Viral Morphology Changes in Cells

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Questions and Answers

What is the primary limitation of the Tzanck smear test in diagnosing HSV or VZV?

High cost and labor-intensive process

Inability to distinguish between HSV and VZV

Poor sensitivity and specificity (correct)

Lack of specificity due to overlap with other diseases

What type of analysis can be used to detect the presence of specific viral proteins in tissue sections?

Electron Microscopy

Immunohistochemistry (correct)

Polymerase Chain Reaction

Immunofluorescence

What is the term for the characteristic changes in cellular morphology caused by viral infections?

Viral inclusion bodies

Necrosis

Cytopathic effect (correct)

Apoptosis

What is the purpose of using tagged antibodies in immunohistochemistry?

To detect specific viral proteins Signup and view all the answers

What type of viral diagnostic method involves the amplification of viral nucleic acid sequences?

Polymerase Chain Reaction (PCR) Signup and view all the answers

What is the term for the accumulation of newly assembled virus particles in the cytoplasm or nucleus of infected cells?

Viral inclusion bodies Signup and view all the answers

What is the primary purpose of the TCID50 assay in viral quantification?

To estimate the amount of infectious virus present in a suspension Signup and view all the answers

What is the characteristic feature of owl's eye cells in CMV infection?

Nuclear and cytoplasmic inclusions Signup and view all the answers

What is the primary method used to detect viral infection in the TCID50 assay?

Cytopathic effect Signup and view all the answers

What is the purpose of serial dilution in the TCID50 assay?

To determine the infectious titer of a virus suspension Signup and view all the answers

What is the characteristic feature of Negri bodies in rabies virus infection?

Found in the cytoplasm of nerve cells Signup and view all the answers

What is the primary application of histopathology and cytopathology in viral diagnosis?

To analyze cellular morphology for viral infection Signup and view all the answers

What is a limitation of conventional viral culture?

It requires significant technical expertise Signup and view all the answers

What is the purpose of a phenol red indicator in cell culture medium?

To produce an obvious color change when the pH is out of range Signup and view all the answers

What type of effect can viruses have on cultured cells?

Cytopathic effect Signup and view all the answers

What is a benefit of viral culture compared to other diagnostic techniques?

It can be used for a wide range of specimen types Signup and view all the answers

What is the purpose of a shell vial assay?

To detect viral antigens Signup and view all the answers

What is the unit of measurement for quantifying viral growth?

Plaque-forming units (PFU) Signup and view all the answers

Study Notes

Viral Diagnosis

Pap smear can detect HPV, showing koilocytic atypia
Parvovirus B19 can be detected by enlarged nuclei of erythroid precursors in a peripheral blood smear
HSV can be detected by Tzanck smear of a lesion scraping, showing multinucleated giant cells

Morphologic Changes

Some viruses produce characteristic changes to cellular morphology
Changes can be highly specific for viruses, while others may overlap with other diseases or infections
Confirm etiology with a more specific test

Viral Inclusions

Newly assembled virus particles can accumulate in the cytoplasm or nucleus
Aggregates of viruses and viral proteins can be seen as viral inclusion bodies

Immunohistochemistry (IHC)

Tagged antibodies specific to certain viral proteins can detect specific viruses in tissue sections

Viral Quantification

TCID50 assay estimates the amount of infectious virus in a suspension
Serial dilutions of virus are used to infect cell monolayers
The dilution at which there is no virus in 50% of replicates is the TCID50

Histopathology and Cytopathology

Techniques used to detect viral infection by examining stained cells (cytology) or tissue sections (histology)
Detects viral infection by characteristic inclusions or cell morphology

Histologic Identification of Viruses

CMV: owl's eye cells with nuclear and cytoplasmic inclusions
Parvovirus B19: enlarged ground glass nuclei in fetal liver
Adenovirus: smudge cells in lung tissue
Rabies virus: Negri bodies in the cytoplasm of nerve cells
HSV: multinucleation, margination, and molding
JC virus: ground-glass intranuclear appearance in oligodendrocytes

Culture and Tissue-Based Diagnostic Techniques

Conventional viral culture can identify live viruses in various specimen types
Cell lines are used to grow and amplify viruses in the laboratory
Procedure involves inoculating the specimen onto a cellular monolayer
Factors in cell culture medium include buffered medium, salts, amino acids, glucose, and vitamins

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Description

Identify the characteristic morphologic changes to cellular morphology caused by different viruses, including HPV, Parvovirus B19, HSV, and HTLV. Recognize the distinct features of each virus in blood smears and other diagnostic tests.