Introduction break the balance and cause problems,
Viral Nanotechnology provide general idea about fast developing in the field of
immunology, virology, microbiology, chemistry, physics, and mathematical
science. Its role is by leading
researchers and practitioners, making it both
inclusive and essential resources for study and research.
by increasing demand of the applications the viral
nanotechnology is quickly expanding
Viral nanotechnology characterized Similarly as An note worthy
science that concerns itself with how to
utilize the sub-atomic modules those
unique separate science of molecular engineering only constructs. chances to
revolutionize practices in energy, biomedicine, health care, photonics,
catalysis, electronics, and public health are diverse by present potential
applications of viral technology
the demand for new
methods and techniques in the
prevention, diagnosis, and treatment of disease is considered as reasons for
fast growth of Viral Nanotechnology. There is also great application to be used
as methods for diagnostics, including the development of diagnostic substances
and novel imaging technologies for detecting disease and infectious agents (1)
What is Virus?
Viruses are small infectious agent that can exist everywhere ,
their diameters in nanometers level. it’s found in air, soil animals and human bodies. but most of them are harmless. Human immune
system protect the body against virus by generating antibodieswhich will recognize the virus and destroy it.
The viruses can break the
balance and cause problems, diseases when the human immune system is weak due
to multiple reasons, so called opportunist pathogen.Viruses depend on the host
for their survival and reproducing. Viruses have many important functions for
humans, plants, animals, and the environment. such as some of them protect the host against other
infections , by transferring genes among different species. In biomedical
research, scientists use viruses to insert new genes into cells
Structure of a virus
Virus particle composed of three
Nucleic acid ( DNA or RNA ) core of the virus
DNA or RNA holds all of the information for
virus and that makes it unique and
help to multiply.
Protein Coat (capsid) –covering
over the nucleic acid which protect it.
Lipid membrane (envelope) – which covers the
capsid. naked viruses haven’t envelop
Life cycle of a basic virus
lytic cycle include :
Adsorption process in which virus particle
attaches to a host cell.
DNA or RNA by inject the host cell.
replication process by cellular enzymes which
start making new virus particles
4. Relaease of the virus by newly formed viruses that kill the cell then and
search for a new host cell.
Different Types of Virus.
There are four main morphological virus types:
It composes of a single capsomere stacked around a central axis
to form a helical structure
rod-shaped or filamentous virions
short and highly rigid
long and very flexible.
The genetic materials, (DNA or RNA ), single-stranded RNA, but
ssDNA in some types , connected to the protein helix by interactions between
the negatively charged nucleic acid and positive charges on the protein.
Overall, the length of a helical capsid is related to the length
of the nucleic acid contained within it
examples as tobacco mosaic virus
Most infections viruses are icosahedral or close spherical with
chiral icosahedral symmetry. A normal icosahedron is the ideal method for
forming a close shell from sub-units.
each triangular face has 3 identical capsomeresthat give 60 for
it. Numerous viruses as rotavirus, have more than 60 capsomers and spherical
shape.Capsomeresare surrounded by hexons
they might be made out of various proteins.
A few types of viruses covered themselves one of the cell
layers, either the external film encompassing a contaminated host cell or
internal layers, for example, endoplasmic reticulum or nuclear layer get
external lipid bilayer known as a viral envelope.
This film is decorated by
proteins coded for viral genome and host genome; The flu and HIV viruses
utilize this technique
These infections have a capsid that is neither helical nor
icosahedral, and that may have additional structures, as protein tails or a
complex external layer. for example, Enterobacteria phage T4, have boggling
composition comprising of an icosahedral head
to a helical tail, which may have a hexagonal base plate with projecting
Virus has two types, DNA virus and RNA virus. The genome of DNA
virus is consisted of DNA, and similarly RNA is the genetic material of a RNA
Effect of Virus on human Health
Living organisms as animals,
plants, fungi, and bacteria are all subject to be infected by viral infection. However
Viruses select specific type of cells which want to invade.
What does the role of host in order to fight off a virus invasion ?
“immune response.” which
is created by Immune system produce
antibodies to protect the host against any foreign substances. Antibodies are
specific to each type of intruder, and new set of antibodies will have to be formed
for each new disease of infection. This process take several days. In the meantime,”interferons.”
which is produced by the cell infected by virus immediately to protect adjacent
cells production of antibodies.the benefit of interferon in viral treatment is
still under research and the mechanism
in case if viral infection ,
antiviral infection can be prescribed.
diseases caused by viruses
Diagnostic Methods of viruses
(1) Direct detection
(2) Virus isolation
1. Direct Examination of Specimen
Clinical specimen examined directly for the presence of virus particles,
virus antigen , and viral nucleic acids.
Electron Microscopy morphology /
immune electron microscopy
Light microscopy histological
appearance – e.g. inclusion bodies
immunofluorescence, ELISA etc.
Molecular techniques for the
direct detection of viral genomes
2. Indirect Examination = Virus
Ø Cell Culture
Confirmation by neutralization,
Ø Eggs pocks – haemagglutination, inclusion bodies
Ø Animals disease or death confirmation by neutralization
Titres increase of antibody between acute and convalescent
stages of infection , detection of IgM
in primary infection.
COMPLEMENT FIXATION TESTS (CFT)
SINGLE RADIAL HAEMOLYSIS
ENZYME LINKED IMMUNOSORBENT ASSAY
WESTERN BLOT (WB)
virus isolation cultured cells, eggs and laboratory animals are used. Cell
cultures more widely used for virus isolation in many laboratories. For cell
culturespreparation, tissue fragments are first dissociated, by using trypsin or collagenase. The cell suspension is
then placed in a flat-bottomed glass or plastic container (petri dish, a flask,
a bottle, test tube) together with a suitable liquid medium. e.g. an animal
serum. After a variable slack, the cells will attach and spread on the bottom
of the container and then isolation is started.
Primary and Secondary Cultures
cultures are performed by replacing the fluid two or three times per week .the
cells are separated from the vessel wall by either trypsin or EDTA since the
cultures become too crowded, and the remaining portions are used to initiate
both primary and secondary cultures, the cells keep some of their
characteristics from which tissue they are derived.
cultures are separated into 3 types:-
which are derived from animal or human tissues and can be sub-cultured only once
or twice e.g. primary monkey.
diploid cells – which are prepared from human fetal tissue and can be sub-cultured
20 to 50 times e.g. human diploid fibroblasts .
originate fromhuman cancer cells or
animal tissue e.g.
cultures vary greatly in their susceptibility to different viruses.
in cell culture :
Transportation of Specimens to the
laboratory should be as soon as possible once it’s taken.
Swabs should be placed in a bottle containing
virus transport medium.
Bodily fluids and tissues should be kept in a
of a specific virus grown in infected cell cultures can be performed by
neutralization of infectivity, hemadsorption inhibition, and mmunofluorescence.
Effects of productive viral
replication in cell culture:
effect(s) (CPE) as in mumps and measles
Advantages of cell culture for virus diagnosis :
period (up to 4 weeks) required for result.
to bacterial contamination.
to toxic substances which may be present in the specimen.
viruses will not grow in cell culture e.g. Hepatitis B, Diarrheal viruses,
in obtaining cell cultures.
Left:Haemadsorption of red
blood cells onto the surface of a cell sheet infected by mumps virus. Also note
the presence of syncytia which is indistinguishable from that of RSV (Courtesy
of Linda Stannard, University of Cape Town). Right: Positive CMV DEAFF
test. (Virology Laboratory, Yale-New Haven Hospital)
2. Electron Microscopy
It’s used for detection and
identification of virus’s morphology by EM.
identification of virus
to analyze multiple specimens
of minimum number of virus (around 106 virus particles per ml
is difficult for some viruses as SRSV
skilled personnel are required.
Types of EM methods;-
staining is used, small special equipment is required ,
Samples should be concentrated prior negative
staining by different methods as differential centrifugation,ammonium sulphate
microscopy (IEM). High sensitivity and specificity
It’s used in the following situations:
number of virus particle are available.
which have different morphological shapes as herpes viruses and picornaviruses
an outbreak conditions
Haemagglutination Inhibition Test
viruses directly agglutinate erythrocytes by binding
to specific receptor sites on the surface
of the erythrocyte and this characteristic can be used in detection,identificationandquantitation
Some virus will have ability to bind
to erythrocytes (red blood cells), causing the formation of a lattice. This characteristic
is called hemagglutination, Antibodies against the viral protein prevent virus to agglutinate
the erythrocytes , it’s known haemagglutination-inhibition test (HAI)
It’s widely used for the diagnosis
of rubella and influenza virus infections.
Rapidin detection and identification of virus(few hours)
4. ELISA (enzyme-linked
immunosorbent assay (ELISA) was developed in 1970 ,
also known as solid-phase enzyme immunoassay. It is biochemical
technique mainly used to detect the presence of specific antibody or antigen in
the sample. It has been used as marker for disease diagnosis.
techniques can be used in ELISA, the most important one are:
reaction between antigen bound with primary antibody in plate and antigen exist
in the sample.
of color is inversely proportional to
the concentration of antigen present in the sample.
§ Insolubilized antigen binds to the
analyte (the antibody) in the sample specifically,
§ addition of labelled enzyme linked
second antibody that binds to primary antibody.
§ Unbound antibody-enzyme conjugates are washed
used for detection of antibody present in the sample.
exist in the specimen bind specifically to the antigen
remove unbound antibodies wash the solution.
will conjugate secondary antibodies.
change after addition enzyme substrate.
of color direct proportional to concentration of primary antibodies.
extra incubation step is required
Higher sensitivity; – either by selection of antibodies with a extremely high
affinity, or by reduction of the height and variability of the background
reaction, which makes very low concentrations of analyte more readily
– by avoiding the presence of any antibody
in the assay system with specific reactivity against non-analyte epitopes, and
by selecting combinations of monoclonal antibodies which may further increase
3. Higher practicality; – e.g. by introducing simultaneous incubation of label,
solid phase and sample without risk of “prozone effect”.
5. Single Radial Haemolysis
radial haemolysis (SRH) is usually used for the detection of rubella-specific
serum can be analyzed simultaneously to confirm the immunity by
sensitive, specific, and reliable.
Immunofluorescence (IF) is commonly
used for rapid analysis of virus
basic principle by using a
fluorescein- labelled antibody to stain specific virus antigens present in the
samples, so that the stained cells fluoresces under UV illumination.
Direct IF, the specimen is probed directly with a specific labelled
antibody against specific virus antigen.
Indirect IF, the specimen is first probed with a non-labelled specific
antibody, followed by a labelled antibody against the first antibody.it has extra amplification step.
of virus antigen can be done by direct IF or indirect IF
of virus antibody can be determined always by indirect IF