Lab Diagnostic Testing: Herpes Simplex Virus

The detection of Herpes Simplex (HSV) from ocular specimens is essential for prompt and accurate therapy. HSV can be detected from ocular samples with cell culture, ELVIS™ (Enzyme Linked Viral Induced System) and PCR.

In our laboratory, all clinical ocular samples suspected of possible HSV infection are tested with standard cell culture, ELVIS™, and PCR. We feel that processing all specimens with this battery of tests provides the most expedited results especially when the results can be delayed due to off-hour collection, weekends, and holidays.

Specimen Collection
Cell Culture
ELVIS™
PCR

Specimen Collection
Specimens are directly collected by vigorously swiping the exposed conjunctiva with a plastic soft-tipped applicator. Cornea samples using soft-tipped applicators and spatulas can also be obtained to maximize the yield of viable HSV and antigen. Topical anesthetic can be applied to the conjunctiva and should be applied to the cornea. Collected samples are placed in 2.0 ml of viral transport medium. We have had great success with Bartels ChlamTrans™ chlamydial transport medium and recommend its use. Viral culturettes can also be used for transportation to the laboratory and these can be transferred to the viral medium. All laboratory testing can be processed from the 2.0 ml of chlamydial transport medium. HSV can be fastidious and should be transported to the laboratory without unnecessary delay.

Transport medium
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Cell Culture
The "gold" standard for HSV laboratory testing is cell culture. Collected samples are layered on a monolayer of cells in test tubes. If present, HSV will present as cytopathic effect of rounded cells. We use A549 cells as the cell-line for testing HSV. This is a human carcinoma continuous cell-line. When samples are positive for HSV, cytopathic effect is generally present within one to three days. It is rare, but sometimes one to two weeks is necessary to isolate HSV in cell culture. Cell culture will confirm an HSV diagnosis but it may not provide timely results for immediate patient care. All virology laboratories can offer cell culture isolation for HSV.

HSV cell culture CPE
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ELVIS™
ELVIS™ (Enzyme Linked Viral Induced System) is another cell culture test but the results are ready in ONE day. Cells infected with HSV commence a cascade of reactions that results in the accumulation of beta-galactosidase in the cells. Viral samples are layered on the specially engineered cell line in a shell vial and centrifuged. The vial is incubated for one day (overnight), fixed, and stained with a substrate that reacts with the beta-galactosidase. The reactions result in a blue-color change in the cells that are observed with an inverted microscope. ELVIS™ testing may also be limited in its availability. We highly recommend ELVIS™ testing for diagnosing ocular HSV infection.

ELVIS™ (HSV shell vial culture)
(Click on image to enlarge)

PCR
PCR is performed for HSV (1 or 2) on specimens collected by soft-tipped applicators, metal spatulas, and jeweler's forceps, and placed in 2.0ml of chlamydia transport medium. Intraocular fluid or vitrectomy specimen can be supplied directly or increased to a volume of 0.45 ml with chlamydia transport medium. 0.45 ml of the medium is supplied for PCR testing.