Characterization of monoclonal antibodies raised against the latent nuclear antigen of human herpesvirus 8

Human herpesvirus 8 (HHV-8; also designated Kaposi's sarcoma-associated her pesvirus) is the likely etiological agent of Kaposi's sarcoma (KS). HHV-8 e ncodes a latent nuclear antigen (LNA) which is the product of the viral gen e orf 73. LNA is recognized by most infected patient sera and is the basis of current immunofluorescence assays used in epidemiological studies of HHV -8 infection. Here we describe the characterization of four monoclonal anti bodies raised to the C-terminal third of LNA-glutathione S-transferase fusi on proteins. These monoclonal antibodies recognized discrete linear epitope s within the C terminus and repetitive region of LNA, detected antigen in p rimary effusion lymphoma (PEL) cells, and precipitated a 220- to 230-kDa pr otein doublet corresponding to LNA from HHV-8-infected PEL cell lines. In s itu immunocytochemistry of KS lesions with these antibodies show that LNA i s extensively expressed in KS spindle cells.