virus presentation.pptx

old five kingdom classification of organisms.

Five kingdoms makes way for 3 Domains
BUT...now with DNA

Summary of differences!
Prokaryotic Cells Eukaryotic cells
small cells (< 5 mm) larger cells (> 10 mm)
always unicellular often multicellular
no nucleus or any membrane-bound
organelles
always have nucleus and other
membrane-bound organelles
DNA is circular, without proteins DNA is linear and associated with
proteins to form chromatin
ribosomes are small (70S) ribosomes are large (80S)
no cytoskeleton always has a cytoskeleton
cell division is by binary fission cell division is by mitosis or meiosis
reproduction is always asexual reproduction is asexual or sexual

http://videosift.com/video/BBC-Horizon-Why-
Do-Viruses-Kill

He is most famous as the founder of virology.
He discovered viruses by proving in filtration
experiments that the tobacco mosaic disease is
caused by something smaller than a bacterium He
named that new pathogen virus.
Martinus Willem Beijerinck was a microbiologist
and botanist
Discoverer of viruses
late 14c., "venomous substance," from L. virus "poison, sap of plants, slimy
liquid,"

Figure 19.2
Extracted sap
from tobacco
plant with
tobacco mosaic
disease
RESULTS
Passed sap
through a
porcelain filter
known to trap
bacteria
Healthy plants
became infected
Rubbed filtered
sap on healthy
tobacco plants
1 2 3
4

Noroviruses are the most common cause of acute gastroenteritis (infection of the stomach
and intestines) in the United States. Norovirus illness spreads easily and is often called
stomach flu or viral gastroenteritis,
People who are infected can spread it directly to other people, or can contaminate food or
drinks they prepare for other people. The virus can also survive on surfaces that have been
contaminated with the virus or be spread through contact with an infected person.
Sources Produce, shellfish, ready-to-eat foods
touched by infected food workers (salads,
sandwiches, ice, cookies, fruit), or any
other foods contaminated with vomit or
feces from an infected person
Incubation Period 12-48 hours
Symptoms Diarrhea, vomiting, nausea,and stomach
pain. Diarrhea tends to be watery and non-
bloody. Diarrhea is more common in adults
and vomiting is more common in children

Hepatitis A is a highly contagious liver infection caused by the hepatitis A virus.
The virus is one of several types of hepatitis viruses that cause inflammation and
affect your liver's ability to function.
You're most likely to contract hepatitis A from contaminated food or water or
from close contact with someone who's infected. Mild cases of hepatitis A don't
require treatment, and most people who are infected recover completely with no
permanent liver damage.
Practicing good hygiene, including washing hands frequently, is one of the best
ways to protect against hepatitis A. Vaccines are available for people most at risk.

Yellow fever, is an acute viral disease. In most cases, symptoms include fever, chills, loss of
appetite, nausea, muscle pains particularly in the back, and headaches. Symptoms typically
improve within five days. In some people within a day of improving, the fever comes back,
abdominal pain occurs, and liver damage begins causing yellow skin. If this occurs, the risk
of bleeding and kidney problems is also increased.
The disease is caused by the yellow fever virus and is spread by the bite of the
female mosquito. It only infects humans, other primates, and several species of
mosquitoes. The virus is an RNA virus. A safe and effective vaccine against yellow fever
exists and some countries require vaccinations for travellers.

Dengue fever is a painful, debilitating mosquito-borne disease caused by any one of four
closely related dengue viruses.
Each year, an estimated 100 million cases of dengue fever occur worldwide. Most of these
are in tropical areas of the world.
Dengue fever is transmitted by the bite of an Aedes mosquito infected with a dengue virus.
The mosquito becomes infected when it bites a person with dengue virus in their blood. It
can’t be spread directly from one person to another person.
Symptoms of Dengue Fever
Symptoms, which usually begin four to six days after infection and last for up to 10 days,
may include
Sudden, high fever
Severe headaches
Pain behind the eyes
Severe joint and muscle pain
Nausea
Vomiting
Skin rash, which appears three to four days after the onset of fever
Mild bleeding (such a nose bleed, bleeding gums, or easy bruising)

Viral Vectors
many viruses need vectors to transmit them from one host to
another
tick-borne encephalitis (TBE)
tick typhus
tick fever
aphid
plant viral diseases dengue fever
west nile virus
yellow fever
Ebola
rabies
How are
colds,
flu and HIV
spread?
Q:

SARS - respiratory disease
caused by a coronavirus

Structure of viruses
of protein
of protein
Protein coat may contain
protein spikes which help
penetrate host cells
Plant viruses
contain RNA
Animal viruses
contain DNA or
RNA

A virion, consists of nucleic acid surrounded by a
protective coat of protein called a capsid. Viruses
can have a lipid "envelope" derived from the host
cell membrane which assists the virion in entering
a host cell.

23
Viruses vary in size, as well as in shape
This is due to the
different cells they
target.

Capsid symmetry
Icosahedral Helical
Naked capsid
Enveloped
Lipid
Glycoprotein
Matrix

Figure 19.3a
20 nm
(a) Tobacco mosaic virus

Figure 19.3b
50 nm
(b) Adenoviruses

Icosahedral naked capsid viruses
Adenovirus
Electron micrograph
Foot and mouth disease virus
Crystallographic model
http://www.ncbi.nlm.nih.gov/ICTVdb/Images/Ackerman/Animalvi/Adenovir/799-16.htm
http://virology.wisc.edu/virusworld/ICTV8/fmd-foot-and-mouth-ictv8.jpg

Figure 19.3c
50 nm
(c) Influenza viruses

Figure 19.3d
50 nm
(d) Bacteriophage T4

Credit:
NORM THOMAS / SCIENCE PHOTO LIBRARY
Tobacco mosaic virus. Leaf of a tobacco
plant showing damage caused by the
tobacco mosaic virus.
This virus takes its name from the mosaic
effect of light and dark patches it causes
on the leaves. It is spread by contact
between infected plants, and can remain
active in contaminated soil for several
years. The virus is a serious pest of
tobacco plants, causing a reduction in the
quantity and quality of tobacco leaves

• Reproduce
• They have DNA or
RNA
• They can adapt to
surroundings
• They have
organization
• They are not made of
cells or organelles
• They cannot reproduce
without a host
• They don’t have both
DNA and RNA
• They do not metabolize
energy

How do viruses replicate?
2 methods of replication:
1. Lytic Cycle – the virus enters the cell,
replicates itself hundreds of times, and
then bursts out of the cell, destroying it.
2. Lysogenic Cycle – the virus DNA
integrates with the host DNA and the
host’s cell helps create more virus
DNA. An environmental change may
cause the virus to enter the Lytic Cycle.

In the lysogenic cycle,
the virus reproduces
by first injecting its
genetic material,
indicated by the red
line, into the host
cell's genetic
instructions.

37
VIRAL
LIFE
CYCLE
ATTACHMENT
PENETRATION HOST
FUNCTIONS
ASSEMBLY
(MATURATION)
Transcription
REPLICATION
RELEASE
UNCOATING
Translation
MULTIPLICATION
Click after each step to view process

Credit:
THOMAS DEERINCK, NCMIR / SCIENCE PHOTO LIBRARY
Viruses infect cells, hijack the cell's
internal machinery to replicate
themselves, then release hundreds of
clones from the cell's surface to infect
further cells.
This is Herpes simplex viruses (HSV)
(red and blue) are seen budding from the surface of a cell
(yellow).
HSV causes watery blisters on the skin, mucous membranes and
genitals.
Reproduction of viruses

Attachment is a specific binding between viral capsid proteins and specific receptors on the
host cellular surface. This specificity determines the host range of a virus. For example, the
human immunodeficiency virus (HIV) infects only human T cells, because its surface
protein, gp120, can interact with CD4 and receptors on the T cell's surface. This mechanism
has evolved to favour those viruses that only infect cells that they are capable of replicating
in. In some viruses attachment to the receptor induces the viral-envelope protein to
undergo changes that results in the fusion of viral and cellular membranes.

Penetration: following attachment, viruses enter the host cell through receptor mediated
endocytosis or membrane fusion.

Uncoating is a process that viral capsid is removed is degraded by viral enzymes or host
enzymes thus releasing the viral genomic nucleic acid.

Replication involves synthesis of viral messenger RNA (mRNA) for all viruses except positive
sense RNA viruses (see above), viral protein synthesis and assembly of viral proteins and
viral genome replication.
Crash course Biology http://www.youtube.com/watch?v=CeVtPDjJBPU&safe=active

Differences Between Lytic and Lysogenic Cycles
In the Lytic Cycle:
Viral DNA destroys Cell DNA, takes over cell functions and destroys the cell.
The Virus replicates and produces progeny phages.
There are symptoms of viral infection.
In the Lysogenic Cycle:
Viral DNA merges with Cell DNA and does not destroy the cell.
The Virus does not produce progeny.
There are no symptoms of viral infection.

South Africa has the highest prevalence of HIV/AIDS compared to any other country in the world with 5,6
million people living with HIV, and 270,000 HIV related deaths recorded in 2011. (UNAIDS). There are
approximately 52 million people in total in our country

Viral envelope
A piece of the cell membrane budded
off from the last of the human host
cell
Nucleic acid
Two identical strands of RNA that
contain the genetic blueprint for
making more HIV viruses
Surface proteins
These spikes allow HIV to attach to
receptors on the host cells T cells and
macrophages
Reverse Transcriptase
Two important copies of this enzyme
convert the RNA into DNA once inside
a host cell
Capsid
Protein coat that protects nucleic
acids (RNA) within

Credit:
PETER GARDINER / SCIENCE PHOTO LIBRARY
HIV replication. 1. The virus approaches the specific
host cell
1

2. The glycoprotein spikes on the
viral envelope attach to surface
proteins on a T- lymphocyte white
blood cell (left).
2.
T lymphocyte
Glycoprotein spikes
Viral RNA
Reverse transcriptase
DNA manufactured
from RNA and
Reverse transcriptase

3. The RNA
(ribonucleic acid)
genome (red) and
reverse transcriptase
enzyme (blue dots)
are injected into the
cell.
3

4. Reverse
transcriptase enzyme
transcribes the single-
stranded RNA to
double stranded DNA
(deoxyribonucleic
acid),
5. The viral DNA can
then integrate into a
host cell
chromosome.
4
5
vRNA
vDNA
vRNA
vDNA

6. The virus hijacks the cell's
machinery:
- protein synthesis causing it to
produce viral proteins (6.1).
and
- RNA synthesis causing it to
form viral RNA molecules (6.2)
6.1 6.2

7. The proteins assemble around
the RNA forming the viral cores,
which then bud from the cell,
taking part of the host's cell
membrane as an envelope.
7
http://www.youtube.com/watch?v=EqK1CYYQI
ug

Entry
HIV life cycle
HIV can only replicate (make new copies of itself) inside human cells. The process typically
begins when a virus particle bumps into a cell that carries on its surface a special protein
called CD4. The spikes on the surface of the virus particle stick to the CD4 and allow the
viral envelope to fuse with the cell membrane. The contents of the HIV particle are then
released into the cell, leaving the envelope behind.

Reverse Transcription and Integration
Once inside the cell, the HIV enzyme reverse transcriptase converts the viral RNA into DNA,
which is compatible with human genetic material. This DNA is transported to the cell's
nucleus, where it is spliced into the human DNA by the HIV enzyme integrase. Once
integrated, the HIV DNA is known as provirus.

Transcription and Translation
HIV provirus may lie dormant within a cell for a long time. But when the cell becomes
activated, it treats HIV genes in much the same way as human genes. First it converts them
into messenger RNA (using human enzymes). Then the messenger RNA is transported
outside the nucleus, and is used as a blueprint for producing new HIV proteins and enzymes.

Among the strands of messenger RNA produced by the cell are complete copies of
HIV genetic material. These gather together with newly made HIV proteins and
enzymes to form new viral particles. The HIV particles are then released or 'bud' from
the cell. The enzyme protease plays a vital role at this stage of the HIV life cycle by
chopping up long strands of protein into smaller pieces, which are used to construct
mature viral cores.

1. It attacks the very cells that are meant to protect us
against viral infection - the lymphocytes
Why is HIV so deadly?

2. Numbers:
- approx 100 000 viral particles are made from one
infected lymphocyte before it dies.
- it is possible for 10 billion viruses to be made in
one day.

3. It cant be easily detected:
- latent viruses hide in lymph cells
- viral coat made from lymphocyte membrane
reduces the chances of recognition

4. the virus keeps changing
- many mutations of the enzyme, thus many mutations
in the formation of HIV particles
- the gene for one of the envelope's proteins mutates at
1% per year per person, thus further increasing the
genetic diversity of the virus

5. The behaviour of humans - social animals
- the very behaviour that ensures our success as a species
(sexual reproduction) causes the spread of the disease.
- addiction in drug use makes needle use hard to control

Credit:
NIBSC / SCIENCE PHOTO LIBRARY
Colored scanning electron micrograph of a T-lymphocyte blood cell (green)
infected with Human Immunodeficiency virus (HIV) (red), causative agent of
AIDS.
The surface of the T-cell has a lumpy appearance with large irregular surface
protrusions. Smaller spherical structures on the cell surface are HIV virus particles
budding away from the cell membrane.
The virus has infected the T-cell, and instructed the cell to reproduce many more
viruses. By this viral budding the T- cell dies.

What is Pandemic
Influenza?
Pandemic -A pandemic is an outbreak of global
proportions. It happens when a novel virus
emerges among humans - it causes serious illness
and is easily human transmissible (spreads easily
from person-to-person)
In 1918-1919, a global
pandemic of “Spanish Flu”
killed about 50 million people
worldwide.

 Put simply, a pandemic covers a much wider geographical
area, often worldwide. A pandemic also infects many
more people than an epidemic. An epidemic is specific to
one city, region or country, while a pandemic goes much
further than national borders.
 An epidemic is when the number of people who become
infected rises well beyond what is expected within a
country or a part of a country. When the infection takes
place in several countries at the same time it then starts
turning into a pandemic Ebola virus in Zaire in 1976
 The case of influenza, seasonal outbreaks (epidemics) are
generally caused by subtypes of a virus that is already
circulating among people. Pandemics, on the other hand, are
generally caused by novel subtypes - these subtypes have not
circulated among people before.

6. Viruses are not alive – they are inanimate complex organic matter. They lack any
form of energy, carbon metabolism, and cannot replicate or evolve. Viruses are
reproduced and evolve only within cells.
7. Over 1016 human immunodeficiency virus genomes are produced daily on the
entire planet. As a consequence, thousands of viral mutants arise by chance every
day that are resistant to every combination of antiviral compounds in use or in
development.
8. The first human influenza virus was isolated in 1933. In 2005, the 1918 pandemic
influenza virus strain was constructed from nucleic acid sequence obtained from
victims of the disease.
9. The biggest known viruses are mimiviruses, which are 400 nanometers (0.0004
millimeters) in diameter. The viral genome is 1,200,000 nucleotides in length and
codes for over 900 proteins.
10. The smallest known viruses are circoviruses, which are 20 nanometers (0.00002
millimeters) in diameter. The viral genome is 1,700 nucleotides in length and codes
for two proteins.

1.Some parasitic wasps lay eggs in caterpillars, where they mature
into adult wasps. The wasp eggs contain a virus, encoded in the
wasp genome, which prevents the caterpillar from rejecting the
eggs.
2. There are a million virus particles per milliliter of seawater – for a
global total of 1030 virions! Lined up end to end, they would stretch
200 million light years into space.
3. The genetic information of viruses can be DNA or RNA; single or
double stranded; one molecule or in pieces.
4. The name virus was coined from the Latin word meaning slimy
liquid or poison.
5. Walter Reed discovered the first human virus, yellow fever virus,
in 1901.

Structure of Viruses
• Viruses are not true cells
• They are acellular
• Described as complex biochemical molecules
• The viral particle or single virus is called a virion
• A virus is a very small infectious particle consisting of
nucleic acid enclosed in a protein coat and, in some
cases, a membranous envelope
© 2011 Pearson

Viruses are obligate intracellular parasites, which
means they can replicate only within a host cell
Each virus has a host range, a limited number of
host cells that it can infect
•Bacteriophages, also called phages, are viruses that
infect bacteria
•They have the most complex capsids found among
viruses
•Phages have an elongated capsid head that encloses
their DNA
•A protein tail piece attaches the phage to the host
and injects the phage DNA inside

How are viruses spread
• A person with a cold can spread the infection by coughing
and/or sneezing.
• Viruses can be passed on by touching or shaking hands
with another person.
• Touching food with dirty hands will also allow viruses from
the intestine to spread.
• Body fluids, such as blood, saliva and semen, can contain
the infecting organisms and transmission of such fluids, for
example by injection or sexual contact, is important,
particularly for viral infections like hepatitis or AIDS.

 Capsid - The capsid is the protein shell
that encloses the nucleic acid
The capsid has three functions:
• it protects the nucleic acid from digestion by enzymes
• contains special sites on its surface that allow the virion to attach to a
host cell
• provides proteins that enable the virion to penetrate the host cell
membrane and, in some cases, to inject the infectious nucleic acid into the
cell's cytoplasm.
 Envelope - Many types of virus have a glycoprotein envelope surrounding the
nucleocapsid. The envelope is composed of two lipid layers interspersed with
protein molecules (lipoprotein bilayer) and may contain material from the
membrane of a host cell as well as that of viral origin.
 Nucleic Acid

Viruses depend on the host cells that they infect to reproduce.
When found outside of host cells, viruses exist as a protein coat or capsid, sometimes enclosed
within a membrane.
The capsid encloses either or RNA which codes for the virus elements.
While in this form outside the cell, the virus is metabollically inert. See photos below.
a cluster of influenza viruses,
each about 100 nanometers
(billionths of a meter) long;
both membrane and protein coat are visible.
Reproduction of viruses
the virus that causes
tobacco mosaic disease in
tobacco plants.

http://www.courses.fas.harvard.edu/~
biotext/animations/lyticcycle.html
http://www.courses.fas.harvard.edu/~biotext/
animations/lysogeny.html

Mutating viruses
Viruses can mutate when they copy the genetic
material
– Copy something wrong
– Mistake proves useful
– More powerful virus (more infectious)
Viruses don’t mutate often, except…
– Influenza
– HIV

Following the assembly of the virus particles post-translational modification of the viral
proteins often occurs. In some viruses, (e.g. HIV), this modification, (sometimes called
maturation), occurs after the virus has been released from the host cell.

Viruses are released from the host cell by lysis
(see below) . Enveloped viruses (e.g., HIV)
typically are released from the host cell by
“budding”. During this process, the virus
acquires its phospholipid envelope which
contain embedded viral glycoproteins.

In most viral infections, the immune system has the opportunity of attacking viral
particles in some stages of the infection (before viruses enter cells or when they are
liberated after their replication). It may also take place in infected cells during the protein
production or viral assembling phase. During these stages, antigens that appear in the
membrane of the infected cell can activate the immune response.. In some cases, such as
herpes viruses, infection can last for long periods of time without the presence of any
viral particles or surface antigens being expressed in the membrane of infected
cells. When this happens, the immune system is unable to fight the infection, because
there are not viral peptides to flag its presence. But eventually infection is reactivated
(causes are not yet well known) and new infectious virions are liberated.

Source of infection:
Shedding virus susceptible
Man > 99%
animals zoonosis
from animals to humans or from
humans to animals

Routes of entry:
sexual
Inhalation
inoculation
Blood
organ t/plant
ingestion
vertical

“vertical transmission”
• Some viruses can
cross the placenta
• Infection during
pregnancy can
damage the foetus
e.g. Rubella,

Chicken pox
•
Chickenpox is caused by the
varicella-zoster virus

Ebola virus
• RNA strand virus
– Coiled RNA in spike-covered envelope
from host cell
• Long rods (800-1000 nm)
• Replication = 8 hours
– Therefore, spreads rapidly

Natural Reservoir
Suspected to be a zoonotic (animal-
borne)
However, it is unknown what organism
carries it naturally without being
infected
Suspected vectors
• Bats
• Primates (in some cases, have been
confirmed)

Ebola hemorrhagic fever
Symptoms:
• Severe headache
• Weakness
• Muscle aches
As it progresses:
• Severe vomiting
• Abdominal pain
• Diarrhea
• Pharyngitis
• Conjunctivitis
• External bleeding
• Extremely high body temperature
• Prostration
Incubation Period: Anywhere from 2-21 days

Inclusion Body Disease
stargazing behavior,
tie themselves in a knot and they can't get out
of it
The condition, which is named for the
inclusions, or pockets of foreign material,
found inside the cells of affected animals, is
ultimately fatal.
arenaviruses

Courtesy of CDC
Be warned!. One sneeze can generate an
aerosol of enough cold viruses to infect an
entire regiment of soldiers!

Colds and
Flu
Well over 200 viruses are implicated in the
cause of the common cold; the
rhinoviruses are the most common.

What is the difference between
influenza (“the flu”) and a cold?
The flu is much worse than a cold. Cold symptoms and complications
are much milder that that of the flu.
Symptom Cold Flu
Fever Rare Usually high fever (102°F/39°C--
104°F/40°C), sudden on set, lasts
3-4 days
Headache Rare Usual, can be severe
Aches and pains Sometimes, mild Usual, often severe
Fatigue & weakness Sometimes, mild Usual, severe, may last 2-3 weeks
or more
Extreme fatigue Unusual Usual early onset, can be severe
Runny, stuffy nose Common Common
Sneezing Common Sometimes
Sore throat Common Common
Chest discomfort, coughing Sometimes, mild to moderate Can become severe
Complications Unusual Pneumonia, respiratory failure. Can
be life threatening
Prevention Frequent hand washing Annual vaccination and frequent
hand washing

1. Congestion
This could be a stuffy or runny nose, or a "full" feeling in the head. Sneezing is also common with colds.
2. Watery Eyes
Eyes could be runny, or you may just feel like you have more tears than usual.
3. Itching in Nose, Throat or Eyes
Itchiness or a feeling like you need to scratch inside your nose, throat and eyes is common with a cold.
4. Feeling Tired
You may feel like you have not had enough sleep or you just don't have the energy to do everyday activities.
5. Fever
Fever is rare in adults, but may be more common in children. If your fever goes above 101 degrees, it is probably more
than a cold and you should contact your doctor.
6. Cough
You may have a dry or productive cough. If you are coughing up green or yellow mucous and it is painful to cough, you
should contact your doctor. You should also call your doctor if you are coughing up bright red blood or bloody mucous.
This could be a sign of a more serious condition.
7. Headache
Headaches are very common when you have a cold. Congestion puts pressure on the sinus area causing your head to
hurt.
http://coldflu.about.com/od/cold/tp/coldsand
s.htm

Types of influenza viruses
• Influenza viruses are divided into three
main types: influenza A, B, and C
• A viruses – infect birds and other animals,
as well as humans
• A viruses – source of seasonal influenza
epidemics and all pandemics
• B and C viruses – infect humans only and
do not cause pandemics

Symptoms of influenza may include:
Fever and extreme coldness (chills shivering, shaking (rigor))
Cough
Nasal congestion
Runny nose
Body aches, especially joints and throat
Fatigue
Headache
Irritated, watering eyes
Reddened eyes, skin (especially face), mouth, throat and nose
In children: diarrhea and abdominal pain,

The typical symptoms of a cold
include cough, runny nose, nasal
congestion and a sore throat,
sometimes accompanied by
muscle ache, fatigue, headache,
and loss of appetite

1. Macrophages will engulf viruses and display viral antigens. Why does it do this?
2. What activates the helper T cells?
3. What do helper T cells activate
4. What do B cells give rise to?
5. What do plasma cells produce?
6. How do antibodies function?
7. What is the function of the cytotoxic T cells?
8. Where do memory cells come from and what is their function?

History of influenza
• 412 BC - first
mentioned by
Hippocrates
• 1580 - first pandemic
described
• 1580-1900 - 28
pandemics

Pandemic influenza in the 20th Century
1920 1940 1960 1980 2000
H1N1 H2N2 H3N2
1918 “Spanish Flu” 1957 “Asian Flu” 1968 “Hong Kong Flu”
20-40 million deaths 1 million deaths 1 million deaths

1918 Flu Pandemic Facts:
• May have killed as many people as the Black Death- bubonic plague
• The majority of deaths were from a secondary infection such as bacterial
pneumonia
• It killed between 2 and 20 % of those infected; normal mortality rate is 0.1 %
• It mostly killed young adults with more than half of the deaths in people
between 20 - 40 years old due to novel surface proteins on the virus.
• It killed as many as 25 million in the first 25 weeks, whereas HIV/AIDS has
killed 25 million in the first 25 years.

In 1918 children would skip rope to the rhyme (Crawford):
I had a little bird, Its name was Enza.
I opened the window,
And in-flu-enza

Emergency hospital, Camp Funston, Kansas 1918
Courtesy of National Museum of Health and Medicine

What can be done to slow
the spread of a pandemic?
• Vaccine:
– not expected to be available until later in a pandemic
• Antivirals:
– likely to be insufficient quantities, effectiveness unclear
• Disease containment measures:
– may be the only measures available in the early stages of
a pandemic
– may be helpful in slowing the spread of a pandemic,
allowing more time for vaccine production

Vaccine
• Because the virus will be new,
there will be no vaccine ready
to protect against pandemic
influenza at the start of a
pandemic
• Specific vaccine cannot be
made until the virus strain has
been identified and will take at
least 4-6 months to produce

Making vaccines
http://www.pbs.org/wgbh/nova/body/making-
vaccines.html

Antiviral drugs
• Likely to be the only major
medical countermeasure available
early in a pandemic
• Uncertainty about effectiveness
for treatment or prevention
• U.S. goal is to stockpile enough
antiviral drugs to treat 25% of the
U.S. population
Reproduced with permission from Roche Products Ltd. Tamiflu ®

Disease containment measures
• Isolation: restriction of movement/separation of ill
infected persons with a contagious disease
• Quarantine: restriction of movement/separation of well
persons presumed exposed to a contagious disease
• Self-shielding: self-imposed exclusion from infected
persons or those who may be infected
• Social distancing: reducing interactions between people
to reduce the risk of disease transmission
• Snow days: days on which offices, schools,
transportation systems are closed or cancelled, as if
there were a major snowstorm

HIV = Human Immuno Deficiency Virus
AIDS = Acquired Immunodeficiency Syndrome

• Macrophage engulfs virus and displays the viral proteins on its surface
(displaying who the badies are)
• These displaying macrophages activate helper T cells
• Helper T cells activate the cytotoxic T cells and the B cells
• The cytotoxic T cells destroy the infected body cells – they recognise infected
Cells because the infected cells also display the viral proteins on their membrane
• The B cells forms plasma cells which produce antibodies
• The antibodies stick to the antigens (these are the viral proteins displayed on the
Membranes of infected cells)
• Once the antigens have attached, the antigens clump together and viral
Replication can no longer occur

The immune system includes certain types of white blood cells. It also includes chemicals
and proteins in the blood, such as antibodies, complement proteins, and interferon. Some of
these directly attack foreign substances in the body, and others work together to help the
immune system cells.
Lymphocytes are a type of white blood cell. There are B and T type lymphocytes.
B lymphocytes become cells that produce antibodies. Antibodies attach to a specific antigen
and make it easier for the immune cells to destroy the antigen.
T lymphocytes attack antigens directly and help control the immune response. They also
release chemicals, known as cytokines, which control the entire immune response

Helper T helper cell assist other white blood cells in immunologic processes, including
maturation of B cells into plasma cells and memory B cells, and activation of cytotoxic T
cells and macrophages.
Cytotoxic T cells destroy virally infected cells and tumor cells, and are also implicated in
transplant rejection.
Memory T cells persist long-term after an infection has resolved. They quickly expand to
large numbers of effector T cells upon re-exposure to their cognate antigen, thus
providing the immune system with "memory" against past infections.
Regulatory T cells are crucial for the maintenance of immunological tolerance. Their
major role is to shut down T cell-mediated immunity toward the end of an immune
reaction
Natural killer T cells

HIV
• Retrovirus
• White blood cells (T helper cells) and glial cells of the
brain
• HIV is a lentivirus (slow acting)

Lab workers Health workers Counselors 139
Basic Terms
• Antigen: A substance which is
recognized as foreign by the immune
system. Antigens can be part of an
organism or virus, e.g., envelope, core
(p24) and triggers antibody production.
• Antibody: A protein (immunoglobulin)
made by the body’s immune system to
recognize and attack foreign substances

Helper T Cells – Key to the immune system
T4 multiplies when the body is invaded by
infection
T4 stimulates B cells(lymphocytes) to produce
antibodies and to produce cytotoxic cells(natural killer
cells) which destroy infected body cells
T4 stimulates the production of macrophages (big
eater white blood cells) which attack invading bodies

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