Detection and cellular localization of enterovirus RNA sequences in spinal cord of patients with ALS

Objective: To investigate the possible association of persistent enterovirus (EV) infection with the development of ALS. Background: Although ALS is a clinically well-defined motor neuron disease, little is known about the etiology and pathogenesis of the sporadic cases. Among the different causes that have been hypothesized, conflicting results have been reported about the possible role of persistent enteroviral infection. Methods: Reverse transcriptase-PCR (RT-PCR) and direct RT in situ PCR (RT-IS-PCR) were performed in formaldehyde-fixed spinal cord samples of 17 patients with confirmed ALS and 29 control subjects with no history of motor neuron disease. When obtained, PCR products were sequenced subsequently. Results: Using direct RT-IS-PCR, EV nucleic acid sequences were detected in 15 (88.3%) of 17 patients with ALS compared to 1 (3.4%) of 29 control subjects. PCR products were located in neuronal cell bodies of the anterior horns of the spinal cord. The RT-PCR products obtained in 13 of the 17 patients with ALS showed between 94% and 86% homology with echovirus 7 sequences. Conclusion: The 88.3% rate of detection of enterovirus (EV) nucleic acids in the neuronal cell bodies within the gray matter of the spinal cord of patients with ALS strongly suggests association between persistent EV RNA and ALS. Further work is required to confirm that the persisting EV sequences we detected are somehow involved in the development of ALS.