10B. Lecture Flashcards
Morphological changes in cells independently from virus infections
aka. non-specific CPEs
•aging of the cells
•alteration of the pH range of the medium
•alteration of the incubation’s temperature
•toxic components in the inoculum
•bacterial contamination
how are non-specific CPEs differentiated?
- Compare with the uninfected control
- Passage the isolate
- Perform direct demonstration:
- PCR, IHC, ISH
- VN
direct damage of viruses on cells
- toxic effect of adsorption
- virus proteins inhibit cellular translation
- early proteins inhibit cellular nucleic acid transcription and replication
- viral proteins or virions are deposited in the cells
- viral proteins damage the cytoplasmic membrane permeability - osmotic changes
- cytosceleton depolymerisation
- expression of fusion proteins
CPEs are usually investigated how
- Usually investigated by light microscopy (100-400 × magnification)
- some of the CPEs are visible in unstained cells
- staining (HE, Giemsa, etc.) usually gives more detailed information
non-CPE producing viral infections
•the cytopathic character of a virus strain may change due to mutations (i.e. BVDV)
•the CPE is not always connected to the pathogenicity of the virus
-CSF - no CPE but pathogen
-Spumaviruses- obvious CPE but orphan
The appearance of the CPE is influenced by
multiplicity of
infections (MOI)
•the most characteristic CPE is seen by low MOI (<0.1)
CPEs
•CPE may occur independently or jointly •Different viruses may cause similar CPE •CPE may vary according to the host cell → CPE alone is usually not pathognomic → CPE is important character for the identification of the virus
Inclusion body formation
- at the site of assembly of nucleocapsid → virus deposition (in nucleus RNA sometimes too, cytoplasm both RNA and DNA in eosinophils usually)
- seen in stained cells (of cell cultures or organ sections)
- homogenous staining
- surrounded by halo - shrinkage after fixation
negri bodies and guarnieri bodies
•pathognomic IC inclusion bodies
Negri bodies (rabies), Guarnieri bodies (pox)
cell rounding
- one of the most frequent CPE
- cytosceleton depolymerisation
- loss of electrolytes
- unstained: double refraction, detachment, shrinkage
- stained: intensive staining
Syncytium-formation
•caused exclusively by enveloped viruses
•fusion proteins (F) on the surface of the virus
•primarily for viral penetration
•expressed on the cytoplasmic membrane of the cell
•fusion of infected and non-infected cell membranes
→ membrane tunnels → intracellular spread
→ hidden from the antibodies
•giant cells with many nuclei: polykaryocytes, syncytia
•in tissue sections multinucleated giant cells may be seen
→usually lymphatic cells
→results of impaired cellular division
Lumpy cell nucleus
- chromatin conglomeration, rearrangement
- changed refraction (parvo)
- nucleus lumpy disintegration
Cell vacuolisation
•vacuoles are formed in the cells in cytoplasm or nucleus
hemadsorption
•viral hemagglutinin is expressed on the surface of the
infected cells
•RBCs are added into the culturing medium, and after 30
minutes incubation unbound RBCs are washed away
•infected cells are capturing RBCs
diffuse vs. local/focal CPEs
Diffuse: all around in the cell culture
Local / focal: plaques
•certain viruses more frequently appear in plaques
•in lower MOI more frequently plaques are formed
•syncytia are seen as plaques
