Rapid detection of HSV with an enzyme-linked virus inducible system ™ (ELVIS ™) employing a genetically modified cell line

Abstract

Background: Infections with herpes simplex viruses (HSV) are common and may cause severe disease in immunocompromised hosts and in neonates. Isolation of infectious HSV in tissue culture is the most sensitive method of detection, but is not the most rapid. Recently, however, an Enzyme-Linked Virus Inducible System ™ (ELVIS ™) for rapid detection of HSV in culture has been developed. The system employs genetically engineered baby hamster kidney (BHK) cells (ELVIS ™ cells) whose DNA bears and HSV inducible promoter gene chimerically linked to an E. coli LacZ “reporter” gene. Induction of the promoter by HSV leads to the production of LacZ product, β-galactosidase, which is readily detected histochemically. Objective: To evaluate these ELVIS ™ cells, as a test for HSV, in comparison with HSV detection in MRC-5 cells in shell vial cultures confirmed by staining with fluorescent antibodies. Study design: Over a period of one month, 167 specimens submitted to the laboratory for detection of HSV were evaluated. Specimens were inoculated onto MRC-5 cells growing on glass coverslips in each of two shell vials and into two wells of a 24-well cluster plate containing ELVIS ™ cells. MRC-5 shell vial cultures were observed daily for cpe for up to 7 days. With the appearance of cpe, the coverslips were fixed and the cells were typed for HSV-1 and HSV-2 with monoclonal antibodies. Specimens inoculated onto ELVIS ™ cells were incubated for 16–24 h, then substrate was added to stain for β-galactosidase. ELVIS ™ cells, induced by HSV infection to express β-galactosidase, stained blue upon reaction with substrate. Results: Of 167 specimens inoculated onto MRC-5 cells, 13 were excluded because of contamination or toxicity. Among the remaining 154 specimens, 24 were positive for HSV in the MRC-5 shell vials. Of 166 specimens inoculated into the ELVIS ™ cell, all were completed within 24 h. Twenty-three (23) of the 24 shell-vial-positive cultures also were positive on the ELVIS ™ cells. All 23 specimens detected in the ELVIS ™ cells were positive within 24 h, whereas only nine were positive within 24 hours in MRC-5 shell vial cultures. The remaining 15 became positive after 24 h. Specimens positive for viruses other than HSV-1 or HSV-2 were not positive on the ELVIS ™ cells. Conclusions: The ELVIS ™ assay for HSV is simple to perform, is rapid, sensitive, and specific. The assay detects both HSV-1 and HSV-2. No antibodies are required unless typing, which can be done on the ELVIS ™ cells, is necessary.