Assay of viral particles.

1. ASSAY OF VIRAL PARTICLES.
PRESENTED BY
IDOWU TEMITAYO .O.
MATRIC NUMBER: 0903010024
DEPARTMENT OF BIOLOGICAL
SCIENCES,
COLLEGE OF NATURAL SCIENCES,
JOSEPH AYO BABALOLA UNIVERSITY,
IKEJI-ARAKEJI,
OSUN STATE.

2. OUTLINE
DEFINITION OF TERM.
VIRAL GROWTH RECOGNITION.
COMMONLY USED LABORATORY METHODS
FOR THE DETECTION OF VIRUSES.
QUANTIFICATION OF VIRUSES.
TRADITIONAL METHODS.
MODERN METHODS.
CONCLUSION.

3. DEFINITION OF TERMS
WHAT ARE VIRUSES?
“A PIECE OF BAD NEWS WRAPPED UP IN A PROTEIN”
WHAT IS AN ASSAY?
ASSAY IS AN INVESTIGATIVE (ANALYTIC) PROCEDURE
IN LABORATORY MEDICINE, MICROBIOLOGY,
ENVIRONMENTAL BIOLOGY, AND MOLECULAR
BIOLOGY FOR QUANTITATIVE ASSESSING OR
QUALITATIVELY MEASURING THE PRESENCE OR
AMOUNT OR THE FUNCTIONAL ACTIVITY OF A
TARGET ENTITY (Mckean et al., 2005).

4. VIRAL GROWTH RECOGNITION.
Recognition of a diseased state
Systemic infection.
The production of a local lesion such as
plaque.
In tissue culture the culture will undergo
change with the production of cytopathic
effect (CPE), namely the destruction of the
cell, syncytia formation, or cellular
transformation.

5. Plate 1: CYTOPATHIC EFFECT (CPE)
Source: Wikipedia

6. COMMONLY USED LABORATORY
METHODS FOR THE DETECTION OF
VIRUSES.
Measure of virus infectivity.
Examination of viral serology (that is,
host antibody responses to the virus).
Molecular methods.

7. QUANTIFICATION OF VIRUSES
• TRADITIONAL METHOD-: These are industry
standard methods that have been used for
decades but are generally slow and labour
intensive.
• MODERN METHOD-: These are relatively new
commercially available product and kits that
greatly reduce quantification time.

8. TRADITIONAL METHOD

9. PLAQUE ASSAY
Plate 2: Viral Plaques of Herpes Simplex Virus.
Source: Wikipedia

10. FLUORESCENT FOCUS ASSAY (FFA):
Plate 3: Fluorescent Focus Assay
Source: C.D.C

11. 50% TISSUE CULTURE INFECTIVE DOSE
(TCID50)
This endpoint dilution assay quantifies the
amount of virus required to kill 50% of
infected hosts or to produce a cytopathic
effect in 50% of inoculated tissue culture cells.

12. PROTEIN ASSAY:
There are several variations of protein-
based virus quantification assays.
In general, these methods quantify either
the amount of all protein or the amount of a
specific virus protein in the sample rather
than the number of infected cells or virus
particles.

13. HEMAGGLUTINATION ASSAY:
The hemagglutination assay (HA) is a common
non-fluorescence protein quantification assay
specific for influenza.
SINGLE RADIAL IMMUNODIFFUSION
ASSAY:
Single Radial Immunodiffusion Assay, also
known as the Mancini method, is a protein
assay that detects the amount of specific viral
antigen by immunodiffusion in a semi-solid
medium (e.g. agar).

14. MODERN METHODS

15. Flow cytometry:
MODERN METHODS:
 A virus counter quantifies the number of intact
virus particles in a sample using fluorescence to
detect proteins and nucleic acids.
Quantitative Polymerase Chain Reaction
(qPCR):
Quantitative PCR utilizes polymerase chain reaction
chemistry to amplify viral DNA or RNA to produce
high enough concentrations for detection and
quantification by fluorescence.

16. Enzyme-Linked Immunosorbent Assay
(ELISA):
 ELISA is a more modern variation of a protein
assay that utilizes a specific antibody linked to
an enzyme to detect the presence of an
unknown amount of antigen (i.e. virus) in a
sample.

17. CONCLUSION
A basic principal of science is
measurement or quantitation,
therefore being able to accurately
quantify virus numbers became a
necessity.