An antigen encoded by the latency-associated transcript in neuronal cell cultures latently infected with herpes simplex virus type 1.

During latent infection of neurons with herpes simplex virus type 1, viral transcription is restricted to the latency-associated transcripts (LATs). These RNAs contain open reading frames, but detection of a protein encoded by the LATs has not been reported. We used immunocytochemical techniques to demonstrate that an antiserum directed against a bacterially expressed fusion protein containing part of a LAT-encoded polypeptide recognized an antigen present in primary neurons latently infected in vitro. This antigen (called LAA, for latency-associated antigen) was not detected in mock-infected neurons, in productively infected Vero cells, or in neurons latently infected with a mutant virus carrying a deletion in the LAT gene. By Western immunoblot analysis, we demonstrated the presence of a protein with an apparent molecular mass of 80 kDa recognized by the anti-LAA antiserum in latently infected neurons.