Expression, purification of herpes simplex virus type 1 UL4 protein, and production and characterization of UL4 polyclonal antibody

The herpes simplex virus type 1 (HSV-1) UL4 protein is a late protein encoded by the UL4 gene. To date, the function of this protein is poorly understood. To aid further investigation of the function of this protein, the UL4 gene was cloned into the vector pET28a (+) to express His-tagged UL4 protein in Escherichia coli. The recombinant fusion protein was purified from inclusion body by histidine selected nickel affinity chromatography under denaturing conditions. After refolding, the purified recombinant protein was used to produce anti-UL4 polyclonal antibody. Western blot analysis demonstrated that the polyclonal sera could recognize the purified UL4 protein specifically, and in the immunofluorescence assay, the antibody was able to probe the UL4 protein with a punctate staining in HSV-1 infected cells.