, however, was not found to be due to the presence of kn own human exogenous retroviruses including HIV-1, HIV-2, HTLV-I, HTLV-II, H RV-5 or human foamy virus, as assessed by PCR-based assays. Further investi gations will be required to determine the source of the reverse transcripta se activity observed in these motor neurone disease patient sera. J. Med. V irol. 61:527-532, 2000. (C) 2000 Wiley-Liss.