Characterization of the assembly and processing of infectious laryngotracheitis virus glycoprotein B

Infectious laryngotracheitis virus (ILTV) is an alpha-herpesvirus that causes severe upper respiratory infections in chickens. Although ten putative ILTV glycoprotein genes have been identified by sequence analysis, no ILTV glycoprotein has been extensively characterized. In order to delineate the synthesis and processing pathway of ILTV glycoprotein B (gB), rabbit polyclonal antibodies were raised against a Cro-gB-beta-galactosidase fusion protein. Through immunoprecipitation analysis of ILTV-infected chicken embryo liver cells it was determined that ILTV gB is initially synthesized as a 110 kDa monomeric precursor protein which rapidly assembles into homodimers composed of 100 kDa subunits. The dimer form of ILTV gB is rapidly cleaved to form two disulphide-linked species of 58 kDa. The apparent reduction in mass (from 110 to 100 kDa) of the mature form of gB during processing in the Golgi apparatus appears to be a common feature of avian herpesvirus gB proteins.