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 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 B- cells 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 T- cells 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, B- cells, 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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