Biomedical Engineering Reference
In-Depth Information
2.
Indirect Examination
Cell culture: cytopathic effect, hemadsorption, confirmation by neutralization,
interference, immunofluorescence, etc.
●
Eggs pocks on chorioallantoic membrane (CAM): hemagglutination, inclusion
bodies
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Animal disease or death confirmation by neutralization
●
3.
Serology
Serology is about detection of rising titers of antibody between acute and
convalescent stages of infection, or the detection of IgM in primary infection.
Diagnostic Methods for Detection of Viral Infection
Classical Techniques
Newer Techniques
1.
Complement fixation tests (CFT)
1.
Radioimmunoassay (RIA)
2.
Hemagglutination inhibition tests
2.
Enzyme-linked immunosorbent assay (EIA)
3.
Immunofluorescence techniques (IF)
3.
Particle agglutination
4.
Neutralization tests
4.
Western blot (WB)
5.
Single radial hemolysis
5.
Recombinant immunoblot assay (RIBA), line
immunoassay (Liatek), etc.
6.
PCR methods.
21.1.5
Stains for Diagnosis of Viral Infections
Diagnosis of a viral infection based on microscopic examination of stained smears or
tissue sections is limited to virus that induce characteristic morphologic changes during
their replication in the cells they infect or for which specific antibodies to quantitatively
significant and stable antigens are commercially available. Morphologic features indica-
tive of a viral infection include the formation of inclusion bodies (masses of material con-
sisting of viral particles or excess accumulation of products of viral synthesis) in the host
cell nucleus, cytoplasm, or both, and for some virus, in the multinucleate giant cells [20].
21.1.6
Direct Detection in Smears
Microscopic examination of cells in stained smears as a mechanism for diagnosis of viral
infection was popularized in the late 1940s by Tzanck, who used this technique to study
cells scraped from the base of vesicular skin lesions as an aid to dermatologic diagnosis.
In particular, the Tzanck preparation allowed differentiation of herpes simplex virus
(HSV) or VZV infection, based on specific cytopathic changes, from other dermatologic
diseases with a similar clinical presentation [21-23]. Cytologic preparations of material
collected from a variety of sites have also proven useful for the detection of cytopathic
changes of several different virus [24-26].
To perform the Tzanck test, the lesion selected for study is cleaned, the vesicle or
pustule is opened and the crust is removed with a scalpel blade, the base is scraped
vigorously with the edge of the blade, and the cellular material collected is evenly spread
on a glass microscope slide. As originally described by Tzanck, the preparation is allowed
to air-dry and then stained with Giemsa or a Romanowsky polychrome dye, such as
Wright stain; Toluidine Blue O is an acceptable alternative. These stains are simple to use,
but air-drying results in poor definition of nuclear detail, which could make recognition
of cytopathic changes difficult. Modifications of the technique that allow better preserva-
tion of cellular detail and thus may be more sensitive than air-dried preparations include
