Detection of Herpes Simplex Virus 1,2: Comparison between In Situ Hybridization and Immunohistochemistry Methodologies.
Francis J Walsh, Brooke E McCann, Karen L Grogg. Mayo Clinic, Rochester, MN
Background: Clinically, Herpes Simplex Virus 1,2 (HSV) testing is important to distinguish it from other types of skin lesions, as well as to identify HSV in infected organs when the virus disseminates to other parts of the body. In our practice, both the Immunohistochemistry (IHC) and the In Situ Hybridization (ISH) laboratories perform testing for HSV 1, 2 on tissue sections. In order to streamline processes between the labs and eliminate redundancy, the 2 test methods were compared.
Design: Testing was performed on formalin fixed-paraffin embedded (FFPE) tissue sections. A total of 58 cases were collected on which HSV testing either by ISH or by IHC had been previously performed. After heat induced epitope retrieval in EDTA pH 8.0, IHC testing was performed on a Dako Autostainer using a rabbit polyclonal antibody (Cell Marque), dilution 1:200, with Dako Advance detection and DAB chromagen. The ISH testing was performed using a manual procedure and a biotin labeled probe (Enzo Life Sciences Inc.) followed by streptavidin alkaline phosphatase detection (Vector) with NBT/BCIP chromagen (Roche). Completed slides were reviewed by two technologists and a pathologist.
Results: Of the 58 cases tested, 42 were positive by IHC showing strong staining of viral and cytoplasmic inclusions in infected cells. 40 of these cases were positive for HSV by ISH, showing primarily nuclear staining in infected cells. 2 additional cases showed equivocal positivity by IHC with staining in necrotic debris only, and were negative by ISH. Of the 4 cases that were positive or equivocal for HSV by IHC but negative by ISH, 3 were skin biopsies of vesicular lesions showing morphologic features suggestive of herpetic infection on H&E levels, and thus were considered a true positive result. The fourth case was a lung biopsy showing a lymphohistiocytic infiltrate with necrosis in an immunosuppressed patient. A nasal swab from this patient was positive for HSV1 by PCR studies, supporting the conclusion that the IHC staining in necrotic debris represented true positivity. Overall, our ISH method detected HSV in 91% of the cases that were positive by IHC.
Conclusions: For the detection of HSV 1,2 in FFPE specimens, our ISH and IHC methods give comparable results, with IHC showing slightly better sensitivity than ISH, particularly in necrotic tissues.
Monday, February 28, 2011 1:00 PM
Poster Session II # 254, Monday Afternoon