BK Virus by IHC

BK Virus by IHC (Immunohistochemistry) – Pathology Content

BK Virus Nephropathy is most commonly seen in immunocompromised patients, especially renal transplant recipients. Immunohistochemistry (IHC) plays an important role in confirming viral infection in tissue biopsies.

Key IHC Marker

• SV40 Large T Antigen is the standard surrogate marker used for BK virus detection.
• Positive staining appears as strong nuclear positivity in infected tubular epithelial cells.

Histopathological Features

• Enlarged tubular epithelial cells
• Basophilic intranuclear viral inclusions
• Tubulointerstitial inflammation
• Tubular injury and atrophy
• “Decoy cells” may be seen in urine cytology.

Typical IHC Interpretation

Positive for SV40 (nuclear staining):

• Supports BK polyomavirus infection/nephropathy
• Common in renal allograft biopsies

Negative SV40 staining:

• Does not support active BK viral replication
• Correlate with PCR and clinical findings

Sample Reporting Format

IHC: SV40 immunostain shows strong nuclear positivity in renal tubular epithelial cells.
Impression: Findings are consistent with BK polyomavirus nephropathy.

Clinical Importance

BK virus nephropathy can mimic acute rejection in transplanted kidneys, making IHC essential for differentiation and treatment planning.