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Midterm 3 Study Guide

Midterm 3 Study Guide - Midterm#3 Notes HIV Targets and the...

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Midterm #3 Notes HIV Targets and the Immune System - Immune system failure o Bacterial: Toxic shock: bacterial infection of blood resulting in an overaggressive response from the immune system Mycobacteria tuberculosis: immune system is unable to completely clear TB without antibiotics o Viral: Herpes: remains latent in neurons waiting for opportunities to reinfect (chicken pox, leads to shingles) Very aggressive viruses: Ebola, Hantavirus - Places where the immune system attempts to stop HIV o Antibodies: first stop Antibodies recognize proteins, carbohydrate, lipids HIV envelope proteins hide from antibodies; HIV uses cellular machinery decorates gp120 with random carbohydrates our immune systems don’t recognize these and prevent antibodies from correctly identifiny HIV envelope proteins change rapidly (mutations) Reverse transcriptase: o Makes many mistakes: 1 to 5 each time; replicates HIV RNA to DNA; Cannot correct these mistakes; each virus can be different from the last HIV has a high production rate o Produces 1 – 10 billion viruses per day (those many different viruses) Antibodies lose their ability to bind to HIV Parts of gp120 that are visible to antibodies can be very rapidly changed thru mutation Antibodies thus have a hard time binding to new versions of gp120; always one step ahead of antibody generation o Gene splicing: second step; will try to ‘silence’ the production of the HIV gene Epigenetics: inheritable genetic changes not at the DNA sequence level; host cells try to keep viral genes from being transcribed Modification of HIV DNA: host cell will modify HIV DNA via methylation; this ‘mark’ recruits a protein preventing transcription Modification of chromatin around HIV DNA Enhances latency phase of the infection (good for infected, bad for pandemic/treatment) o Destruction of RNA: cells attempt to trap and destroy HIV mRNA Unspliced RNA All host mRNA gets modified in a process called ‘splicing’ Viruses need mRNA to be unspliced since it’s in their genome
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Host cells have figured this out, will attempt to trap/destroy unspliced RNA and keep viruses from replicating HIVs’s solution: protein Rev binds HIV mRNA and escorts it out of the nucleus and protects it from degredation o Destruction of infected cells Infected cells usually notify CD8 T cells that they’re infected Controls HIV in early stages of infection; HIV would rather decide when the infected cell dies - HIV contains Nef which kills the MHC messenger; no MHC so nothing to bind to - HIV can mutate to hide from CD8 T cells o Mutation of single amino acid in MHC Class I; surface proteins are then not recognized and it happens to go through o Can mutate other amino acids and so peptide no longer sticks to MHC; T cells come by and see nothing wrong and thus it goes unattacked - HIV always one step ahead of our immune systems o Natural selection: heritable traits make it more likely for an organism to survive
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