Confirmation of low-titer, herpes simplex virus-positive specimen results by the enzyme-linked virus-inducible system (ELVIS) using PCR and repeat testing

The ELVIS HSV Id test kit (an enzyme-linked virus-inducible system) (Diagno stic Hybrids, Inc.) uses genetically engineered BHK cells to produce a dete ctable enzyme, beta-galactosidase, upon infection with either herpes simple x virus (HSV) type 1 (HSV-1) or HSV-2. Twenty six ELVIS-positive clinical s pecimens were selected for study by PCR and with monoclonal antibodies beca use they were originally low-titer HSV-positive specimens by ELVIS but HSV antibody nonreactive upon follow-up staining of the ELVIS monolayer, Twenty -one of 26 specimens were frozen, thawed, and retested with ELVIS without r emoving the cellular debris from the specimen; 18 were ELVIS positive and 3 were ELVIS negative on retesting. A typing result was provided upon retest ing for 14 of 18 ELVIS-positive specimens (11 were HSV-I and 3 were HSV-2) with HSV-specific monoclonal antibodies; no antibody signal was observed fo r 14 of 18 ELVIS-positive specimens. Sixteen of 26 specimens were subjected to blinded PCR analysis with two different primer sets, including all thos e that were repeat tested with ELVIS without success and those that had ins ufficient quantity for repeat testing, All 16 specimens analyzed were PCR p ositive with primer set 1; 15 of 16 were also positive with primer set 2, w ith the HSV type identified for all specimens (7 were HSV-1 and 8 were HSV- 2), These results indicate that the original ELVIS result with these low-ti ter specimens was correct and further confirm the sensitivity and specifici ty of ELVIS HSV Id as a rapid, cell culture-based kit for the detection of HSV.