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Persistence of human herpesvirus 7 in normal tissues detected by expression of a structural antigen
W Kempf1, V Adams, P Mirandola
1Department of Dermatology, University Hospital, Zurich, Switzerland.
Abstract:
Human herpesvirus 7 (HHV-7) infection in histologically normal human tissues was investigated by immunohistochemical detection of the 85-kDa tegument phosphoprotein (pp85) encoded by the U14 gene. So far, two cell types were recognized as sites of HHV-7 infection in vivo: CD4+ T lymphocytes, believed to be the site of latent infection, and epithelial cells of salivary glands, the site of productive infection and viral shedding. Unexpectedly, cells expressing the HHV-7 structural antigen were detectable in lungs, skin, and mammary glands. Morphologically and phenotypically, they were distinct from lymphocytes. Liver, kidney, and tonsils were positive, although the number of HHV-7-positive cells was low. Large intestine, spleen, and brain were negative. Different from the current notion of the state of HHV-7 in humans, the results show that a variety of tissues harbor cells at a late stage of infection and suggest that HHV-7 causes a persistent rather than a true latent infection.
Insights
Human herpesvirus 7 (HHV-7) infection is not limited to T lymphocytes and salivary glands. This study reveals HHV-7 in various tissues, suggesting persistent infection rather than true latency.
Area of Science:
- Virology
- Immunology
- Pathology
Background:
- Human herpesvirus 7 (HHV-7) is known to infect CD4+ T lymphocytes (latent) and salivary gland epithelial cells (productive).
- The precise tissue distribution and nature of HHV-7 infection in humans remain incompletely understood.
Purpose of the Study:
- To investigate the presence and characteristics of HHV-7 infection in histologically normal human tissues.
- To determine if HHV-7 infection is limited to previously identified cell types and states.
Main Methods:
- Immunohistochemical detection of the HHV-7 U14 gene-encoded 85-kDa tegument phosphoprotein (pp85).
- Examination of various human tissues including lungs, skin, mammary glands, liver, kidney, tonsils, large intestine, spleen, and brain.
Main Results:
- HHV-7 structural antigen was unexpectedly detected in cells within lungs, skin, and mammary glands, distinct from lymphocytes.
- Positive cells were also found in liver, kidney, and tonsils, albeit in lower numbers.
- Large intestine, spleen, and brain tissues tested negative for HHV-7 antigen.
Conclusions:
- HHV-7 infects a broader range of human tissues than previously recognized.
- The findings challenge the concept of HHV-7 latency, indicating a persistent infection state in various tissues.