The Pathophysiology of Acquired Immune Deficiency Syndrome by Human Immunodeficiency Virus Brandon...

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  • The Pathophysiology of Acquired Immune Deficiency Syndrome by Human Immunodeficiency Virus Brandon Toy Mississippi College Graduate Seminar
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  • Virus Classification Group VI Virus All use virally encoded RNA-Dependent DNA Polymerase Reverse Transcriptase Family: Retroviridae Enveloped virus Contains single-stranded RNA Stores nucleic acid in mRNA genome Positive Sense RNA Genus: Lentivirus Longer incubation period HIV-1 & HIV-2
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  • Attachment Where does it attach? Virus attaches to the immune system cell, the dendritic cell found in the mucosal areas Transported by the lymphatic system to lymph nodes where other cells become infected Replication occurs primarily in activated CD4+ T Lymphocytes and to lesser extent in macrophages and dendritic cells
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  • Attachment Receptor Binding Receptor Bindings The two major glycoproteins involved with HIV receptors are gp120 and gp41 gp120 Binds to CD4 receptor Conformational change occurs and binding occurs to CCR5 or CXCR4 Cytokine Receptor CCR5 T cells and Monocytes Most important co-receptor CXC Chemokine Receptor Integral Membrane Protein Bind and respond to chemokines G Protein Receptor, 7-TMD CXCR4 known as fusin HIV predominantly T-Cells
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  • Attachment Chemokine binding causes gp120 to move and gp41 to bind gp41 Hydrophobic HR1 binds to membrane and HR2 zips into the groves of H1, pulling the virus closer, forming a large pore for the virus to enter Extremely stable bond
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  • Attachment Viral nuclear capsid enters the host cell 3 enzymes, 2 RNA strands are released Protease Cleaves protein strands into their smaller, active form Integrase carries viral DNA into the nucleus and integrates dsDNA into host DNA Reverse Transcriptase transcribes viral RNA into viral dsDNA
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  • Replication/Transcription Once the virus inside, the cell replicates virus Reverse Transcription Causes the most mutations leading to resistance Primary genes are p51 & p66 Finger, palm, thumb region protein structure Must be in closed form to transcribe Two Primary Active Sites Polymerase active site transcribes RNA/DNA double helix from viral RNA Ribonuclease H active site breaks down the RNA and DNA Polymerase completes the double stranded replication forming double stranded DNA
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  • Integration Preintegration Complex Viral dsDNA imported into cell nucleus through the nuclear pore Contains both viral and cellular proteins Integrase and other cofactors used Integrase cleaves dinucleotides from 3 end and forms sticky ends Integrase carries into the host nucleus and sticks into host DNA Host polymerase fils in complementary base pairs 3 OH group of 5 phosphorous Magnesium ions hydrolyze 3 end exposing new OH groups 5 bp apart, nicks DNA Host ligase and other cellular enzymes repair the single gaps Two unpaired nucleotides at the 5 ends of viral DNA removed Integrated DNA known as proviral DNA
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  • Integrase Protein Cleavage of 3 sticky ends Integrase Carrying DNA into host nucleus
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  • T-Cell Ribosomal Transcription Activation of the infected cell will cause transcription of pro- viral DNA into viral mRNA Ribosomes at the rough endoplasmic reticulum synthesize HIV envelope proteins first which are directed to the host membrane The same ribosomes build the poly protein chains that contain a total of two RNA viral strands per virus
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  • Integration Protease cleaves larger proteins into smaller core proteins Protease cleaves the poly-protein strand and the interior structures Env Pol Gag
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  • Genetics Env genes encode the precursor 160 140 kDa glycoproteins cleaved into gp160 and gp 140 respectively. Nucleocapsid proteins formed P24 capsid protein P17 matrix protein P7 nuclear protein Pol genes code for the viral enzymes (polymerase reverse transcriptase, integrase, protease) Precursor protein cleaved into P31 P51 p66 Gag genes code for the cone shaped viral capsid
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  • Genetics Other genes include Tat Influences function of genes distance away. Controls transactivation of HIV protein Rev Regulates expression of virus protein Vif virus infectivity factor gene; Required for infectivity as cell- free virus Nef Regulator that attenuates HIV replication Vpr R gene. Has an undetermined function
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  • Genetic Classification of HIV HIV-1 Vpu gene U gene required for efficient viral replication and release Only found in HIV-1 HIV-2 VpX gene has an undetermined function Only found in HIV and SIV (Simian Immunodeficiency Virus)
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  • Formation Two viral RNA strands and the replication enzymes are surrounded by the smaller core proteins. Final assembling around them forming the capsid Once complete, the virus leaves Obtains part of the host membrane for cell recognition Leaves as an immature virus Matures after leaving cell
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  • Initial Body Response Acute Illness Viral load increases and CD4 cells drop Can test for p24 antigen or HIV-RNA Host develops HIV antibodies A newborn less than 18 months old will have mothers antibodies so any test would be inaccurate Seroconvert
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  • Initial Immune Response Returns to the viral set point Several million virus particles per mL of blood will cause a drop in CD4 cell count CD8 killer T cells destroy the virus and HIV infected cells May also produced b-chemokine that competitively inhibit HIV attachment and down-regulate the HIV co-receptor and chemokine receptor proteins (Kinter et al. 1998; Saha et. al, 1998)
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  • Clinical Latency Latent period Chronic phases can occur. Basically an asymptomatic HIV infection Viral replication continues to occur during latent period, continual replication still occurs Period can last for several years
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  • Constitutive Period Towards the end of the latent period, viral load will increase. Massive increase in viral load will cause a complete elimination of CD4 cells Will lose the ability to regenerate new T-cells Resources of the T-cells have been overtaken by the synthesis of HIV Cell cannot develop its own required proteins
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  • Acquired Immunodeficiency Syndrome CD4 T cell count below 200/uL Average, healthy CD4 T-Cell Count between 500-1500/uL High Viral Load Opportunistic Infections Due to Attenuated Immune System Tuberculosis AIDS Dementia Complex AIDS Wasting Syndrome Hepatitis A & B Pneumocystis Pneumonia Cytomegalovirus Vision Loss Cancer risks less than 500/uL Kaposils Sarcoma Non-Hodgkins Lymphoma
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  • Clinical Tests ELISA & Simple/Rapid Tests Detects anti-HIV antibodies Gp120 antibodies present in all infected patients Western Blot Assay Nucleic Acid and Antigen Screen Tests Viral Load Test Low viral load below 10,000 copies High viral load more than 10,000 copies
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  • Pharmacology Fusion inhibitors Nucleoside Reverse Transcriptase Inhibitors Non-Nucleoside Reverse Transcriptase Inhibitors Integrase Inhibitors Protease Inhibitors
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  • Fusion Inhibitors Three gp120 subunits mediate receptor and co-receptor attachment Three gp41 subunits response for membrane fusion Receptor antagonists prevent gp120 attachment to the receptor and co-receptors gp41 conformation can be inhibited Enfurvitide Only approved fusion inhibitor Peptide based Competitively binds to gp41 and blocks the formation of the post- fusion structure Several other gp41 & gp120 inhibitors are being developed
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  • Abbreviated NRTIs Analogs of deoxyribonucleosides Lack a 3 OH group NRTIs must be metabolically converted by host cell kinases to corresponding triphosphate form NRTI-TPs inhibit reverse transcription by acting as chain-terminator Clinically Approved NRTIs ddI TDF ddC 3TC FTC AZT d4T Nucleoside Reverse Transcriptase Inhibitors
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  • Abbreviated NNRTIs Treat HIV-1 Infection Do not require intracellular metabolism for activity Hydrophobic Compounds Interact with HIV-1 RT Binds to site on p66 subunit of the HIV-1 RT p66/p51 heterodimer Also known as the binding pocket Non-Nucleoside Reverse Trasncriptase Inhibitors
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  • Raltegravir diketo acid (DKA) moiety with potent and selective inhibi- tory activity against the strand transfer step of integration Known as strand-transfer inhibitors Can uncouple the two integrase reactions Can block strand transfer without affecting 3 processing Thought that strand-transfer inhibitors bind at the interface of the integrase-metal cofactor Chelating the divalent metal, interfering with the binding of the chromosomal target DNA Integrase Inhibitors
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  • Peptide-like chemicals Competitively inhibit the action of the enzyme aspartyl protease Bind to the site where protein cutting occurs Proteolytic cleavage of the polypeptide precursors inhibited Cannot form into mature enzymes and structural proteins Gag & Pol proteins Protease Inhibitors
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  • Research/Development RT leads to Mutation Vaccine Neutralizing Antibodies (Nabs) Preventing initial receptor engagement events for binding Binding after attachment and inhibiting fusion process Nucleotide Reverse Transcriptase Inhibitor Tenofovir (Tenofovir Disoproxil Fumarate) First nucleotide reverse transcriptase inhibitor Nucleoside RTI must undergo three intracellular phosphorylation steps Nucleotide Reverse Transcriptase Inhibitors only require two steps Could produce more rapid and complete conversion of drug to pharmacologically active form
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  • Work Cited Alimonti, Judie B., T. Blake Ball, and Keith R. Fowke. "Mechanisms of CD4+ T lymphocyte cell death in human immunodeficiency virus infection and AIDS." Journal of general Virology 84.7 (2003): 1649-1661. Appay, V., and D. Sauce. "Immune activation and inflammation in HIV1 infection: causes and consequences." The Journal of pathology 214.2 (2008): 231-241. Blanpain, Cdric, et al. "CCR5 and HIV infection." Receptors and Channels 8.1 (2002): 19-31. Boehringer Ingelheim, 2007. Film. 30 Sep 2013.. Brunton, L.L., Lazo, J.S. and Parker, K.L. (2006) Goodman and Gilmanss The Pharmacological Basis of Therapeutics (11th edition). United States of America: McGraw-Hill. Burton, Dennis R., et al. "HIV vaccine design and the neutralizing antibody problem." Nature immunology 5.3 (2004): 233-236. Levin, Aviad, et al. "Peptides that bind the HIV1 integrase and modulate its enzymatic activitykinetic studies and mode of action." FEBS Journal 278.2 (2011): 316-330. Pierson, T. C., and R. W. Doms. "HIV-1 entry and its inhibition." Cellular Factors Involved in Early Steps of Retroviral Replication. Springer Berlin Heidelberg, 2003. 1-27. Pommier, Yves, Allison A. Johnson, and Christophe Marchand. "Integrase inhibitors to treat HIV/AIDS." Nature Reviews Drug Discovery 4.3 (2005): 236-248. Pyrko, Peter, et al. "HIV-1 protease inhibitors nelfinavir and atazanavir induce malignant glioma death by triggering endoplasmic reticulum stress." Cancer research 67.22 (2007): 10920-10928. Reeves, Jacqueline D., and Robert W. Doms. "Human immunodeficiency virus type 2." Journal of General Virology 83.6 (2002): 1253-1265. Richman, Douglas D. "HIV chemotherapy." Nature 410.6831 (2001): 995-1001. Sluis-Cremer, Nicolas, and Gilda Tachedjian. "Mechanisms of inhibition of HIV replication by non-nucleoside reverse transcriptase inhibitors." Virus research 134.1 (2008): 147-156. Suresh, P., and A. Wanchu. "Chemokines and chemokine receptors in HIV infection: role in pathogenesis and therapeutics." Journal of postgraduate medicine 52.3 (2006): 210. Temesgen, Zelalem, and Dawd S. Siraj. "Raltegravir: first in class HIV integrase inhibitor." Therapeutics and clinical risk management 4.2 (2008): 493. Unutmaz, Derya, et al. "Cytokine signals are sufficient for HIV-1 infection of resting human T lymphocytes." The Journal of experimental medicine 189.11 (1999): 1735-1746.