Why Is Hiv So Evasive What Is The Hiv Reservoir
Although HIV can be controlled by antiretroviral therapy, it cannot be eliminated from the body. This is because HIV evades the normal immune system mechanisms for getting rid of cells infected by viruses.
HIV integrates itself into the DNA of human immune system cells and only replicates when the cell is stimulated to respond to an infection. These cells are called latently-infected cells. These cells are not recognised as infected by the immune system and killed off, allowing them to persist for as long as the cell lives.17
Some of the cells infected by HIV are very long-lasting memory T-cells. Reservoirs of latently- infected cells become established in the lymph nodes, the spleen and the gut. HIV also infects cells in the brain, but it is unclear if HIV can pass from the brain to other parts of the body. HIV may also persist for many years in macrophages immune cells found largely in tissues and in dendritic cells, which recognise infectious agents and alert other immune cells to remove them.
Latently-infected cells can proliferate without being activated and HIV may also pass from cell to cell within tissues in the gut and other reservoirs. 18 This means they evade the immune system and are not suppressed by antiretroviral drugs before infecting other cells.
Hiv Prevention: How To Avoid Infection
The main way of avoiding infection is to avoid activities that put you at risk. The three main ways of doing this are to
Always use a condom
This is not a guaranteed method of avoiding infection, but using a condom reduces the risk considerably. It must be worn all the way through sex.
Don’t share syringes
Avoid using recreational drugs that are injected with a syringe. Do not share syringes or needles with others.
Avoid blood transfusions
Avoid blood transfusions in certain countries, where they may not test the blood for HIV.
What Is Hiv What Is Aids
HIV is a virus that attacks the immune system, the bodys natural defense system. Without a strong immune system, the body has trouble fighting off disease. Both the virus and the infection it causes are called HIV.
White blood cells are an important part of the immune system. HIV invades and destroys certain white blood cells called CD4+ cells. If too many CD4+ cells are destroyed, the body can no longer defend itself against infection.
The last stage of HIV infection is AIDS . People with AIDS have a low number of CD4+ cells and get infections or cancers that rarely occur in healthy people. These can be deadly.
Having HIV does not mean you have AIDS. Even without treatment, it takes a long time for HIV to progress to AIDSusually 10 to 12 years. If HIV is diagnosed before it becomes AIDS, medicines can slow or stop the damage to the immune system. With treatment, many people with HIV are able to live long and active lives.
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Adaptive Immune Response To Hiv
Cellular immune response to HIV. The cellular immune response is induced upon the entry of HIV into the target cells and synthesis of viral proteins . MHC class I on the cell surface displays the intracellularly degraded HIV peptide fragments for recognition by T-cell receptors on CD8+ T cells . CD8+ T cells lyse HIV infected cells and secrete cytokines, i.e. interferon- , tumor necrosis factor , and chemokines, i.e. MIP-1 , MIP and RANTES, that inhibit virus replication and block viral entry into CD4+ T cells. Development of CD8+ T cells is crucial for control of HIV replication. This results in declining viraemia after primary infection. In the early stages of infection, CD4+ T cells lose their proliferative capacity and therefore their contribution to viral control is minor. However, during chronic infection CD4+T cells are present and secrete interleukin-2 or cytokines, such as IFN-, to control viraemia.
Figure 3.
Reverse Transcription And Integration
The viral capsid contains the enzymes necessary for the synthesis of new viral particles from the RNA strands by using cellular machinery of the host cell. One of these enzymes is the reverse transcriptase that synthesizes a double stranded DNA molecule from the existing viral ssRNA. The enzyme first creates a single stranded DNA from viral ssRNA, which is termed as reverse transcription. Using this DNA strand as a template, the enzyme then creates the second strand of DNA molecule, thus giving rise to a dsDNA molecule. The virus does not have its own set of nucleotide bases, and uses those present in the cytoplasm of the T-helper cells.
The dsDNA is tightly bound to a viral enzyme called integrase, and is transported into the nucleus by the cellular transport machinery of T-helper cells. Inside the nucleus, integrase enables the integration of the viral DNA into the DNA of T-helper cells. Using this mechanism the virus can hide and stay in the body in a latent state for several years.
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How Is Hiv Treated
Treatments for HIV typically involve antiretroviral therapy. This isnt a specific regimen, but instead a combination of three or four drugs. The U.S. Food and Drug Administration has currently approved nearly 50 different medications to treat HIV.
Antiretroviral therapy works to prevent the virus from copying itself. This maintains immunity levels while slowing the progression of HIV.
Before prescribing medication, a healthcare provider will take the following factors into consideration:
- a persons health history
- the levels of the virus in the blood
HIV doesnt cause a lot of outward or noticeable symptoms until the disease has progressed. For this reason, its important to understand how HIV is transmitted and the ways to prevent transmission.
HIV can be transmitted by:
- having sex, including oral, vaginal, and anal sex
- sharing needles, including tattoo needles, needles used for body piercing, and needles used for injecting drugs
- coming into contact with body fluids, such as semen, vaginal fluid, blood, and breast milk
HIV is not transmitted by:
- breathing the same air as a person living with HIV
- getting bitten by a mosquito or other biting insect
- hugging, holding hands with, kissing, or touching a person living with HIV
- touching a door handle or toilet seat thats been used by an HIV-positive person
Keeping this in mind, some of the ways a person can prevent HIV include:
Symptoms can take years to appear, which is why its so important to get tested regularly.
Why The Immune System Fails To Kill Hiv
- Date:
- Karolinska Institutet
- Summary:
- Our immune system contains CD8+ T cells which protect us from various diseases such as cancer and viruses. Some of them are specifically tasked with killing cells infected with the HIV virus and researchers have for the first time identified a key explanation for why these cells are unsuccessful in their task. In simple terms, the immune system’s ignition keys have not been turned all the way to the start position, which would enable the CD8+ T cells to kill the cells infected with HIV.
Our immune system contains CD8+ T cells which protect us from various diseases such as cancer and viruses. Some of them are specifically tasked with killing cells infected with the HIV virus — and researchers from Karolinska Institutet in Sweden, together with international colleagues, have for the first time identified a key explanation for why these cells are unsuccessful in their task. In simple terms, the immune system’s ignition keys have not been turned all the way to the start position, which would enable the CD8+ T cells to kill the cells infected with HIV.
It has long been known that CD8+ T cells that are meant to target and kill the HIV virus lose important functions they become exhausted and cannot complete their task. In one study, published in the journal PLOS Pathogens, researchers have successfully shown at the molecular level what it is that weakens these important CD8+ T cells.
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Why Does The Immune System Fail To Fight The Hiv Virus
There are various reasons which can contribute to the failure of the immune system to control HIV infection and prevent AIDS development. By infecting CD4+ T cells, HIV is able to replicate predominantly in activated T cells and paralyse one of the main components of adaptive immune system. HIV can also establish latent infection in CD4+ T cells and remain invisible to CD8+ T cells and therefore replication can occur later in the infection and generate new virions. Antigenic mutation within the T-cell epitopes can affect the binding capacity of MHC molecules to the viral peptides, resulting in the inability of the TCRs to recognise the MHC-peptide complex. Finally, HIV is able to hide from anti-HIV antibodies by expressing non-immunogenic glycans on key antibody epitopes.
Preventive Treatment Before Exposure
Taking an antiretroviral drug before being exposed to HIV can reduce the risk of HIV infection. Such preventive treatment is called preexposure prophylaxis . However, PrEP is expensive and is effective only if people take the drug every day. Thus, PrEP is recommended only for people who have a very high risk of becoming infected, such as people who have a partner who is infected with HIV.
PrEP may also be recommended for people who engage in high-risk sexual activities, such as the following:
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Men who have anal sex with men without using a condom
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Heterosexual men and women who do not regularly use condoms during sex with partners whose HIV status is unknown and who are at increased risk of HIV infection
People who use PrEP still need to use other methods to prevent HIV infection, including consistent use of condoms and not sharing needles to inject drugs.
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Progression From Hiv To Aids
In the final stage of HIV, a patients T-cell count falls as viral load increases the immune system becomes severely compromised. When the patient is diagnosed with a stage-4 HIV-related condition such as tuberculosis or cancer or pneumonia, the virus has made its progression to AIDS, Acquired Immunodeficiency Syndrome. Many of the symptoms and sickness at this point may be from opportunistic infections and not from AIDS itself. Once the virus has progressed to AIDS, the body is more likely to fail, though the time left to a patient ranges anywhere from just a few months to many years.
To learn more about what happens when HIV becomes AIDS, watch the video below, courtesy of YouTube:
What To Do If You Are Exposed To Hiv
If you have been exposed to infection, you should contact a doctor as soon as possible for advice, testing and treatment. In the UK, the best place to go is a sexual health clinic or specialised HIV clinic because they’re used to dealing with possible HIV cases and their technical facilities are very good.
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Hiv Effects On The Nervous System
About half of people with AIDS have nerve problems related to the virus. Infection or inflammation can damage your spinal cord or brain and keep your nerve cells from working the way they should. Some medications can also affect your nervous system.
Brain
Inflammation in your brain and spinal cord can lead to confusion and other thinking problems as well as weakness, headaches, seizures, and balance problems.
When AIDS is far along, you might get dementia and have problems remembering things.
Having HIV can also affect your mental health. Many people living with it have depression or anxiety. Mental health professionals and support groups can help you work through your concerns and manage your life with HIV.
Nerves
The opportunistic infection cytomegalovirus can attack your nerves, making it hard for you to control your arms and legs or your bladder.
Itâs common for tiny holes to form in spinal fibers when people with AIDS donât get treatment. This is called vacuolar myelopathy and causes trouble walking.
HIV or the drugs that treat it can also damage nerves all over your body, causing neuropathy. You might have pain, numbness, weakness, burning, stiffness, or tingling.
Antiretroviral therapy to treat HIV can lower your risk of getting these conditions or complications. If a medication is causing the problems, your doctor might switch you to a different one.
Hiv Effects On The Circulatory System
Several things make your chances of heart-related problems go up. Because HIV affects your immune system, your body will be inflamed as it tries to fight the infection, like itâs on a constant simmer. This kind of inflammation has been linked to heart disease.
Some drugs you take for HIV can also make heart disease more likely. They can cause insulin resistance, which makes you more likely to get diabetes, and problems breaking down fats. Diabetes, in turn, raises your risk of heart disease. You might need medicines to control your blood sugar and cholesterol.
If you smoke, quit. Eat a variety of vegetables and fruits, plenty of whole grains, and foods with omega-3 fatty acids. Choose lean cuts of meat and low-fat dairy products. Exercise, like taking a brisk walk, for 20 to 30 minutes most days of the week.
If you’re carrying extra weight, losing as little as 5 or 10 pounds could make a big difference.
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How Do People Get Hiv
HIV spreads when infected blood or body fluids enter the body. This can happen:
HIV also can pass from mother to child during pregnancy, childbirth, or breastfeeding.
HIV is NOT spread through:
- pee, poop, spit, throw-up, or sweat
- coughing or sneezing
- sharing eating utensils or drinking glasses
Screening And Diagnostic Tests
If doctors suspect exposure to HIV infection, they do a screening test for HIV. Doctors also recommend that all adults and adolescents, particularly pregnant women, have a screening test regardless of what their risk appears to be. Anyone who is concerned about being infected with HIV can request to be tested. Such testing is confidential and often free of charge.
The current combination screening test tests for two things that suggest HIV infection:
-
to HIV
-
HIV antigens
Antibodies are proteins produced by the immune system to help defend the body against a particular attack, such as that by HIV. Antigens are foreign substances that can trigger an immune response.
The body takes several weeks to produce enough antibodies to be detected by the test, so results of the antibody test are negative during the first few weeks after the virus enters the body . However, results of the p24 antigen test can be positive as early as 2 weeks after the initial infection. The combination tests can be done quickly by a laboratory. Also, a version of these tests can be done in a doctor’s office or clinic . If results are positive, doctors do a test to distinguish HIV-1 from HIV-2 and a test to detect the amount of HIV RNA in the blood .
Other, older rapid bedside tests are also available. These tests can be done using a sample of blood or saliva. If results of these rapid screening tests are positive, they are confirmed by ELISA or by repetition of one or more other rapid tests.
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Hiv And Your Complete Blood Count
If you have HIV, your healthcare provider will routinely perform blood tests to evaluate the status of your immune system and the level of viral activity in your body .
In addition to these tests, others will be performed to monitor for side effects or medical issues arising from the infection itself. Central to this is a panel of tests called the complete blood count . The test measures the composition of cells in a sample of blood to flag for changes that fall outside of the “normal” range of values.
By doing so, a CBC can reveal if an infection is developing or if an antiretroviral drug like AZT is causing anemia.
A CBC measures constituent cells in your blood, including white blood cells , red blood cells , and platelets . The test is typically ordered every three to six months but may be ordered more frequently if there is an active infection or illness.
Hiv Weakens Your Immune System
HIV attacks your white blood cells. White blood cells are the cells in your body that fight infection and keep you healthy. If you have HIV, your white blood cell count gets low and your body cant fight infection effectively.
HIV generally has three stages. The first stage is an acute HIV infection. Symptoms develop two to four weeks after infection occurs, and can appear like the flu. During the first stage, theres a high amount of the HIV virus in your blood and the virus is very contagious.
The second stage is HIV inactivity. This stage can last anywhere from 10 years to several decades if youre taking medicine to treat HIV. There may not be many symptoms during this stage, but you can still transmit the disease to others.
Stage three of HIV is AIDS. People with AIDS have extremely weakened immune systems and suffer an increasing number of illnesses and infections.
If left untreated, HIV can progress quickly and develop into AIDS in just a few years. There are a number of medications that can slow the progression of HIV, improving your health and quality of life for many years.
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