New insights into the viral theory of amyotrophic lateral sclerosis: study on the possible role of Kaposi's sarcoma-associated virus/human herpesvirus 8

In the last few years, three new herpesviruses, HHV-6, -7 and -8, have been discovered, which share interesting biological characteristics for a possible role in the development of both neurological and lymphoproliferative diseases. In particular HHV-8, besides being strongly associated with Kaposi's sarcoma, is related with several lymphoproliferative diseases. More recently, specific viral sequences belonging to HHV-8 have been detected in autoptic brain specimens from multiple sclerosis patients and controls, suggesting that, similarly to HHV-6, this novel herpesvirus is strongly neurotropic. HHV-8 is an unusual herpesvirus in that it is able to produce homologues of several human gene products, resulting in alterations in cell cycle, in apoptosis and cell-mediated immune responses. To verify a possible relationship between HHV-8 and the development of amyotrophic lateral sclerosis (ALS), we investigated the presence of signs of HHV-8 infection, by both nested polymerase chain reaction (nPCR) and indirect immune fluorescence analysis in ALS patients. Both PCR and serological data did not suggest a clear role of this virus in originating ALS. Nevertheless, new insights into the mechanisms by which viruses may interact with the host cell genome and with the human immune system make the viral hypothesis of ALS still worthy of further studies.