Replication-Competent Herpes simplex Virus Type 1 Mutant Expressing an Autofluorescent Glycoprotein H Fusion Protein

Abstract

The heterocomplex of glycoproteins H (gH) and L (gL) of herpes simplex virus type 1 (HSV-1) is essential for viral infectivity and is involved in viral penetration, cell-to-cell spread, and syncytium formation. We constructed an HSV-1 mutant expressing a gH-EGFP (enhanced green fluorescent protein) fusion protein under the control of the gH true late promoter. The EGFP coding sequence was cloned after the gH signal peptide into the HSV-1 genome. Superinfection of transfected, gH-nontranscomplementing cells with gH-negative HSV-1 resulted in a replication-competent recombinant virus. Cells infected with the recombinant virus exhibited strong and stable EGFP-specific fluorescence late in infection, and autofluorescence was detected in purified virions. The recombinant genotype of the mutant was confirmed by PCR. The 140-kD gH-EGFP fusion protein showed an N-linked glycosylation pattern similar to gH-1, was recognized by the conformation-dependent gH-specific monoclonal antibodies 52S and LP11 and formed a heterocomplex with gL which was transported to the cell surface and integrated into the viral envelope. Infectivity of the gH-EGFP mutant was neutralized by antibodies 52S and LP11. To our knowledge, this is the first replication-competent HSV-1 mutant expressing an autofluorescent essential glycoprotein which will be a versatile tool for studies of penetration, late gene expression, transport and tissue spread.