Deletion of gene 52 encoding glycoprotein M of equine herpesvirus type 1 strain RacH results in increased immunogenicity

The immunogenicity of equine herpesvirus type 1 (EHV-1) strain RacH was com pared to a RacH virus in which gene 52 encoding glycoprotein M (gM) was int errupted by insertion of LacZ (H Delta gM-Ins) and a RacH with 75% of gene 52 was deleted and replaced by LacZ (H Delta gM-HS). H Delta gM-Ins failed to produce full-length gM, but the carboxy-terminal portion was still expre ssed. No gM expression was detected in H Delta gM-HS-infected cells. Mice w ere immunised once with 1 x 10(3) to 1 x 10(5) plaque-forming units (PFU) o f RacH or mutant viruses and challenged with virulent RacL11 virus 29 days later. A dose-dependence of protection was observed in RacH-immunised mice, and following immunisation with 1 x 10(4) or 1 x 10(3) PFU body weight los ses and increased virus titres in lungs were observed after challenge infec tion, H Delta gM-HS-immunised mice were completely protected even after imm unisation with 1 x 10(3) PFU. Mice immunised with 1 x 10(3) PFU of H Delta gM-Ins but not the higher doses showed signs of disease after challenge inf ection. (C) 2001 Elsevier Science B.V. All rights reserved.