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HUMAN VIRAL INFECTIONS
Aditya Singh
Personal Project Presentation
WHAT IS A VIRUS?
A virus is basically a tiny bundle of genetic material - either DNA or RNA - carried
in a shell called the viral coat, or capsid, which is made up of bits of protein called
capsomeres.
There are over 300,000 viruses on Planet Earth, but we are going to focus on 4 of
the more common ones:
Cold Virus
Influenza (Flu) Viruses
Viral Gastroenteritis (Stomach Flu)
HIV/AIDS
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COLD VIRUS
WHAT IS THE COLD?
The common cold is a viral infection of your upper
respiratory tract, your nose and throat. There are over
100 viruses that can cause a col, but the rhinovirus is
the most common culprit, and is highly contagious.
The cold virus enters your body through your mouth,
eyes, or nose. The virus can spread through in the air
when some someone who is sick coughs, sneezes, or
even talks. However, it also spreads by hand to hand
contact with an individual who has the cold or by
sharing contaminated objects.
HOW DOES THE HUMAN BODY FIGHT THE COLD?
There are 2 ways the human body can stop the cold virus from infecting the system, Innate
Immunity and Adaptive Immunity.
Innate Immunity is a natural immunity and
refers to nonspecific defense techniques
that activate immediately or within hours of
an antigen's existence in the body. A few
examples are skin, chemicals in the body,
and immune system cells.
Adaptive Immunity is antigen-specific immune response and it is
much more complex than innate. In this process, the antigen fist has
to be processed and recognized. Once that is completed, the
adaptive immunity system creates an army of immune cells
specifically designed to attack the antigen. Adaptive Immunity
also has a "memory", so that in the future, responses against that
specific antigen are more efficient and faster.
PROCESS OF THE BODY FIGHTING THE VIRUS
Innate Immunity:
Once the cold virus enters through the mouth, eyes, or nose, it goes to the body's first
line of defense consisting of barriers, they include skin, mucus membrane, and mucus
itself (much of the inside of the nasal cavity is lined with mucus). Its function is to trap
foreign particles before they enter the lungs.
However, some pathogens permeate the physical barriers. If this happens, large
cells called macrophages may engulf and eliminate certain pathogens. This is called
phagocytosis, and it kills the bacterial pathogen. Now if the virus escaped the
macrophages, adaptive immunity will take over.
PROCESS OF THE BODY FIGHTING THE VIRUS
Infection:
Since the virus has escaped the first lines of defense, it will start infecting cells. The
virus will now bind to receptors on certain nasal cells. Part of the virus enters the cell
and this often triggers an inflammatory response which can cause swelling and a
runny nose.
The cold virus genetic material is able to command the cell to make more virus
particles to be spread throughout the body. Then the virus lyse the cell and are free
to infect other cells.
PROCESS OF THE BODY FIGHTING THE VIRUS
Adaptive Immunity:
Now that the virus has gone through innate immunity, adaptive immunity responses will now
begin. The immune system uses several lines of defense against the virus now and some of the
virus will find its way to B-cells in the lymph. There are millions of different B-cells that exist in
your body, each with different receptor proteins. A small number of these cells have the
receptors needed to attach to this particular cold virus.
Once a virus binds to a B-cell receptor, the B-cell engulfs the virus into a lysosome within the
cell. Enzymes in the lysosome are now used to digest the virus and pieces of the virus are
presented on the outside of the B cell, where this viral antigen acts as a signal to T cells in the
body. Now the T-helper cells recognize this as a foreign object, so they bind to the B cell. The T
helper cell release chemical signals (cytokines) now which signal the B cell to multiply. The Bcells become antibody factories now and they produce an abundant amount of antibodies
against that cold virus.
Lastly, some of these B-cells become memory cells and can rapidly produce antibodies that
recognize this virus if that body encounters the same specific cold virus again.
MEDICINES
Doctors are able to diagnose a cold based on
the symptoms present on the patient. Antiviral
drugs and antibiotics are not recommended to be
used for a cold, but instead, over-the-counters
drugs are optional to ease the symptoms and not
the actual infection. However, if the cold gets out
of hand and the symptoms are getting worse, then
some medications may be taken, but it all depends
on the doctor's diagnosis.
INFLUENZA VIRUS
WHAT IS INFLUENZA?
Influenza, more commonly known as the flu, is a respiratory illness
caused by a virus that infects the cells lining the lungs, nose, and
throat. To infect your cells, the virus has to enter them. The virus
can enter through any part of the body, like the mouth, eyes, nose,
etc., or it can go on the hand if contact is made with it, and then
eventually go into the body, if the hand is put on the previous
places mentioned.
There are many types of influenza viruses, but only types A, B,
and C can cause the flu. Type A and B viruses are responsible for
the large flu epidemics. Type C flu virus is more stable and usually
causes mild respiratory symptoms. influenza spreads around the
world in a yearly outbreak, resulting in about three to five million
cases of severe illness and about 250,00 to 500,000 deaths.
HOW DOES THE HUMAN BODY FIGHT INFLUENZA?
Influenza is an illness caused by a virus infecting the cells lining the lungs, nose, and throat. However,
once the virus enters the body, it first has to go through the body's first line of defense. This defense
consists of barriers to foreign substance, some of the barriers include skin, mucus membrane, and mucus
itself, but much of the nasal cavity is lined with mucus and is set up to trap foreign particles before they
enter the lungs.
Now if the virus is able to pass those defenses and escape the macrophages, the virus will now begin to
enter a host cell. First, the hemagglutinin protein on the virus binds to a receptor on the cell. The binding
of the virus causes the cell to undergo endocytosis. Once inside, the virus takes over the cell and begins to
create more to infect in a larger quantity. Viruses use the machinery of the host cell to make new copies
of their genetic material and to make proteins.
CONTINUED…
The body fights influenza infections by developing
antibodies to the hemagglutinin on the virus. When
antibodies attach to hemagglutinin, they keep the virus
from attaching to healthy cells which keeps the virus from
infecting them. However, as each body cell is taken over by
an invading virus, it sends out a distress signal as MHCs
(transport chemicals from inside the cell to the cell surface)
carry viral proteins to the surface which are brought to the
attention of killer T-cells. Immediately they see the distress
signal, coat the cell with toxic chemicals killing it and the
virus.
CONTINUED…
Now the macrophages come in to clean up the mess
while being aided by histamine, which boosts the
blood flow to the infected are to get more white blood
cells in (killer T-cells and others).
While that is happening, a single B-cell in the gland
recognizes the viral material, multiplies, and begins to
release a flood of antibodies, over 2000 per second.
The tiny antibodies spread rapidly through your body
fluids to the site of the infection. There they lock on to
the virus and prevent it from cloning itself.
CONTINUED…
This stellar combination of antibodies, T-cells, and macrophages
begin to take its toll on the virus and the virus dies. However, if Tcells and antibodies go on multiplying, they would overwhelm the
body, just like cancer. So the T-cells turn their toxic effects on
themselves and the B-cells. Only a few survive, which become
memory cells, ready to fight instantly if the same virus infects the
body again.
MEDCINES
Flu Vaccine:
Influenza has many medicines and treatments available. However, it
also has a vaccine. The flu vaccine causes antibodies to develop in
the body about two weeks after vaccination and these antibodies
will provide protection against infection with the viruses that are in
the vaccine.
The seasonal flu vaccine protects against influenza viruses and the
traditional vaccines (called trivalent vaccines) are made to protect
against three flu viruses; influenza A (H1N1) and (H3N2), and
influenza B. In addition, there are flu vaccines made to protect
againdt four vaccines called quadrivalent vaccines. These vaccines
protect against the same viruses as the trivalent vaccine and an
additional B virus. In conclusion, flu vaccines are a precaution that
everyone should take, but in the event you obtain influenza, you have
the option of also taking antiviral drugs.
MEDICINES
Antiviral drugs:
Antiviral medications are prescription pills, liquids,
or inhalers used to prevent or treat flu viruses. There
are four antiviral drugs approved for treating flu in
the United States - oseltamivir (Tamiflu), zanamivir
(Relenza), amantadine (Symmetrel), rimantadine
(Flumadine), and peramivir (Rapivab).
VIRAL GASTROENTERITIS
WHAT IS VIRAL GASTROENTERITIS?
Viral Gastroenteritis or more commonly known as the stomach flu is
swelling or inflammation of the stomach and intestines from a virus. This
infection can lead to diarrhea and vomiting. Gastroenteritis can affect
one person or a group of people who all ate the same food or drank
the same water. The germs may get into your system directly from food
or water or by way of objects such as plates and eating utensils.
There are many types of viruses that can cause gastroenteritis, but the
most common ones are:
Norovirus is common among school age-age children. It may also cause outbreaks
in hospitals and on cruise ships.
Rotavirus is the leading cause of severe gastroenteritis in children. It can also
infect adults who are exposed to children with the virus, and people living in
nursing home.
Astrovirus
Enteric Adenovirus
HOW DOES THE HUMAN BODY FIGHT VIRAL
GASTROENTERITIS?
Viral Gastroenteritis is highly contagious and this virus enters your body either by
touching somebody or something that is contaminated, but the virus is also present in
an infected person's stool and vomit. So the virus can become airborne anytime with
everyone vulnerable to it. The body is able to fight off the virus on its own, but it is
only able to if the body has lots of fluids and electrolytes since much of it is lost
through the illness.
CONTINUED…
Once the virus is inside the human body, it moves to the stomach area and
enters the small intestine where it begins to multiply. The lining of the small
intestine has appropriate attachments for the virus which allows the virus to
attach itself and release its genome.
Those genes then shut down the normal functions of the cell and start to take
over the cell to produce more viruses. The cells then lysis or explode releasing
more copies of the virus.
While this is happening the immune system recognizes that cells are dying
and T-cells allow your body to mount an immune response against it. They go
to B-cells and produce antibodies. These antibodies then travel to the small
intestine and inactivate the virus.
Lastly, your body becomes immune to the particular virus strand and memory
cells are created if more antibodies are needed in the future for that
particular strand.
MEDICINES
There is often no specific medical treatment for viral gastroenteritis, treatment mainly consists
of self care measures. Also, there is no specific vaccine made to prevent viral gastroenteritis
so the only way to truly prevent it is by having good hygiene. However, it is also advised to
drink lots of fluids and especially drinks with electrolytes, and of course, there are over the
counter drugs for any symptoms that need to be addressed.
HIV/AIDS
WHAT IS HIV & AIDS?
First, HIV stands for Human Immunodeficiency Virus and AIDS stands for
Acquired Immunodeficiency syndrome. HIV is the virus that can lead to AIDS,
which is life threatening. Unlike other viruses, the human body cannot get rid of
HIV, so once you obtain it, it is there for life.
HIV most often spreads through unprotected sexual intercourse with an infected
person. It may also spread by sharing drug needles or through contact with the
blood of an infected person. Also, women can give it to their babies during
pregnancy or childbirth.
In addition, HIV belongs to a special class of viruses called retroviruses. Within
this class, HIV is placed in the subgroup of lentiviruses. Other lentiviruses inclue
SIV, FIV, Visna and CAEV, and these mainly cause diseases in animals like
monkeys, sheep, and even more.
What the virus does is that it specifically attacks lymphocytes called T-cells. This
process involving destroying T-cells damages the body's ability to fight off
invading germs and diseases. So when the T-cells drop, people become more
susceptible to infections and this weakened immunity is known as AIDS.
HOW DOES THE HUMAN BODY FIGHT HIV?
HIV is a virus that can never be erased from your system, so the human body
tries to fight it, but it is very difficult. When the virus first enters the body, it
attacks specific lymphocytes called T-cells, it takes them over, and multiplies.
This process destroys more T-cells and it weakens the immune system greatly.
However, HIV can replicate inside human cells. This process typically begins
when a virus bumps into a cell that carries on its surface a special protein
called CD4. The spikes on the surface of the HIV particle stick to the CD4 and
allow them to fuse. The contents of the HIV virus are then released into the
cell. Then, HIV infects the cells (T-helper cells) that form the body's immune
system. As HIV infects more cells, the immune system becomes weaker. This can
lead to a person developing AIDS, however, treatment and medicines protect
the cells keeping the immune system strong and preventing AIDS, but the body
still has the HIV virus.
CONTINUED…
Once inside the cell, the HIV enzyme called reverse transcriptase converts the viral RNA
into DNA. This DNA is then transported to the cell's nucleus, where it is inserted into the
human DNA by the HIV enzyme integrase. Once inserted, the HIV DNA is known as
provirus. It is at this point that HIV affects the cell in a way that it begins to die and
weakening the immune system.
In addition, HIV provirus may lie dormant within a cell for a long time, but when the cell
becomes activated, it treats HIV genes the same way as human genes. First it converts
them into messenger RNA and then the messenger RNA is transported outside the
nucleus, and is used as a blueprint for producing new HIV proteins and enzymes.
There is no way for the human body to get rid of HIV from the body because of the
effects of the virus. With an HIV Infection, the process of macrophages, T-helper calls, Bcells, and antibodies working together doesn't work adequately. However, the
antibodies are effective at first eliminating much of the infection, but there are still some
viruses that escape. Then those viruses will infect more T-helper cells so that the infection
can spread throughout the body. Besides T-cells, HIV is capable of infecting any cell in
the body and can cross any barrier or border in the body. HIV is a strong and unique
virus that can completely destroy the immune system, health, and can lead to death
when it eventually turns into AIDS.
MEDICINES
There is no cure for HIV, so once someone has it, the virus will never leave their body. The purpose of the
available drugs and treatments is to keep the nervous system strong and minimize the effect of the virus and
try to keep it dormant.
In the early 1980's, when the HIV/AIDS epidemic began, patients rarely lived longer than a few years, but
today, there are many effective medicines to fight the infection, and people with HIV have longer, healthier
lives.
There are five major types of medicines for HIV:
Reverse Transcriptase (RT) Inhibitors- interfere with a critical step during HIV life cycle and keep the virus from making copes of itself.
Protease Inhibitors- interfere with a protein that HIV uses to make infectious viral particles
Fusion Inhibitors- block the virus from entering the body's cells
Integrase Inhibitors- block an enzyme HIV needs to make copies of itself
Multidrug Combinations- used to target 2 areas at once
These medicines help people with HIV, but they are not perfect. They do not cure HIV/AIDS, people with an
HIV infection still have the virus in their bodies. Also, they can still spread HIV to others through unprotected
sex and needle sharing, even when they are taking their medicines.
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