Intracellular localization and epitope mapping of feline herpesvirus type 1 glycoproteins

Monoclonal antibodies (MoAbs) were used to characterize feline herpesvirus type 1 (FHV-1) glycoproteins (gp). Intracellular localization and transport of these proteins as revealed by a sequential indirect immunofluorescence assay (IFA) on fixed infected cells showed slight differences between FHV-1 gp143/108 and gp113. Antibodies against gp143/108 first showed membrane fluorescence at 4 hrs post-infection (PI) followed by a pronounced perinuclear and cytoplasmic staining from 8 hrs PI onwards. Those reacting with gp113 showed the same pattern but fluorescence did not appear until 8 hrs PI. In contrast, MoAbs against gp60 first showed para- and perinuclear staining at 12 hrs PI which became intranuclear at 16 hrs PI, followed by intracytoplasmic staining at 20 hrs PI. Sequential IFA of unfixed infected cells revealed that the three glycoproteins were expressed on the cell surface membrane as well. Topographical mapping of the functional epitopes of gp113 by ELISA additivity test indicated the presence of 2 antigenic domains--a neutralizing domain consisting of 3 overlapping epitopes and a non-neutralizing domain. On the other hand, gp143/108 contained only one antigenic site consisting of 5 similar or overlapping epitopes, one of which seemed to be a conserved region recognized by all MoAbs reacting to this protein.