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Low-fading immunofluorescence with propidium iodide contrast compared with immunogold light microscopy in whole cells
Insights
This study introduces a new immunofluorescence method using p-phenylenediamine and propidium iodide for enhanced Herpes simplex virus type 1 (HSV-1) visualization. The technique offers brilliant contrast and minimal fading, improving upon traditional methods for microscopy.
Area of Science:
- Cell Biology
- Virology
- Microscopy Techniques
Background:
- Conventional immunofluorescence (IF) offers excellent labeling but suffers from fading and requires phase-contrast microscopy.
- Silver-enhanced colloidal gold probes allow permanent preparations but are limited by steric hindrance and silver enhancement artifacts.
- Investigating Herpes simplex virus type 1 (HSV-1) morphogenesis requires sensitive and reproducible immunocytochemical methods for light microscopy confirmation and screening.
Purpose of the Study:
- To develop a sensitive and reproducible immunocytochemical light microscopic method for confirming immunofluorescence results.
- To screen cryopreparations for electron microscopic studies of HSV-1 morphogenesis.
- To overcome the limitations of conventional immunofluorescence and silver-enhanced colloidal gold techniques.
Main Methods:
- Utilized p-phenylenediamine as an anti-fading agent.
- Employed propidium iodide for counter-staining.
- Evaluated the method for Herpes simplex virus type 1 (HSV-1) immunogold cryosection electron microscopy screening.
Main Results:
- The developed method produced brilliant fluorescence and contrast.
- Minimal autofluorescence was observed.
- Fading was negligible for at least 5-minute exposures, even with weak antigen presentation.
- Stable fluorescence was achieved upon storage at -20°C.
Conclusions:
- The new immunofluorescence method, using p-phenylenediamine and propidium iodide, is superior to silver-enhanced colloidal gold light microscopy for HSV-1 investigations.
- This technique provides enhanced sensitivity, reproducibility, and stability for immunocytochemical analysis.
- It serves as an effective preliminary screening tool for electron microscopy studies.
Abstract:
Conventional immunofluorescence produces excellent labeling but has drawbacks such as fading and the need for phase-contrast. Silver-enhanced colloidal gold probes allow counterstaining and permit permanent preparations with no fading if mounted correctly, but the most common limits of this technique are steric hindrance and the artifacts produced by silver enhancement. Our goal was to investigate Herpes simplex virus type 1 (HSV-1) morphogenesis by immunogold cryosection electron microscopy. We therefore needed a sensitive and reproducible immunocytochemical light microscopic method to confirm the immunofluorescence results in whole cells and to screen the cryopreparations before the time-consuming electron microscopic studies. We report data showing that the use of p-phenylenediamine to retard fading and propidium iodide to provide counter-staining results in brilliant fluorescence and contrast, minimal autofluorescence, and invisible fading at least for 5 min exposures, even in preparations with weak antigen presentation. Storage at -20 degrees C provides stable fluorescence. This method is superior to silver-enhanced colloidal gold light microscopy in our investigations.