Chapter 2: The Path from HIV to AIDS

The Path from HIV to AIDS HIV infects only humans and creates a deficiency in the body’s immune system HIV belongs to a family of viruses called retroviruses Because retroviruses mutate very quickly, a person’s immune system does not have any defenses against the new version of the virus HIV is also a lentivirus – a virus with a long delay between initial infection and the time the infected person starts to show symptoms

The Structure of HIV-1 The Spikes: The complex proteins that protrude through the surface of the viral envelope The Capsid: The bullet shaped core of the HIV particle which surrounds two single strands of HIV’s genetic material Reverse Transcriptase: An enzyme that allows HIV’s RNA to change into DNA so that it can pass into the host cell’s nucleus to begin reproducing itself The Viral Envelope: The outer coat of the virus, which is composed of two layers of fat molecules

What Happens After HIV Infects Cells? Once in the body, HIV replicates and spreads widely 2-4 weeks after exposure, most HIV-infected people suffer flu-like symptoms, as their immune systems fight off the initial HIV infection This first immune response may dramatically reduce HIV levels As a result, the number of CD4+ T-cells in a person’s body may rebound after the first, acute infection

What Happens After HIV Infects Cells? (continued) The HIV+ person may then remain free of HIV-related symptoms for years The virus continues replicating Eventually, HIV overwhelms the person’s system and large quantities of the virus enter the blood stream

Why do HIV Infections Almost Always Progress to AIDS? HIV eludes the immune system so that the body stops fighting it HIV’s many mutations make some of its particles invisible to the body’s immune system HIV damages the immune system, so that the body can’t fight it Not enough healthy CD4+ cells to defend the body against infections When the immune system can no longer defend against opportunistic infections, the person has AIDS

Diagnosing HIV Infection Main Types of HIV Tests: ELISA (Enzyme-Linked Immunosorbent Assay): determines if HIV antibodies are present in blood or oral fluids Western Blot: A highly specific test that is used for confirming the ELISA test Rapid HIV tests: Saliva-, urine-, and home HIV antibody testing kits HIV RNA tests: Diagnose HIV infection very early, before antibodies are even formed

The Stages and Symptoms of HIV Disease Primary Infection: The first stage of HIV disease 2 to 4 weeks after infection, 87% of HIV+ persons suffer flu-like symptoms (acute HIV syndrome) It usually takes 6 to 12 weeks for the immune system to develop antibodies to fight the virus Seroconversion is the time when the body begins producing antibodies, this can take up to 6 months

The Stages and Symptoms of HIV Disease Chronic HIV Infection: Asymptomatic Period Also called clinical latency – person has no signs or symptoms of HIV disease Although individual shows no symptoms, the virus is actively multiplying and infecting and killing immune system cells Immune System Decline The more HIV a person has (the plasma viral load) the lower the number of CD4+ cells; ultimately results in the rapid decline of the immune system

Mild, Non-specific Symptoms: Immune System Decline Mild, Non-specific Symptoms: When the immune system is damaged, people begin to experience mild symptoms Swollen lymph nodes Fatigue Weight loss Frequent fevers and sweats Frequent or persistent yeast infections Persistent skin rashes Shingles

Immune System Decline (continued)

Advanced HIV Disease / Clinical AIDS The CDC has two different sets of criteria for diagnosing AIDS: Set 1—An HIV infection, confirmed by testing, plus a CD4+ T-cell count of less than 200 per cubic millimeter of blood Set 2—An HIV infection, confirmed by testing, plus one of 26 clinical conditions, primarily opportunistic infections that do not normally affect healthy people

Opportunistic Infections Infections that do not cause disease in people with healthy immune systems, for example: Pneumocystis Carinii Pneumonia (PCP) (a kind of pneumonia) Kaposi's Sarcoma (KS) (a kind of cancer) HIV wasting syndrome (extreme weight loss) Non-Hodgkin's lymphoma (a kind of cancer) HIV encephalopathy (AIDS Dementia) Candidiasis (Yeast Infection) of the trachea, bronchi, or lungs Candidiasis (Yeast Infection) of the esophagus