8-4: HIV
Latent vs. Active Infection
A latent infection is the period of time between the presence of the provirus and the active replication of viral components. An active infection is when 1) proviral DNA is transcribed; 2) viral components are made; 3) viruses are assembled; and 4) newly made HIV are released through a process called budding.
What's the difference between being HIV positive and having AIDS?
A person who is infected with the human immunodeficiency virus is considered HIV positive. A person with a CD4 count lower than 200 cells per cubic millimeter or with an HIV-related opportunistic infection has AIDS.
The Human Immunodeficiency Virus (HIV)
The Human Immunodeficiency Virus has an outer phospholipid envelope, which allows the virus to attach onto the host cell using a structure called the docking glycoprotein 120 (gp 120). Underneath the envelope is the capsid. The capsid is a protein coat that protects the genetic material, which consists of segments of viral RNA.
Stage 1: Acute Infection
The acute-infection stage, also called the primary-infection stage, is the initial stage of the infection. It is often accompanied by a short, flu-like illness. During this stage, large amounts of the virus are produced in the body, destroying CD4 cells (a type of T-cell) in the process. The immune system responds to this invasion by producing antibodies that kill antigens and killer T cells that kill antigen-infected cells.
Stage 2: Clinical Latency
The clinical latency stage is also called the asymptomatic stage because during this stage, the virus is reproducing in the body, but without causing any symptoms. This symptom-free stage can last 10 years or more.
Attachment
The host cell for HIV is a type of leukocyte (white blood cell) called a T cell, which is important for immune responses. One type of T cell has a receptor on its surface. These surface cells are called CD4 cells or T-helper cells. These "helper" cells initiate the body's response to antigens. Their main role is to send signals to other types of immune cells, including those that destroy the infectious agent. HIV docks to the T cell by attaching to the CD4 receptor.
What happens when HIV fuses with the T cell?
The viral RNA enters the T cell.
Unprotected Sex
Unprotected sex means having sex without using a condom. Unprotected sex is by far the most common mode of HIV transmission.
What is assembled in the cytoplasm of a T cell?
Viral components are assembled.
What is a provirus?
a mixture of viral and host-cell DNA
Why is HIV classified as a retrovirus?
because its genetic material is RNA
Stage 3: AIDS
AIDS is the final stage of an HIV infection. At this stage, the immune system is severely damaged due to the high amount of HIV and the low CD4 cell count. By this stage, HIV has destroyed so many of the CD4 cells that the body cannot fight infections anymore, which puts the person at risk for opportunistic infections. Opportunistic infections are caused by pathogens that a healthy immune system is usually able to fight. In a person with HIV, infections are able to take advantage of the body's weakened immune system, causing diseases that can affect nearly every organ system in the body. An infection is considered to have progressed from HIV to AIDS when the number of CD4 cells falls below 200 cells per cubic millimeter of blood (200 cells/mm3). In healthy adults, CD4 counts are between 500 and 1500 cells/mm3. An additional indicator that the infection has progressed from HIV to AIDS is that the person develops one or more HIV-related opportunistic diseases. Recall that AIDS stands for Acquired Immunodeficiency Syndrome. A is for Acquired: AIDS is acquired, not inherited. I is for Immuno: AIDS damages the body's immune system. D is for Deficiency: AIDS occurs when the immune system is deficient and unable to do its job. S is for Syndrome: AIDS is not a single disease, it is a syndrome, which is a collection of symptoms and signs of disease.
In general, are caregivers at risk of getting an HIV infection when taking care of an HIV-positive infant?
As long as they do not come in direct contact with the infant's blood, caregivers are not at risk of getting an HIV infection when caring for an HIV-positive infant.
Integration
Before entering the nucleus of the T cell, the viral DNA (shown in red) becomes double stranded. The double-stranded viral DNA joins the T cell DNA (shown in blue) in a process called integration. The result is a provirus, which is a mixture of viral and T cell DNA. A provirus is capable of replication.
Describe how HIV can cause the body to lose its ability to fight infections.
HIV attaches to the T cells. Once the T cells are infected by the virus, they work to create new viruses instead of fighting infections, which is the job they are supposed to do in the immune system. In addition, the virus reproduction process destroys many of the T cells.
HIV docks onto what part of the T cell?
HIV docks onto the CD4 receptor.
What type of cell does HIV use as a host?
HIV uses a type of T cell called a helper T cell as its host.
How can an adult lower his or her risk of getting HIV?
He or she could refrain from having unprotected sex and from sharing drug needles.
What is the function of the helper T cells in the body?
Helper T cells send out signals to other types of cells, including those that destroy the infectious agent.
HIV
Human Immunodeficiency Virus, or HIV, which is the virus that causes Acquired Immunodeficiency Syndrome, or AIDS.
Injection Drug Use
Injection drug use is the use of a hollow needle and a syringe to introduce a drug into the body. People who are injection drug users (IDUs) can get HIV from sharing needles with a person who has HIV. Injection drug use is responsible for about 10% of annual HIV cases.
What is the result of integration?
Integration results in a provirus.
Reverse Transcription
Most organisms have DNA as their genetic material. However, some viruses, such as HIV, have RNA as their genetic material. This difference is why HIV is classified as a retrovirus. HIV uses the viral RNA to make complementary DNA (cDNA) in a process called reverse transcription. This process is considered reversed because normally DNA is used to make messenger RNA (mRNA).
Mother-to-child transmission
Mother-to-child transmission of HIV is the spread of HIV from an HIV-infected woman to her child during pregnancy, childbirth, or breastfeeding. The rate of HIV-positive mothers infecting their unborn children has been decreasing due to changes in the way hospitals and clinics now treat pregnant women. Hospitals routinely test pregnant women for HIV and administer ART to pregnant women who are HIV positive. These actions may prevent a mother from transmitting the virus to her unborn child.
What buds out of the T cell?
Newly made HIV bud out of the T cell.
Fusion
Once HIV has docked to the T cell, its viral envelope fuses with the surface of the T cell. This fusion allows the viral RNA to enter the T cell.
What is reverse transcription?
Reverse transcription is when DNA is made from RNA.
How can a mother with HIV lower the risk of transmitting the infection to her newborn baby?
She can take ART and avoid breastfeeding the baby.
Based on what you know about viruses, what happens to T cells when HIV uses them as a host?
T cells are destroyed when the virus uses them to make copies of itself.
Some drug users avoid using needles to administer the drug to the body. However, they are still at a higher risk of contracting HIV than people who do not use drugs. Explain.
Taking drugs affects a person's ability to make wise choices, so a person who is using drugs is at a greater risk of having unprotected sex, by which they could contract HIV.
