Immunoreactivity for latent membrane protein 1 of Epstein-Barr virus in nevi and melanomas is not related to the viral infection

Epstein-Barr virus (EBV) is a human herpes virus with oncogenic potential, associated with several malignancies. The EBV-encoded latent membrane prote in 1 (LMP1) is one of nine proteins regularly expressed in virally infected and immortalised B lymphocytes. We now document the consistent immunoreact ivity for LMP1 in 90% of 65 nevi and melanomas, using the monoclonal antibo dy cocktail CS1-4. The immunocytochemical findings, however, were not confi rmed using reverse-transcription polymerase chain reaction (RT-PCR) experim ents, which failed to demonstrate any actual expression of LMP1 mRNA. In si tu hybridisation for EBV-encoded RNAs (EBERs 1 and 2) and PCR amplification of EBV genomic sequences also failed to document any viral infection. Seve ral normal and neoplastic human tissues have also been immunostained for LM P1, without any positive staining, with the exception of a minor percentage of skin melanocytes and of normal blasts of the myeloid and erythroid line ages. We conclude that the vast majority of nevi and melanomas express a st ill uncharacterised molecule, cross-reacting with anti-LMP1 (CS1-4) antibod ies, which may be considered a consistent marker of melanocytic proliferati ons. The immunoreactivity of normal and neoplastic human tissues for the an ti-LMP1 reagent should not be taken as evidence of EBV infection.