Abnormal Immunity Continued

Do Now: A large number of people in NYC are infected with HIV for months or years before being tested to find out they are HIV-positive. Many people who discover they are HIV-positive are shocked and surprised about the fact. Why do you think that is so?

AIDS Acquired Immunodeficiency Syndrome (AIDS) AIDS is not inherited, it is acquired by infection with HIV (Human Immunodeficiency Virus) Simple virus with only 9 genes that encode for 15 proteins, yet it affects more than 200 human proteins as it invades the immune system

HIV Infection Virus enters T cell & impairs first line of defense Virus adheres using its own surface proteins that bind to 2 receptors on host cell surface After binding, cell surface contorts in a way that allows virus to enter cell

HIV Infection Once virus is inside the host T cell, reverse transcriptase copies viral RNA into DNA which replicates to form the DNA double helix process is mainly associated with retroviruses (viruses that insert a copy of their genome into the host cell)

HIV Cell Production Newly formed viral DNA enters host T cell nucleus Virus “hijacks” cells reproductive machinery → viral genes are transcribed and translated Host T cell fills with viral pieces that assemble into particles and eventually bud off from host cell

HIV Progression After HIV invades host, helper T cells start to die at a high rate B cells cannot be activated to produce antibodies without the T cells, bacterial infections begin in host Overtime, the virus can change & eventually bind to Killer T cells (kills cells). Loss of Killer T cells renders the body very vulnerable to infection & cancer

How HIV Changes HIV replicates and changes quickly The virus mutates easily because it cannot repair replication errors that happen frequently due to the “sloppiness” of reverse transcriptase in copying viral RNA to DNA Immune system cannot keep up, antibodies previously made for virus are useless against its next variant or mutation

Treatment for HIV Prescribing drugs with different actions is the most effective way to slow the constantly changing virus into a chronic, lifelong illness Combination of these various drugs is why we call HIV treatment medications a “cocktail of drugs” Start here genetics 1

Treatment for HIV Drugs work by blocking binding action of virus to T cells, blocking entry of virus into T cell, slowing replication and assembly of viral proteins Clues to developing new HIV drugs come from people at high risk who resist infection → look for variations in the DNA of people who had high risk habits, yet never became infected