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When viruses infect cells, they often cause damage ( cytopathic effects ) that may include lysis of the host cells. Cytopathic effects can be visualized by growing host cells in a petri dish, covering the cells with a thin layer of agar, and then adding virus (see Isolation, Culture, and Identification of Viruses ). The virus will diffuse very slowly through the agar. A virus will enter a host cell, proliferate (causing cell damage), be released from the dead host cell, and then move to neighboring cells. As more and more cells die, plaques of dead cells will form ( [link] ).

During the course of a viral infection, the patient will mount an antibody response to the virus, and we can quantify those antibodies using a plaque reduction assay . To perform the assay, a serial dilution is carried out on a serum sample. Each dilution is then mixed with a standardized amount of the suspect virus. Any virus-specific antibodies in the serum will neutralize some of the virus. The suspensions are then added to host cells in culture to allow any nonneutralized virus to infect the cells and form plaques after several days. The titer is defined as the reciprocal of the highest dilution showing a 50% reduction in plaques. Titer is always expressed as a whole number. For example, if a 1/64 dilution was the highest dilution to show 50% plaque reduction, then the titer is 64.

The presence of antibodies in the patient’s serum does not tell us whether the patient is currently infected or was infected in the past. Current infections can be identified by waiting two weeks and testing another serum sample. A four-fold increase in neutralizing titer in this second sample indicates a new infection.

A photograph of wells showing a smooth purple background with white spots.
In a neutralization assay, antibodies in patient serum neutralize viruses added to the wells, preventing the formation of plaques. In the assay pictured, the wells with numerous plaques (white patches) contain a low concentration of antibodies. The wells with relatively few plaques have a high concentration of antibodies. (credit: modification of work by Centers for Disease Control and Prevention)
  • In a neutralization assay, if a patient’s serum has high numbers of antiviral antibodies, would you expect to see more or fewer plaques?


When a patient has elevated protein levels in the blood or is losing protein in the urine, a clinician will often order a polyacrylamide gel electrophoresis ( PAGE ) assay (see Visualizing and Characterizing DNA, RNA, and Protein ). This assay compares the relative abundance of the various types of serum proteins. Abnormal protein electrophoresis patterns can be further studied using immunoelectrophoresis (IEP) . The IEP begins by running a PAGE. Antisera against selected serum proteins are added to troughs running parallel to the electrophoresis track, forming precipitin arcs similar to those seen in an Ouchterlony assay ( [link] ). This allows the identification of abnormal immunoglobulin proteins in the sample.

IEP is particularly useful in the diagnosis of multiple myeloma , a cancer of antibody-secreting cells. Patients with multiple myeloma cannot produce healthy antibodies; instead they produce abnormal antibodies that are monoclonal proteins (M proteins). Thus, patients with multiple myeloma will present with elevated serum protein levels that show a distinct band in the gamma globulin region of a protein electrophoresis gel and a sharp spike (in M protein) on the densitometer scan rather than the normal broad smear ( [link] ). When antibodies against the various types of antibody heavy and light chains are used to form precipitin arcs, the M protein will cause distinctly skewed arcs against one class of heavy chain and one class of light chain as seen in [link] .

Questions & Answers

what z microbiology
Mwelwa Reply
microbiology is all about the scientific study of microorganisms, their life changes, their life span, structural punctuality and their phenomenon.
Best scope in microbiology
wat abut skin
whatis scope
what happened when someone died and what happened to the blood
Franca Reply
nice question
when you die you have no memory and the blood dry off
what microorganisms is all about?
And how many does the microorganisms is classified?
How are microbs organized
what is endoparasites and exo parasite and their example
Endo : inside the body Exo/ecto : outside or on the body
examples please
Louse for exo/ecto Helminths (worms) for endo
what's prokaryotic
mohaiminul Reply
A prokaryotic cell is a cell with no membrane bounds organelles
what are the main effect of parasite?
yunusa Reply
nutritional group of micro organism
Mana Reply
what are the charateristic bacteria, eukaryotes, and viruses have in commom
Ami Reply
what type of bacteria ismor serious
D N A ar purno rup ki
Ruba Reply
বাংলায় দেখবো DNA এর পূর্রন্যরুপ কি
what's microbiology
micro biology is the study of micro organisms,those being unicellular multicellular or a cellular
deoxyribonucleic acid is a long molecule that contains our unique genetic code.
Does the parasite/parasitology are under microbiology or not
Define bacteria
Bacteria are a type of biological cell & they constitute a large domain of prokaryotic microorganisms.
what kind of microbiology
hello what is main function of T and B cells
Ishaq Reply
T cells are involved in cell-mediated immunity while B cells are primarily responsible for humoral immunity (relating to antibodies)
what is hepatitis B
it's viral infection that attacks the liver and can cause both acute and chronic diseases. the virus is most commonly transmitted from mother to child during birth and delivery, as well as through contact with blood or other body fluids...
What are fundamental experiment of microbiology?
Lucky Reply
study of microscopic organisms, unicellular and multicellular
what are the characteristics of bacteria, viruses, and eukaryotes
bacteria-are living organism. contain a peptidoglycan/lipopolysaccharide cell wall. VIRUS-are considered as organic structure which interact with living organism don't have acell wall. they have many differents like bacteria size -large(1000nm) virus size-smaller(20-400nm). bacteria ribosomes presen
virus ribosomes absence. bacteria living organism. virus b/n living and non-living things
eukaryotic cell has a true membrane bond nucleus and has other membranous organelles that allow for compartmenalization of function
This answer is wrong
Jeffrey Reply
who discovered the growth curve
Joy Reply
Example of coccus bacteria
Nweke Reply
staphylococcus aureus
MRSA any bew information
pl. read any new information about MRSA
Any stru tural finding about novel corona virus
Examples of spiral bacteria
Nweke Reply
Example of Bacillus bacteria
another one
what is the desifection decontamination or sterilization
Sahra Reply
Is the removal of dangerous substances or germs from an area, objects or person
It is the removal of any pathogen, including their spores
removal of all forms of life including endospore
I think there is a difference between disinfection and sterilization... we should consider those....
disinfection deals with removing harmful microbes at the surface level it doesn't destroy or kill spores ( it uses oxidizing agents ,alcohols , phenolic comp ,aldehydes etc) but sterilization deals with total elimination of all forms of lives.(this uses heat, steam, radiation and chemicals)
disinfecting is preventing microorganisms while sterilization is killing of microorganisms completely
what is the meaning of Papanicolaou smear
it's Pap smear A test to check for abnormal cells in the cervix.

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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