COMPARISION OF DIRECT FLOURESCENT ANTIBODY (DFA) STAINS FOR THE DETECTION OF HERPES SIMPLEX VIRUS 1 & 2 (HSV 1/2) AND VARICELLA-ZOSTER VIRUS (VZV) IN MRC5 AND H&V-MIXTM SHELL VIAL CULTURES

Retrospectively we evaluated 75 specimens (50 HSV 1/2, 25 VZV) collected in M4 viral transport (Remel, Lenexa, KS) for the presence of Herpes Simplex Virus 1 & 2 and Varicella- zoster Virus. Specimens were previously analyzed using conventional cell culture and/or shell vial cultures (Diagnostics Hybrids [DH], Athens, Ohio). Of the 50 HSV specimens used for the study 20 proved HSV1-positive, 20 proved HSV2-positive and 30 were negative for both HSV1 and 2. Similarly, of the 25 VZV specimens 20 proved VZV-positive and 5 were VZV-negative. In the present study, two shell vial culture (SV) systems were used: MRC5 and H&V Mix^TM Mixed cells (DH, Athens, Ohio). After inoculation and overnight incubation, HSV SVs were stained using DH D³ DFA Herpes Simplex Virus Identification and Typing Kit (D³- HSV) or Trinity Biotech (Jamestown, NY) Microtrak® HSV1/HSV2 Culture Identification/Typing Test (MT- HSV). After inoculation and 2 day incubation VZV SVs were stained using DH D³DFA Varicella-zoster Virus Identification Kit (D³-VZV) or Light Diagnostics (Millipore, Temecula, CA) Varicella-zoster Direct Immunoflourescence Assay (LD-VZV). Percentage of overall agreement with reference assays appears in the table below:

HSV results for all systems tested were comparable. The counterstained negative background cells observed with D³-HSV stained shell vials were more readily interpretable when compared with MT-HSV. Superior VZV results were noted in both the LD-VZV/MRC5 and LD-VZV/H&V test systems. Review of discrepant VZV results demonstrated when the specimen was positive, limited reactive cells were present in the SV. Additionally, VZV-positive H&V SVs typically demonstrated more prominent staining with larger foci of infected cells. Based on the cost of our current HSV stain (MT-HSV) and VZV stain (LD-VZV), D³-HSV and D³-VZV reagent price would increase our costs by 30% and 70% respectively if used in accord with DH product insert specifications for stain volume. The test systems will be challenged further to determine endpoint stain efficacy and shell vial efficiency using serially diluted HSV 1/2 and VZV strains.