Hiv Pathophysiology

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Pathophysiology of the human immunodeficiency virus
Nancy R. Calles, MSN, RN, PNP, ACRN, MPH Desiree Evans, MD, MPH DeLouis Terlonge, MD

Objectives
1. 2. 3. 4. 5. Provide an overview of the healthy immune system. Describe the human immunodeficiency virus (HIV). Describe the major components of the HIV life cycle. Identify the various HIV types and subtypes. Discuss HIV’s effects on the immune system.

Overview
The human immunodeficiency virus (HIV) is a retrovirus belonging to the family of lentiviruses. Retroviruses can use their RNA and host DNA to make viral DNA and are known for their long incubation periods. Like other retroviruses, HIV infects the body, has a long incubation period (clinical latency), and ultimately causes the signs and symptoms of disease, here AIDS. HIV causes severe damage to the immune system and eventually destroys it by using the DNA of CD4+ cells to replicate itself. In that process, the virus eventually destroys the CD4+ cells.

Key Points
1. The immune system protects the body by recognizing invading antigens on pathogens (bacteria, viruses, fungi, and parasites) and reacting to them. 2. T lymphocytes, or T cells, regulate the immune system and destroy antigens. 3. HIV continuously uses new host cells to replicate itself. 4. The HIV life cycle includes six phases: binding and entry, reverse transcription, integration, replication, budding, and maturation. 5. Once HIV is in the circulatory system, it targets the CD4+ lymphocyte. 6. Two types of HIV cause AIDS: HIV type 1 (HIV-1) and HIV-2. 7. Primary infection refers to the time when HIV first enters the body. 8. Clinical latency refers to the time before onset of symptoms and complications in the HIV-infected individual. In HIV-infected adults, this phase may last 8-10 years. 9. Early signs and symptoms of HIV can include candidiasis, lymphadenopathy, cervical carcinoma, herpes zoster, and peripheral neuropathy. 10. Late signs and symptoms of HIV and AIDS-defining illnesses can include the development of lifethreatening infections and malignancies.

The Healthy Immune System
The immune system protects the body by recognizing antigens on invading bacteria and viruses and reacting to them. An antigen is any substance that induces a state of sensitivity and immune responsiveness. These antigens interact with antibodies and immune cells, initiating an immune response. This process destroys the antigen, allowing the body to be free of infections. Types of antigens include bacteria, viruses, fungi, and parasites. When the immune system is weakened or destroyed by a virus such as HIV, the body is left vulnerable to infections. The immune system consists of lymphoid organs and tissues, including the bone marrow, thymus gland, lymph nodes, spleen, tonsils, adenoids, appendix, blood, and lymphatic vessels (Figure 1). All components of the immune system are vital in the production and development of lymphocytes, or white blood cells. B lymphocytes (or B cells) and T lymphocytes (or T cells) are produced from stem cells in the bone marrow. B cells stay in the bone marrow to complete the maturation process, but T lymphocytes travel to the thymus gland to complete their maturation. There T lymphocytes become immunocompetent, multiply, and become more differentiated.

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HIV Curriculum for the Health Professional
cells, T-suppressor cells, inhibits or suppresses immune responses. Normal CD8+ cell count is between 300 and 1,000 cells in adults and children. The normal CD4+:CD8+ ratio is between 1.0 and 2.0. T cells can secrete cytokines (chemicals that kill cells), such as interferon. Cytokines can bind to target cells and activate the inflammatory process. They also promote cell growth, activate phagocytes, and destroy target cells. Interleukins are cytokines that serve as messengers between white blood cells. Recombinant (laboratory synthesized) interleukins are currently being studied in clinical trials for patients with HIV infection....
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