HIV: A 60 Year RetrospectiveNRTIPINNRTIDisease ProgressionClinical PictureModes of Horizonal TransmissionAlso Vertical Transmission!(11-60% depending on severityof maternal infection and±breastfeeding)Incidence and Prevalence• 36.1 million worldwide are infected• Another 21.8 million have died• 13.2 million children currently are “AIDS Orphans”• 14,000 new infections daily (5.3 million in 2000)• 70% of cases in sub-Saharan Africa where seroprevalence can exceed 25%• Caribbean, Southeast Asia and Eastern Europe are other trouble areasVirus TaxonomyHIV belongs to the lentivirus subclass of retroviruses• 2 copies of the +RNA strand; goes through a dsDNA intermediate• icosahedral capsid• enveloped• 80-130 nm virionHIVSootey MangabeySykes MonkeyChimpanzeeAfrican Green Monkeyvisna/maedicaprine arthritis-encephalitisMandrillequine infectious anemiafelinebovineThe Lentiviruses (slow viruses)1959 Serum from Bantu Male @ Kinchasa DRC => ZR59Suggests single trans-species jump in 1940-1950 and radiation after WWIIYBF30 is a sequence outlier isolated from a patient in CameroonHuman Immunodeficiency VirusesGroups and CladesMap of HIV Natural ReservoirsKeele et al. Science 313: 523-6 (2006).SIV appeared after versus/velleroses (0% prevalence) split from troglodytes/schweinfurthi (25-35% infected)Anatomy of a Retrovirus-NEF AttenutationProteinsOTHER VIRALLY EXPRESSED PROTEINS:• tat - transcription elongation factor, regulates gene expression.• rev - nuclear export of unspliced RNA.• nef - “negative factor”, down regulates surface CD4 and MHC I.• vif - blocks cytidine deamination, an innate defense against retroviruses. Harris et al. Cell 113: 803-9 (2003)• vpr - arrests cell cycle in G2, promotes DNA entry into nucleus.• vpu - ER resident TM protein, facilitates virus release, traps CD4.MAJOR PROTEINS:• gag - membrane association, assembly, budding• pol - reverse transcriptase.• int - integrase.• env - envelope glycoprotein.Viral Replication Cycle• 109 copies/day in fulminant AIDS• Genome is ~104 nucleotides• RT error rate is 10-4 to 10-6• Every single-base mutation of the genome occurs at least once per day per patientmolecular intervention: RT and protease …RT InhibtorsNucleoside:Non-Nucleoside:Protease InhibitorsRetroviral Drug Resistance in New PatientsLittle et al. New Eng. J. Med. 347(6): 385-94 (2002).TibotecKing et al. Chem. and Biol. 11: 1333-8 (2004).Where Else to Attack?molecular intervention: fusion …The Model for Viral FusionEnfuvirtideHIV Association with Targets• CCR5 Homozygous Mutants are HIV resistant and otherwise healthy• RANTES (CCR5 ligand) promoter overexpression mutants are HIV resistant• Sdf-1 (CXCR4) overexpressors are HIV resistantChoe et al. Cell 85: 1135-48 (1996).Preventing HIV Entry• PRO542 (Progenics): gp120 tetramer to IgG Fc that blocks CD4-gp120 interaction• BMS-806 (Bristol-Myers Squibb): small molecule that targets the CD4 binding site on gp120• TNX-355 (Tanox): an anti-CD4 antibody• SCH-C, SCH-D (Schering-Plough) and UK-427,857 (Pfizer:) block CCR5• AMD3100, AMD070 (AnorMED): block CXCR4Maraviroc, FDA 8/2007molecular intervention: integration …HIV Integrase InhibitorsMerck MK0518• Two log reductions in viral load• Kinetics of viral decrease faster than thought possible (cellular reservoirs)Hazuda et al. Science 305: 528-32 (2004).a vaccine? …HIV Vaccine• >50 preparations have entered clinical trials (HIV Vaccine Trials Network)• 1997 Clinton’s HIV vaccine challenge: 10 years• NIH currently spends >500 million/year on trying to find an HIV vaccine• NOTHING! (punctuated equilibrium)• Do aspects of the immune response facilitate HIV pathogenesis?1984-1994: Search for sterilizing vaccine by subunit/alum approach.Early 1990's: Ab's and soluble CD4 work in lab but not on primary HIV-1 isolates.Humoral vaccine programs put on hold.1990-2007: Attempt to produce an adenovirus based T-cell vaccine.2006: Prospective Amsterdam study shows that strong HIV-specific memory T-Cellresponse does not afford any protection (maybe even a liability).2007: The STEP and Phambili trials with MRKAd5 Trivalent HIV vaccine (gag, pol, nef)are cancelled because of lack of efficacy.The case for Cell-Based VaccinesViremia Survival Memory CD4+ T-CellsLetvin et al. Science 312(5779): 1530-3 (2006).Broadly Neutralizing Antibodies•mAB b12: convex recombining site• 447-52D: V3 GPGR motif and main-chain (MHC)• mAb 2G12: domain-swap binds oligomannose•2F5, 4E10: TM epitopesBurton et al. Proc. Natl. Acad. Sci. 102(42): 14943-8 (2005).The Case for a Sterilizing Humoral VaccineB12 (vaginal or IV) protects monkeys from infection.Many of the broadly neutralizing antibodies recognize parts of gp120 that bind to CD4.The Case for a Tolerizing VaccineINFLAMMATION CORRELATES WITH DISEASE PROGRESSION!HIV-1 induces a systemic immune response, primarily to bacterial antigens; the level of this immune activation at the viral setpoint is the best current predictor for disease progression."Elite Controllers" exhibit a lower level of systemic immune activation.SIV infects sootey mangabeys but does not cause AIDS; the system immune activation/inflammation is alsonot observed.The frequencet fo mother-child transmission of HIV-1 is lower than might be expected; doesimmunosupression during pregnancy account for this observation?Brenchley et al. Nature Medicine 12: 1365-1371 (2006).Restriction factors …Trim5αStremlau et al. Nature 427: 848-53 (2004).Stremlau et al. Proc. Natl. Acad. Sci 103: 5514-9 (2006))Kaiser et al. Science 316:1756-8 (2007)HIV-1 infects New World monkey cells, but not Old World monkeys: Why?Put rhesus cDNA library into HeLa cells and infect with GFP-labeled HIV virus.Get one clone, TRIM5α.A species restriction factor that is an E3! (J. Vir. 79(14): 8870-8877 2005)Appears to cause premature uncoating of the HIV capsid (why this is a problem is unknown).Human TRIM5a may have evolved away from chimpanzee in order to suppress a now-extinctretrovirus, PtERV1 (resurrection experiments).Apobec 3GHarris et al. Cell 113: 803-9 (2003)Vif- virus replicates in HeLa, COS, Jurkat, 293T cells but not in H9 or CEM15 cells.Non-permissive phenotype dominant in cell fusion experiments => inhibitor.Apobec 3G cloned as the inhibitor by a subtractive mRNA screen in 2002.Vif overcomes the restriction imposed by Apobec3G.Cytidine deaminase enzyme; related to AID enzyme of somatic hypermutation.Part of